Property of American Airlines Maintenance · A. Cleanliness of the refrigeration system Absolute cleanliness is necessary in a refrigeration system in order to insure reliable and

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Table of Contents

March 2013 Table of Contents Proprietary/Confidential Page 31 © 2013 Twist, Inc.

CHAPTER/ TITLE SECTION PAGE 1: Introduction to Servicing Owner’s Responsibility ............................................................. 2 - 1............... 33 Preventive Maintenance........................................................... 2 - 1............... 33 Precautionary Measures .......................................................... 2 - 1............... 33 Operator Daily Inspection......................................................... 2 - 1............... 34 2. Safety Precautions General Precautions ................................................................ 2 - 2............... 35 Refrigerant Precautions ........................................................... 2 - 2............... 36 3. Refrigeration Basics and Service Theory...................................................................................... 2 - 3............... 37 Basic Cycle Explanation ................................................ 2 - 3............... 37 Fundamentals .......................................................................... 2 - 3............... 38 Cleanliness of the Refrigeration System........................ 2 - 3............... 38 Oil Refrigerant Mixture................................................... 2 - 3............... 39 Servicing System and Charging ............................................... 2 - 3............... 40 Gauge Manifold ............................................................. 2 - 3............... 40 Service Valves............................................................... 2 - 3............... 41 Removing Refrigerant.................................................... 2 - 3............... 41 Adding or Removing Oil................................................. 2 - 3............... 42 Dealing with Non-Condensable ..................................... 2 - 3............... 43 Refrigerant Leaks .......................................................... 2 - 3............... 43 Brazing Refrigerant Lines .............................................. 2 - 3............... 45 Pressure Testing ........................................................... 2 - 3............... 46 Evacuation..................................................................... 2 - 3............... 46 Charging........................................................................ 2 - 3............... 47

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Table of Contents

Table of Contents March 2013 Page 32 Proprietary/Confidential

© 2013 Twist, Inc.

CHAPTER/ TITLE SECTION PAGE 4. Introduction to Preventive Maintenance Checklists .................. 2 - 4...............49 5. Preventive Maintenance Quarterly Checklist............................ 2 - 5...............51 6. Preventive Maintenance Semi- Annual Checklist ..................... 2 - 6...............53 7. Preventive Maintenance Seasonal Checklist ........................... 2 - 7...............55 8. Adjustments Thermostats ............................................................................. 2 - 8...............57 Expansion Valve Superheat ..................................................... 2 - 8...............57 Hot Gas By Pass Valve Adjustment ......................................... 2 - 8...............58 9. Cleaning and Painting Filters ....................................................................................... 2 - 9...............59 Condensers.............................................................................. 2 - 9...............59 Evaporators and Ducts............................................................. 2 - 9...............59 Painting .................................................................................... 2 - 9...............60

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SERVICE Section 1: Introduction to Servicing

March 2013 2 –1 Proprietary/Confidential Page 33 © 2013 Twist, Inc.

1. Owner’s Responsibility

Ownership of PCA units supplied by Twist, Inc. imposes a duty upon the

Owner to maintain the integrity of the equipment. The objective of periodic maintenance is to ensure that the units are in the same condition and configuration as originally supplied by Twist, Inc. and to incorporate any changes directed by Twist, Inc. to assure the continued service life and safety of the product.

Maintenance must be performed on a routine basis in accordance with Twist,

Inc.’s recommended preventive maintenance checklists in this chapter to keep warranty coverage active. Replacement parts must conform to original equipment specifications.

Modification of the structural, electrical, mechanical, or safety components of

Twist, Inc. Pre-Conditioned Air units must be accomplished in strict accordance with Twist, Inc.’s specifications if performed by any party other than Twist, Inc.

Any questions which owners may have relative to the installation,

maintenance, or modification of Twist, Inc.’s products should be referred to Twist, Inc.

2. Preventive Maintenance

Rigidly adhering to a good program of preventive maintenance will prevent or

reduce failure or the need for corrective maintenance. Preventive maintenance includes recommended inspections, cleaning of designated components, and touch-up painting as required. Local conditions will determine to some degree the exact details of a good preventive maintenance program.

3. Precautionary Measures A. Exercise extreme care to insure that all repairs, installations, and

service are of the highest possible quality. Always use the proper tools for the proper job. Wipe clean all spills, smudges, smear, or dirt accumulation resulting from preventive maintenance exercises.

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B. General Considerations (1) Only trained personnel should work on the Twist Pre-Conditioned

Air unit. (2) Avoid hurried or careless workmanship. (3) Schedule work from start to finish without interruption to insure

no steps are overlooked.

(4) Maintenance or work done on the refrigeration systems must be done only by EPA certified personnel.

4. Operator Daily Inspection

A. The PCA unit operator should visually check to ensure that no loose, broken, or missing components exist on the unit. When connecting the supply air hose, ensure that the gasket and clamps is in good physical condition.

B. After confirming the overall operation of the unit, report any concerns

noted to the maintenance department for repair.

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Section 2: Safety Precautions

March 2013 2-2 Proprietary/Confidential Page 35 © 2013 Twist, Inc.

1. General Precautions WARNING: AVOID CONTACT WITH THE TOP OF A SCROLL

COMPRESSOR. COMPRESSORS BECOME HOT DURING NORMAL OPERATION.

WARNING: NEVER REMOVE THE COMPRESSOR FROM THE UNIT

WITHOUT REMOVING THE REFRIGERANT PRESSURE FROM BOTH THE HIGH AND LOW SIDE OF THE SYSTEM. FAILURE TO DO SO COULD RESULT IN SERIOUS INJURY OR DEATH, BECAUSE THE ESCAPING PRESSURIZED OIL AND REFRIGERANT MIXTURE COULD BE IGNITED BY THE TORCH FLAME.

NOTE: Since the compressor’s scroll flanks may seal the refrigerant

pressure between the high and low sides preventing pressure equalization through the compressor, remove the refrigerant charge from both the high and low side of the compressor before removing the compressor from the system.

Whenever performing work on the unit, turn off the external

power and ensure that all OHSA and/or company safety requirements are met.

NOTE: The actuator handle mounted on the control panel door is

equipped with provisions for inserting a lockout device when placed in the OFF position. Always lock the actuator handle "off" when working on the unit.

If the control panel door is open when the breaker handle

actuator is in the "ON" position, the safety switch will trip the circuit breaker shunt trip and turn the circuit breaker “OFF”. To work on the unit with the door open and to turn on the power, the safety switch can be pulled out to by pass the safety switch. The power then can be turned on. Use extreme caution when working on the unit with power ON.

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2. Refrigerant Precautions A. Eye Hazard - Liquid refrigerant may cause permanent damage if it

comes in direct contact with the eye due to rapid cooling. Whenever handling refrigerant, wear eye protection and keep face away from working area.

B. Inhalation - Inhaling high concentration of refrigerant may cause

lightheadedness, narcosis, and possible cardiac arrhythmia. Use adequate ventilation when handling refrigerants.

C. Toxic Products - Refrigerant by itself is very stable; however, at high

temperatures it may decompose to produce hydrochloric and hydrofluoric acid. In the presence of open flame, poisonous phosgene gas is produced.

WARNING: DO NOT BRAZE PIPING, WHICH HAS NOT BEEN PURGED OF

REFRIGERANT. THIS MAY RESULT IN AN EXPLOSION DUE TO THE OIL/REFRIGERANT MIXTURE.

D. Explosion - Refrigerant by itself is not flammable; however, it is stored

and shipped in pressurized containers. Containers should not be stored or heated above 125 degrees F, which creates dangerously excessive pressure in the container and possible explosion.

E. Burns - Body tissue may be damaged by freezing. Avoid contact of

liquid refrigerant with the bare skin since damages similar to burns may result.

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Section 3: Refrigeration Basics and Service


1. Theory The unit employs a vapor-cycle refrigeration system using a scroll type

compressor and refrigerant. A. Basic cycle explanation The following is a simplified description of the basic cycle starting at the

compressor: The compressor receives low-pressure refrigerant vapor and the

compressing process increases both the pressure and the temperature. The hot, high-pressure gas is forced from the compressor into the condenser. As the high-pressure gas passes through the finned condenser coil, it is cooled by outside air moved by motor-driven fans. As the temperature of the refrigerant vapor reaches the saturation point corresponding to the pressure in the condenser, the vapor condenses into a liquid and flows through the thermostatic expansion valve, which controls the feed of liquid refrigerant to the evaporator. It reduces the pressure of the refrigerant to the evaporator by means of an orifice.

The reduction of pressure on the liquid refrigerant causes it to boil or

vaporize until the refrigerant is at the saturation point corresponding to its pressure. As the low temperature refrigerant passes through the evaporator coil, heat from the air being conditioned flows through the walls of the evaporator tubing to the refrigerant, causing the boiling action to continue until the refrigerant is completely vaporized into a gas.

The expansion valve regulates the flow through the evaporator coil as

necessary to maintain a preset temperature difference (or superheat) between the evaporating refrigerant and the vapor leaving the evaporator. As the temperature of the gas leaving the evaporator coil varies, the expansion valve power element bulb senses its temperature and acts to modulate the feed through the expansion valve as required. The refrigerant vapor leaving the evaporator coil travels through the suction line to the compressor inlet. The refrigeration process starts over again and continues as long as the compressor is in operation.

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2. Fundamentals A. Cleanliness of the refrigeration system Absolute cleanliness is necessary in a refrigeration system in order to

insure reliable and trouble-free operation. Vapor cycle refrigeration systems are vulnerable to attack from two

common contaminants: air and moisture, which are not readily apparent in the system. If either or both are present in a system, they quickly join together in attacking the refrigerant and oil, causing corrosion, copper plating, acid formation, sludge, and other problems. When opening a refrigeration system for repair or component replacement, take extreme care to cover or cap open joints to prevent moisture from entering in the form of vapor, which is always contained in the outside air.

When copper tubing and fittings are brazed, copper oxide may form on

the inside of the tube unless nitrogen or dry CO2 is circulated through the tubing during the brazing operation. This oxide may become a powdered abrasive, plugging oil passages, scoring bearings, plugging refrigerant passages, plugging filters, and causing other problems. Taking reasonable care during service will keep contamination in a system at a safe and acceptable level.

Important rules of cleanliness:

Keep tubing clean and dry. Pass an inert gas through the tubing when brazing. Keep foreign materials out of the system when it is opened. Thoroughly evacuate the system after any exposure to the

atmosphere. Any time the system is to be opened, introduce a slightly positive

pressure to prevent air from rushing into the lines.

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B. Oil-Refrigerant mixture In vapor cycle refrigeration systems, oil and refrigerant mix

continuously. Refrigeration oils are soluble in liquid refrigerant, and at normal room temperatures they will mix completely.

Since oil must pass through the compressor scrolls to provide

lubrication, a small amount of oil is always circulating with the refrigerant.

Oil circulating in a refrigeration system may be exposed to both very

high and very low temperatures. Because of the critical nature of lubrication under these conditions and the damage that can be done to the system by impurities in the oil, use only the proper oil prepared for the refrigerant and the compressor.

One of the basic characteristics of a refrigerant and oil mixture in a

refrigeration system is the fact that refrigerant is attracted by oil and will vaporize and migrate through the system to the compressor crankcase even though no pressure difference exists to cause its movement. Upon reaching the crankcase, the refrigerant will condense into liquid, and this migration will continue until the oil is saturated with liquid refrigerant.

Upon start-up, excess refrigerant in the compressor crankcase may

result in violent foaming and boiling action, driving all of the oil from the crankcase and causing lubrication problems.

If excessive foaming is noted in the site glass, too much liquid has returned to the crankcase and the system must be taken out-of-service until a qualified technician can service the system. Failure to do so can severely damage the compressor, creating added work and considerable expense.

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3. Servicing System and Charging A. Gauge Manifold The most important tool of the refrigeration serviceman is the gauge

manifold. It can be used for checking system pressures, charging refrigerant, evacuating the system, purging non-condensable and adding oil.

The gauge manifold consists of compound and high pressure gauges

mounted on a manifold with hand valves to isolate the common connection or open it to either side as desired.

The left-hand gauge is a compound or suction pressure gauge. The

right- hand gauge is the high or discharge pressure gauge. Flexible hoses are used to make connections from the manifold to the system.

Connecting the gauge manifold to a system is the most common service

function. To avoid introducing contaminants into the system, always purge the hose connections with refrigerant. The service person making the connections should always follow a consistent procedure.

Crack (open slightly) the high-pressure manifold valve, allowing

refrigerant to bleed through the common hose. Allow refrigerant to bleed for a few seconds then close the high-pressure valve on the manifold. Repeat the same procedure with the low-pressure valve. Close the valves on the manifold and crack the low-pressure service valve, connecting the manifold to the system, making it ready for use.

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B. Service Valves Schrader type valves are used on the PCA unit. The Schrader type valve is for convenient checking of system pressures

or charging refrigerant without disturbing the unit’s operation. An adapter is necessary for the standard service gauge or hose connection to fit the Schrader type valve.

The valves are located on the compressor piping leading to each

compressor. Once connections are made, ensure that all service doors are closed as much as possible to allow proper airflow through the condenser coils.

C. Removing Refrigerant Occasionally it will be necessary to remove the refrigerant from a

system. This may be required in order to repair leaks or make other repairs. If a system has been overcharged, it may be necessary to remove the excess charge to insure proper system operation.

EPA Regulations prohibit venting refrigerant into the atmosphere.

Always use a refrigerant recovery system. Check the instructions on the recovery system for proper operation and follow the latest EPA Regulations for refrigerant disposal and records. Check the oil level in the compressor crankcase after the refrigerant is removed.

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D. Adding or Removing Oil

Visually check the oil level in the compressor. The oil level should be visible in or slightly above the center of the sight glass but not below it. Keep in mind that some slight fluctuation in oil level may occur during an operating cycle. As long as the oil level is maintained well within the sight glass, such fluctuations are not harmful. On two compressor sets, one compressor oil level could be below the sight glass when it is first started but should come back after five minutes.

NOTE: If the oil is black in color, call a qualified service technician

because the oil is contaminated and should be replaced. Unless there are particular reasons for changing the oil, do not change it. The oil does not deteriorate or wear out with normal usage.

Excess oil can be removed from the compressors’ crankcase at the Oil

Charging Valve, which is located beneath the oil level of the compressor. To remove oil, connect a manifold hose to the Oil Charging Valve connection, open the manifold valve slowly, and allow the oil to run into a suitable container. Take special care when removing the oil because of oil foaming. The foaming not only may cause the oil to overflow from the container into which it is being drained but also make it difficult to determine the amount of oil being removed.

When sufficient oil has been drained, close the manifold valve tightly

and start the compressor. Allow the compressor to run for approximately one-half hour and then recheck the oil level.

For adding oil: (1) Insert an oil pump into the oil container until it touches the bottom

and push the universal stopper down into the neck opening of the container. (A little oil will keep the stopper from sticking.) The function of the stopper is to stabilize the pump and keep out contamination.

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(2) Connect either copper tube or a manifold charging hose to the 1/4" flare fitting at the top of the pump and attach the other end loosely to the valve on the compressor. Next, purge the air from the hose and tighten the fitting at the system.

(3) When it has been connected and purged, start pumping the oil

into the compressor with slow, even strokes. Always push straight down on the pump.

(4) After pumping the desired charge of oil into the compressor,

remove the connecting hose or tube from the system. Cap the flare connection on the pump to help keep it clean and free of contamination.

E. Dealing with Non-Condensable Gases

A leak in the low-pressure side of an operating system may result in the entrance of air. Before purging non-condensable gases from a system, note the compressor operating discharge pressure and compare it with the temperature of the refrigerant (see Appendix). Since air is non-condensable under the temperatures and pressures encountered in an air conditioning system, the system’s condensing pressure will increase due to the pressures exerted by the trapped air. The amount of increased pressure is dependent on the quantity of air trapped.

If non-condensable gases are suspected in the system, remove the refrigerant charge and evacuate the system to get rid of the non-condensable gases. Once this is completed, recharge the system with the correct amount of refrigerant.

F. Refrigerant Leaks Refrigeration systems must be absolutely air tight for two reasons:

First, any leakage will result in loss of the refrigerant charge. Second, leaks allow air and moisture to enter the system, causing damage to components.

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Leaks can occur not only from joints or fittings, but also from line breakage due to vibration, gasket failure, or other operating malfunctions.

The common means of pressure testing a system for leaks include the

following:

(1) If the system is not already charged with refrigerant, it is more economical and just as effective to slightly charge with refrigerant and then use an inert gas such as dry nitrogen or dry carbon dioxide to build up pressure in the system to approximately 175 psig for testing purposes.

WARNING: NEVER USE OXYGEN FOR PRESSURIZING A

SYSTEM; AN EXPLOSION MAY OCCUR IF OIL IS PRESENT IN THE SYSTEM. ALWAYS USE A GAUGE EQUIPPED PRESSURE REGULATOR ON THE HIGH PRESSURE BACK-UP GAS, AND NEVER INTERCONNECT THE REFRIGERANT CYLINDER AND THE INERT GAS CYLINDER THROUGH A GAUGE MANIFOLD. NITROGEN AND CARBON DIOXIDE CYLINDER PRESSURES CAN RUPTURE A REFRIGERANT CYLINDER.

The electronic leak detector is the most sensitive type available and can detect small leaks of a fraction of an ounce per year, often missed when using other testing methods. Because of their extreme sensitivity, only use electronic detectors in a clean atmosphere not contaminated by refrigerant vapor, smoke, vapor from carbon tetrachloride, or other solvents, which may give a false reaction.

(2) Yet another method is by means of soap bubbles. Swab a

suspected leak with liquid soap or detergent, and bubbles will appear if a leak exists. Despite its simplicity, the soap bubble method can be extremely helpful in pinpointing a leak that is difficult to locate.

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When a leak is located, mark it. When leak testing is completed and all leaks have been located and marked, vent the test pressure gas. If a leak requiring brazing is found in the high-pressure side of a system containing a refrigerant charge in a location that cannot be isolated, remove the refrigerant in order to make repairs.

When pressure has been removed from the area where the leak is

located, repair the leak. It may be necessary to re-braze fittings, replace gaskets, repair flare connections, or merely tighten connections. When all leaks have been repaired, pressurize the system again and repeat the leak testing process.

Pressure leak testing is necessary to locate individual leaks. In order to determine if the system is free of all leaks, a vacuum test is helpful. After repairing all known leaks, draw a deep vacuum on the system with a good vacuum pump. Reduce the pressure to 1 psia or less (the vacuum registered on the test gauge will vary with atmospheric pressure), reseal the system, and leave it for at least 12 hours. Any leakage of air into the system will cause the vacuum reading to decrease. (Changes in ambient temperature may cause some slight change in pressure.) If an air leak is indicated, again pressure leak test the system and locate and repair the leaks.

G. Brazing Refrigerant Lines The refrigeration system must be leak free. Clean and burnish the

tubing bright before brazing. Care in cleaning is essential for good gas-tight connections. Give particular attention to preventing metal particles or abrasive material from entering the tubing.

A suitable low temperature brazing flux that is fully liquid and active

below the flow point of the brazing alloy is required. Brazing fluxes are quite active chemically and must be kept out of the system. Only flux the male connection and use only enough flux to adequately cover the surface.

When heat is applied to copper in the presence of air, copper oxide is

formed. This oxide can be extremely harmful to a refrigerating system. To prevent its formation, sweep an inert gas such as dry nitrogen through the line at low pressure during the brazing operation. Always

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use a pressure-regulating valve in the line connecting the nitrogen cylinder to the system.

Apply heat evenly to the tube and fitting until the flux begins to melt.

The way heat is applied can either draw flux into the joint or prevent its entry. Apply heat around the circumference of the fitting to draw the brazing alloy into the joint, making a mechanically strong and tight joint.

Never apply heat to a line under refrigerant pressure. The line may

rupture, and the escaping refrigerant pressure may throw blazing oil or molten solder through the air. Refrigerants exposed to an open flame may break down into irritating or poisonous gases.

Immediately after the brazing alloy has set, apply a wet brush or cloth to

the joint to wash off the flux. All flux must be removed for inspection and pressure testing.

H. Pressure Testing After repairs are made on a system, refer to sub-section “F” above to

review pressure-testing options. Ensure that no leaks exist before proceeding forward. If leaks are noted, remove pressure from system and re-solder joint(s) per sub-section “G.”

I. Evacuation Any time the compressor or system is exposed to atmospheric air or if

the system becomes contaminated and removal of the refrigerant charge is necessary, evacuate the system. Use a portable vacuum pump specifically built for refrigeration evacuation purposes. The gauge manifold provides a convenient means of connecting the vacuum pump to service valves on the compressor.

Triple evacuation is strongly recommended if possible. To evacuate a

system, attach the common connection on the gauge manifold to the suction connection on the vacuum pump. Connect the “High” and “Low” pressure connections on the gauge manifold securely to the service valves on the “High” and “Low” pressure sides of the system respectively and close the valves on the gauge manifold.

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Start the vacuum pump and gradually open the gauge manifold valves. It may be necessary to restrict the vacuum pump suction pressure by means of the gauge manifold valves to avoid overloading the pump motor. Continue evacuation until the desired vacuum reading on “Low Pressure” gauge is reached.

When evacuation is complete, close the gauge manifold valves tightly,

remove the line from the vacuum pump, and connect it to the refrigerant cylinder. Loosen the common hose connection at the gauge manifold, crack the refrigerant drum valve to purge the hose, and retighten the hose connection. Crack the valves on the gauge manifold until the system pressure rises to 2 psig. Close the refrigerant drum valve and the gauge manifold valves.

For triple evacuation, repeat the above procedure three times,

evacuating twice to 1500 microns and the last time to 500 microns. When the procedure is complete, the system is ready for charging. J. Charging With the gauge manifold connected to the service valves of the system,

connect the common hose to the refrigeration cylinder. Loosen the common hose connection at the gauge manifold, crack the refrigerant drum valve to purge the hose, and retighten the hose connection.

Weigh the refrigerant cylinder prior to charging. Open the refrigerant

cylinder vapor valve, open the suction valve allowing pressure to build up in the system, and start the compressor. Modulate the rate of charging with the gauge manifold valve.

The refrigerant cylinder must remain upright with refrigerant withdrawn

only through the vapor valve to insure that only vapor reaches the compressor. The vaporizing of the liquid refrigerant in the cylinder will chill the liquid remaining and reduce the cylinder’s pressure. To maintain cylinder pressure and expedite charging, warm the cylinder by placing it in warm water or by using a heat lamp. Do not apply heat with a torch.

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To determine if sufficient charge has been introduced, close the refrigerant cylinder valve and observe the system operation. Continue charging until the proper charge has been added. Again weigh the refrigerant drum and subtract the previously determined weight to ensure that only the proper amount of refrigerant has been added.

At times the sight glass may show bubbles or flash gas even when the

system is fully charged. A restriction in the liquid line ahead of the sight glass may cause a sufficient pressure drop to cause flashing of the refrigerant. If the expansion valve feed is erratic or surging, the increased flow when the expansion valve is wide open can create a sufficient pressure drop to create flashing at the receiver outlet. Rapid fluctuations in condensing pressure can also be a source of flashing.

While the sight glass is a valuable aid in determining the proper charge,

the system performance must be carefully analyzed before placing full reliance on it as a positive indicator of the system charge.

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SERVICE Section 4: Introduction to Preventive Maintenance Checklists

March 2013 2-4 Proprietary/Confidential Page 49 © 2013 Twist, Inc

1. Introduction

The following checklists cover all points to be inspected and/or adjusted. A

space is provided for the maintenance person to initial. Twist, Inc. suggests those responsible for unit upkeep make copies of these checklists, give them to the maintenance personnel, and after the service work is completed, bind these checklists into a history of the work performed. The maintenance history must be accessible for review when filing warranty claims.

The checklists are numbered as follows: (1) Quarterly

(2) Semi- Annual (3) Seasonal

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1. Check air filters for cleanliness - clean as instructed in Section 2-9 page 1of this manual.

. Visually check the refrigerant sight glass. Refer to Section 2-3, sub-section “J,” for details.

4. Visually check the oil level in the compressor if a sight glass is available. Refer to Section 2-3, sub-section “D,” for details

5.

Check the color of the indicator element in the center of the refrigerant sight glass. A. GREEN COLOR - The system is dry and is normal. B. CHARTREUSE COLOR - The system has some

moisture and should be watched carefully. Monthly checks should be initiated to look for additional change.

C. YELLOW COLOR - The system contains moisture, and a qualified refrigeration serviceperson must change the drier since the system must be opened to braze in a new dryer and the entire system recharged with refrigerant.

6. Visually check each refrigeration drier for appearance and temperature.

7. Check refrigerant lines and flare nuts. Check lines for wear and leakage and repair accordingly.

8. Visually check air passageways inside the unit for obstruction that may block airflow. Clean accordingly.

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9. Listen for any abnormal noise or vibration. Find the causes and repair the malfunction(s).

10. Check for erratic operation such as the following:

A. Fan cycling - operating on and off quickly – repair if needed.

B. Compressor cycling – operating on and off more than every 3 minutes. Repair if needed.

11. Check supply hoses for holes, tears, abrasion, wear, or leaks. Repair or replace as needed.

12. Check all wire connections for tightness.

13. Check fan hub to motor shaft for tightness. Re-torque hub set screws to motor shaft if necessary.

14. Check general condition of fan blade assembly and replace if necessary.

15. Check all magnetic contactors for abnormal wear. Repair or replace as needed.

16. Confirm proper operations of the VFD.

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SERVICE Section 6: Preventive Maintenance Semi-Annual Checklist

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Perform Semi-Annual Checks in addition to the Quarterly Checks noted in Sections 5.

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1. Check all motors for free rotation and grease all zerk fittings with one-half pump of the grease gun (1/2”). Do not over-lube.

2. Inspect all components in main control panel and repair/replace as necessary.

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2 - 6 March 2013 Page 54

Proprietary/Confidential © 2013 Twist, Inc.


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SERVICE Section 7: Preventative Maintenance Seasonal Checklist

March 2013 2 -7 Proprietary/Confidential Page 55 © 2013 Twist, Inc.

Perform Seasonal Checks in additional to the Quarterly or Semi-Annual checks noted in Sections 5 and 6.

COOLING SEASON CHECKS

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1. Verify that the oil level in the compressors are visible in the sight glass

2. Confirm refrigeration charge levels in all systems.

3. Clean condenser coil. Wash with mild soapy water. Clean more often if environmental conditions dictates.

4. Clean evaporator coil with mild soapy water. Clean more often if environmental conditions dictates.

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Section 8: Adjustments


1. Thermostats

The temperature control for both cooling and heating is automatically

controlled and requires no adjustment. 2. Expansion Valve Superheat Each Thermostatic Expansion Valve is thoroughly tested and set at the factory

before shipment. This factory superheat setting will be correct, and no further adjustment is required for the majority of the applications.

Prior to replacing or repairing the Expansion Valve, turn the valve stem counterclockwise and count the number of turns allowed before a ratcheting sound is heard. Record that number for use later. Once a new valve or valve cartridge is installed, turn the stem counterclockwise until the ratcheting sound is heard. Now turn the stem clockwise the number of turns recorded above. This process will set the new valve to factory specifications. When the adjustment is completed on the valve, always tighten the adjusting stem-packing nut and replace the seal cap tightly.

To determine superheat of the system:

A. Measure the temperature of the suction line at the point the bulb is clamped.

B. Read the gauge pressure at the suction valve near the

compressor. To this pressure add the estimated pressure drop through the suction line between bulb location and compressor suction valve, which is approximately 2 psig. The sum of the gauge reading and the estimated pressure drop will equal the approximate suction line pressure at the bulb.

C. Convert the pressure obtained above to the saturate evaporator

temperature by using the temperature-pressure chart found in the appendix of this manual.

D. Subtract the two temperatures obtained in 1 and 3 - the

difference is superheat. To change the superheat setting:

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Section 8: Adjustments


To reduce the superheat, turn the adjusting stem COUNTER-CLOCKWISE. To increase the superheat, turn the adjusting stem CLOCKWISE. When adjusting the valve, make no more than one half turn of the stem at a time and observe the change in superheat closely to prevent over-shooting the desired setting. As much as 30 minutes may be required for the new balance to take place after an adjustment is made.

The proper superheat setting is between 15°F and 20°F.

3. Hot Gas By Pass Valve Adjustment

This procedure is more easily performed when ambient air temperature is below 85 degrees F.

A. Roll out the aircraft service hose and attach an airflow restriction device

to the aircraft coupler. B. Start the unit and after the unit has run for 20 minutes, restrict the outlet

area of the aircraft coupling. C. All compressor systems should be operating D. To adjust system one, connect the low-pressure gauge of a service

manifold to the Schrader valve on the suction line and read the pressure. Restrict the air flow until the gauge reads 130 psig.

E. Feel the hot gas line downstream of the hot gas valve. It should not be

hot. The valve should start to open at 130 psig. When the valve just starts to open, the line will get cold. Adjust the valve to just open at 130 psig. At 135 psig the valve should be open and the line should be hot.

F. The valve can be adjusted by the spring tension on top of the valve. Adjust the airflow to get the suction pressure higher or lower to test the hot gas valve setting.

G. When service is complete, remove the service gauge manifold

connection and cap the Schrader valves. Replace the cap on the hot gas valve.

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Section 9: Cleaning and Painting


1. Filters The air intake filters are constructed of aluminum mesh media and are the

washable viscous impingement type. To clean the filters, remove each filter from the frame and clean with a vacuum

cleaner or immerse in a warm water and mild detergent mixture. Rinse the filter with a hose and dry with an air hose or air-dry.

2. Condensers When condensers become filled with dust or dirt between the fins, remove the

screen for access. First, remove excess dirt from condensers with soft-bristled paintbrush. Second, use air or water to remove any loosened residue. Apply water or airflow so that residue is directed away from the coil instead of into the coil. In a severe environment, use a non-acid, alkaline based, coil-cleaning solution as described below.

WARNING: WHEN USING AIR (NOT MORE THAN 30 PSIG) FOR

CLEANING, IT IS IMPORTANT TO FOLLOW NORMAL SAFETY PROCEDURES. SERIOUS PERSONAL INJURY CAN RESULT WITH MISDIRECTED PRESSURIZED AIR.

3. Evaporators and Ducts Clean the evaporator coil, plenums, air passages, and ducts using a non-acid,

alkaline based, coil cleaner such as Nu-brite Coil Cleaner. Mix the solution with water as directed by the manufacturer. There are access panels on the plenum to clean the evaporator coil. The other way is to clean it by blowing the solution through the blower and through the coil. To do this, stretch the duct out and secure the end to keep the duct from whipping. Start the unit in vent mode by turning off the compressor and heater circuit breakers. Remove the air filters, and using a fine liquid spray, spray the solution into the air inlet opening. Continue to spray the solution into the opening until the foam leaves the end of the hose. Continue for fifteen minutes or until no dirt comes out of the unit. Spray clean water into the air opening to rinse the solution out of the unit and duct. Continue to operate the unit for another fifteen minutes after the water spray has stopped to dry the unit. Turn unit off and reset the circuit breakers. Clean the air filters and re-install.

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4. Painting A Specifications All aluminum surface preparation and painting of Twist, Inc.’s equipment

is powder coated. All steel services are cleaned, phosphate, primed, and painted with a high zinc content paint.

B Frequency If the paint surface of your PCA unit has been damaged or is showing

signs of rust, immediate repair and/or field touch-up painting is required. It is extremely important that the proper cleaning and painting procedures be followed and that they are performed as soon as possible.

C Materials Before proceeding with repair or maintenance, review product data

sheets and instructions that have been placed on the paint containers covering product warnings and precautions, mixing, application, and curing of all the products specified for use. Verify that all necessary materials are at the job site in acceptable condition and in the correct amounts.

Twist, Inc. recommends that the same materials used for factory

painting be used in field applications. The materials used comprise a two- part epoxy primer and a two-part polyurethane topcoat.

D Ambient Conditions During surface preparation, painting, and curing, protects the surface

from extreme temperatures, moisture, wind-blown sea spray, chemicals, and debris. Do not paint when the surface temperature of the metal is less than 5°F (0.6°C) above the dew point or when the air temperature around the work place is below 55°F (13°C).

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E Surface Preparation NOTE: The success of any paint job depends on the preparation

of the surface being painted. (1) Remove any water-soluble residues and contaminants (mud,

salt, etc.) using a mild detergent followed by a thorough rinsing with clean fresh water.

(2) Remove any water insoluble residues and contaminants (oil,

grease, etc.) by solvent cleaning. F Priming if using an Epoxy based primer Before applying the primer, carefully mix the proper catalyst with the

primer base per the instructions on the paint containers. Priming must be done immediately following the exposure of bare metal in order to prevent additional corrosion. Application may be by brush or spray. Leave the primer to dry at least overnight (12 hours) and no longer than one week before application of the topcoat.

G Finish Coat if using an epoxy based finish coat Before applying the finish coat, carefully mix the proper catalyst with the

finish coat base per the instructions on the paint containers. The final application of the finish coat may be applied with a brush, a paint sprayer, or a roller. Twist, Inc. recommends the topcoat be sprayer applied.

CAUTION: AFTER THE PRIMER OR FINISH COAT IS MIXED, THE

POT LIFE OF THE MIXED PAINT WILL BE LIMITED. CHECK THE INSTRUCTIONS ON THE PAINT CONTAINERS TO DETERMINE THE POT LIFE FOR THE PAINT YOU ARE USING.

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Table of Contents


CHAPTER/ TITLE SECTION PAGE 1: Guide to Repair Introduction ..............................................................................3 – 1 .............. 65 2: Troubleshooting Basic System Trouble I - Unit fails to start ...................................................... 3 - 2............... 67 Trouble II - Excessive power draw ........................................... 3 - 2............... 68 Trouble III - Abnormally low power draw .................................. 3 - 2............... 69 3: Troubleshooting Airflow System Trouble I - Insufficient Airflow ................................................... 3 - 3............... 71 Trouble II - Abnormally noisy blower ........................................ 3 - 3............... 72 4: Troubleshooting Refrigeration System Trouble I - Compressor fails to start ......................................... 3 - 4............... 73 Trouble II - Compressor short cycles or shuts off after a

few minutes of operation ............................................... 3 - 4............... 74 Trouble III - Insufficient cooling ................................................ 3 - 4............... 75 Trouble IV - Excessive compressor vibration ........................... 3 - 4............... 76 Trouble V - Compressor rattles when started ......................... 3 - 4............... 76 Trouble VI - Flutter noise when compressor stops ................... 3 - 4............... 77 Trouble VII - Compressor loses oil/oil in sight glass

below visual level .......................................................... 3 - 4............... 77 Trouble VIII - Evaporator coil(s) freeze up................................ 3 - 4............... 78 Trouble IX - Refrigerant flood back to compressor................... 3 - 4............... 79 Trouble X - Refrigerant suction pressure too high.................... 3 - 4............... 80 Trouble XI - Refrigerant suction pressure too low .................... 3 - 4............... 81 Trouble XII - Refrigerant discharge pressure too high.............. 3 - 4............... 82 Trouble XIII - Refrigerant discharge pressure too low .............. 3 - 4............... 83

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Table of Contents March 2013 Page 64 Proprietary/Confidential © 2013 Twist, Inc.

CHAPTER/ TITLE SECTION PAGE 5: Helpful Troubleshooting Information Shortage of Refrigerant ............................................................ 3 - 5............... 85 Identifying a Refrigerant Leak................................................... 3 - 5............... 85 Air in the Refrigeration System................................................. 3 - 5............... 85 Clogged Filter-Drier .................................................................. 3 - 5............... 86 Dirty Condenser Coil ................................................................ 3 - 5............... 86 Hot Gas By-pass Valve Obstructed.......................................... 3 - 5............... 86 Hot Gas By-pass Valve Adjustment Procedures ...................... 3 - 5............... 87 Expansion Valve Malfunction ................................................... 3 - 5............... 87 Charge Lost ................................................................... 3 - 5............... 87 Valve Stuck in Open Position ........................................ 3 - 5............... 88 Valve Stuck in Closed Position ...................................... 3 - 5............... 88 Bulb Miss-located .......................................................... 3 - 5............... 88 Moisture in Valve ........................................................... 3 - 5............... 88 Expansion Valve Field Disassembly/Re-assembly................... 3 - 5............... 89 Power Element Replacement ........................................ 3 - 5............... 90 Compressor Electrical Phase Rotation..................................... 3 - 5............... 90 Compressor Operating in a Vacuum ........................................ 3 - 5............... 91 Fusite Failures ............................................................... 3 - 5............... 91 Scroll Galling ................................................................. 3 - 5............... 91 Compressor Motor Megging..................................................... 3 - 5............... 92 Overcharge of Refrigerant........................................................ 3 - 5............... 92 6. Troubleshooting Direct Digital Controller (DDC) Determine if ALC is Operating Property ................................... 3 - 6............... 93 Checking Controller Inputs ....................................................... 3 - 6............... 95 Checking Controller Output ...................................................... 3 - 6............... 95 Thermal Overloads................................................................... 3 - 6............... 95 Control Voltage......................................................................... 3 - 6............... 96 Smoke Detector ....................................................................... 3 - 6............... 96 Phase Monitor .......................................................................... 3 - 6............... 96 Heating Coils ........................................................................... 3 - 6............... 96 Cooling Compressors............................................................... 3 - 6 .............. 96

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Section 1: Guide to Repair


1. Introduction This chapter is to guide service personnel when the Pre-Conditioned Air unit

needs repair. The tables in this section outline the problems, likely causes, and remedies. As it is impossible to foresee all breakdowns, this chapter should not be expected to provide answers to every failure.

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Section 2: Troubleshooting Basic System


Trouble I: Unit fails to start

PROBABLE CAUSE SUGGESTED REMEDY 1. Power Failure 1. Check for power at the main breaker for

the PCA unit. 2. Main disconnect switch or

breaker supplying power to PCA unit open or tripped

1. Determine cause if tripped. Make repairs as necessary and turn switch or circuit breaker back on.

3. Branch circuit breaker tripped 1. Check circuit and determine if component(s) have shorted to ground.

4. Control system circuit breakers tripped

1. Check system for grounds. Make necessary repairs and reset circuit breaker

1. Check pushbutton circuit with meter to verify if a ground exists. Make repairs or replace as necessary and test the system.

2. Confirm if applicable switch is functioning properly.

5. Remote pushbutton switch malfunctioning

3. Check to see if moisture has gotten into the switch box

6. Blower motor VFD fails to energize motor

1. Check control circuit to verify that power is available at the VFD contacts.

2. If power is available at the load side of the VFD, verify status of motor windings.

1. Check for proper phase relationship and ensure that all three phases have voltage.

2. Check for proper voltages. The unit will stop if the voltage is too high or too low.

7. Phase Monitor does not indicate “ON” in display window and unit does not start

3. Check for balance voltage on all three legs. The phase monitor will stop the unit if the voltage is not balanced within 8%.

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Trouble II: Excessive power draw

PROBABLE CAUSE SUGGESTED REMEDY 1. Coils are plugged up. Clear obstruction

in front of condenser coils 2. System is over-charged. 3. Liquid line filter plugged. 4. Expansion Valve failed.

1. High head pressures in compressor

5. Compressor is mechanically damaged internally. Vibration and discolored oil could accompany this symptom.

1. Connect supply duct to an aircraft. 2. Blower motor drawing excessive current due to operation of the unit while it is not connected to an aircraft.

2. If in a test mode, partially block the aircraft connector or kink hose to simulate aircraft resistance.

3. Unit operating at low voltage 1. Stop operations and correct voltage at source.

4. Single phasing of motors due to loss of one phase in the power supply or mechanical connection of the wiring

1. Repair connections at all connection points include locations such as magnetic contactors.

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Trouble III: Abnormally low power draw PROBABLE CAUSE SUGGESTED REMEDY 1. Incorrect compressor electrical

phasing 1. Compressor must be re-phased to run in

the correct direction. Changing two-phase wires in the compressor junction box can do this. NOTE: If the compressor is phased improperly, the following will occur: a. Compressor draws low amperage. b. Suction and discharge pressures

change very little. c. Rattling or rumbling sound may be

apparent. d. Compressor vibrates excessively.

2. Compressor mechanically damaged internally

1. Replace compressor.

1. Check for proper airflow on supply side of unit.

3. Low load on the refrigeration system

2. Check ambient air temperature to verify if unit is operating in proper range.

4. Excessive voltage 1. Check power source.

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Section 3: Troubleshooting Airflow System


Trouble I: Insufficient airflow

PROBABLE CAUSE SUGGESTED REMEDY

1. Blower wheel loose on motor shaft 1. Repair connection.

1. Check operation of VFD. 2. VFD not running at the right speed.

2. Check electrical connection on VFD.

1. Straighten duct to aircraft.

2. Check aircraft connector for obstructions and remove any restrictions.

3. Flexible duct to aircraft is kinked, is obstructed, or leaks

3. Repair leaks.

4. Air filters dirty or obstructed 1. Clean air filters per instructions in Chapter 2-9 page 1 of this manual.

5. Evaporator coil frosted or iced-up 1. See “Evaporator Coil(s) Freeze Up” Chapter 3-5 page 6.

6. Leaking unit-to-duct and/or duct-to-aircraft connections

1. Check duct connections for loose or poor-fitting joints and tighten or repair as necessary.

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Section 3: Troubleshooting Airflow System


Trouble IIU: Abnormally noisy blower


1. Blower motor bearings are worn 1. Repair or replace motor and blower motor contactor.

2. Blower wheel out of balance 1. Remove wheel, and balance or replace it as required.

3. Blower wheel loose on shaft 1. Adjust and retighten blower wheel as necessary.

4. Blower wheel hitting or rubbing inlet cone

1. Readjust blower inlet cone or wheel on shaft.

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Section 4: Troubleshooting Refrigeration System


Trouble I: Compressor fails to start


1. Burned out motor in compressor or open motor winding

1. Replace compressor.

1. See Section 3-2 Trouble #2.

2. Compressor motor overheated due to low refrigerant charge. Find leak, repair, and charge with refrigerant.

3. Compressor phased incorrectly causing motor to overheat. Correct phasing of power to compressor.

2. Internal thermal switch

4. Compressor rapidly cycles, causing motor to overheat. Correct cycling malfunction.

1. Check for loose connections in circuit.

2. Check magnetic contractor to ensure that all phases exist on both line and load sides.

3. Manual Motor Starter tripped

3. Check compressor to ensure that motor is not grounded to casing.

1. Check overload setting.

2. Verify that magnetic contact is in good working order and that all phases of power exist at both line and load sides.

4. Compressor overload tripped

3. Check compressor to ensure that motor is not grounded to casing.

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Trouble I: Compressor fails to start (continued)


1. Check for sufficient refrigeration charge in system.

5. Suction pressure below cut-out setting of low pressure switch

2. Check system for refrigeration leaks.

1. Reset pressure switch.

2. Check refrigeration system for proper charge.

6. Discharge pressure above cut-out setting of high pressure switch

3. Check condenser airflow.

7. Excessively low voltage 1. Correct at power source.

8. Controller not operating properly 1. Check controller for proper operations and replace if necessary.

Trouble II: Compressor short cycles or shuts off after a few minutes of operation


1. Intermittent connections in electrical system

1. Check for loose connections in the electrical system. Tighten all connections.

2. Evaporator coil frosted or frozen, causing low suction pressure

1. See “Evaporator Coil(s) Freeze Up” Chapter 3-5 page 6.

3. Excessive head pressure, causing high pressure switch to open

1. See “Refrigerant Discharge Pressure too High” Chapter 3-5 page 10.

4. Faulty compressor motor 1. Replace compressor.

5. Low supply airflow 1. Check for kinks in the duct and clean air filters. See Section 3-3 Trouble #1 for additional information.

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Trouble III: Insufficient cooling


1. Shortage of refrigerant 1. Verify refrigerant charge. Add refrigerant as necessary. (See Chapter 3-6 page 1.)

2. Clogged filter-drier 1. Check by touch if in-and-out temperature difference can be sensed. Replace as necessary. (See Chapter 3-6 page 2.)

3. Expansion valve clogged or mechanically malfunctioning

1. Repair or replace assembly. (See Chapter 3-6 page 4.)

4. Obstructed air to the condenser coils

1. Clean coils.

5. Air or other non-condensable gases in the system

1. Check and purge system and/or replace refrigerant charge as necessary. (See Chapter 3-6 page 1.)

6. Excessive refrigerant charge 1. Reclaim excess refrigerant from system. (See Chapter 3-6 page 9.)

7. Evaporator coil frosted or frozen, causing low suction pressure

1. Evaporator coil(s) freeze up. (See Chapter 3-5 page 6.)

8. Improper superheat adjustment 1. Check superheat and reset thermostatic expansion valve. (See Chapter 2-8 page 1.)

9. Evaporator Pressure Regulator out of adjustment

1. Adjusted as directed in Chapter 3-6 page 3.

10. Compressor malfunctioning 1. Replace compressor. 11. Overcharge of refrigerant or non-

condensable gas in system, causing high discharge pressures

1. Reclaim refrigerant, remove non-condensable gas from refrigerant, and re-install refrigeration in system. Verify system operations.

12. Controller not operating properly 1. Check temperature settings on device and correct or replace component as necessary.

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Trouble IV: Excessive compressor vibration


1. Compressor loose on mounting 1. Tighten attaching parts as required.

2. Lack of oil 1. Check oil level and add oil as necessary. The compressor will likely need to be replaced.

3. Compressor internally damaged 1. Replace compressor.

4. Liquid "flood back" caused by expansion valve being out of adjustment, loose sensing bulb, or broken capillary tube.

1. Retighten sensing bulb, readjust expansion valve as necessary or replace power element. (See Chapter 3-6 page 6.)

Trouble V: Compressor rattles when started


1. Compressor electrically out of phase rotation. The compressor will be noisy and vibrate excessively. The oil sump will become warm when running backwards.

1. Correct phase rotation to A-B-C.

NOTE: (Start-up) Under conditions of low refrigerant flows (low suction pressure) such as at start up, a rattling sound may emanate from the compressor. This is most likely to be heard under such conditions of low ambient starts where it takes time to build sufficient head pressure, allowing the thermal expansion valve to flow refrigerant and increasing the suction pressure. This sound should diminish and disappear as the suction pressure increases.

NOTE: (Flooding) If a compressor should experience severe refrigerant flooding, it will make a loud "rattling" sound. This is normal because the separation of the scrolls allows the liquid refrigerant to pass through the compressor without damage.

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Trouble VI: Flutter noise when compressor stops


1. The scroll compressor has special characteristics that make it unlike a reciprocating compressor; therefore, flutter noise at shut down is normal.

1. Normal condition.

NOTE: At shutdown, the gas within the scrolls expands and causes momentary reverse rotation until the discharge check valve seats. This results in a "flutter" type noise.

Trouble VII: Compressor loses oil/oil in sight glass below visual level

PROBABLE CAUSE SUGGESTED REMEDY 1. Insufficient oil charge. Oil level too

low 1. Run unit under maximum load for at

least 30 minutes and check oil level to ensure that oil returns to compressor. Once again check level and if necessary, add oil accordingly.

2. Clogged drier or expansion valve 1. Replace drier (See Chapter 3-6 page 2.)

3. Crankcase oil valve leaks oil (oil around compressor base and low crankcase oil level)

1. Repair/replace valve, confirm oil leak has stopped, and add proper refrigerant oil as necessary.

4. Excessive liquid refrigerant returning to compressor

1. See Trouble IX. Chapter 3-5 page 7.

5. Refrigerant leak (loosing both oil and refrigerant)

1. Repair leaking system and re-charge. (See Chapter 3-6 page 1.)

6. Oil trapped in system 1. Operate unit at maximum load for at least 30 minutes and re-check level.

7. Loose expansion valve remote bulb 1. Provide good contact between remote bulb and suction line. (See Chapter 3-6 page 4.)

8. Liquid flooding back to compressor 1. Readjust superheat setting or check remote bulb contact. (See Chapter 2-8 page 1.)

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Trouble VIII: Evaporator coil(s) freeze up


1. Blower wheel loose on motor shaft 1. Repair hub connection.

1. Check operation of VFD and associated connections and repair or replace as necessary.

2. VFD not running at the right speed.

2. Check voltage going to VFD.

1. Straighten duct to aircraft.

2. Check aircraft connector for obstructions and remove restriction.

3. Flexible duct to aircraft kinked, obstructed, or leaks

3. Repair leaks in gaskets and hoses.

4. Air filters dirty or obstructed 1. Clean air filters per instructions in Chapter 2-9 page 1 of this manual.

5. Leaking unit-to-duct and/or duct-to-aircraft connections

1. Check duct connections for loose or poor fitting joints and tighten or repair as necessary.

6. Suction pressure too low 1. See Trouble XI Chapter 3-5 page 9 of this manual. Also refer to Chapter 2 Section 2-8 for EPR Valve information.

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Trouble IX: Refrigerant flood back to compressor


1. Water or a mixture of water and oil frozen in expansion valve

1. Reclaim refrigeration. Thoroughly evacuate system and replace filter drier.

2. Expansion valve seat leaks 1. Replace valve or effected parts as needed. (See Chapter 3-6 page 4.)

3. Incorrect expansion valve bulb location

1. Install bulb on suction line at 45° up from bottom, ensure good surface-to-surface contact, and ensure that bulb is insulated from outside influence. (See Chapter 3-6 page 4.)

4. Low superheat adjustment on expansion valve

1. See Chapter 2-8 page 1 of this manual.

5. Restricted or plugged Expansion Valve equalizer line

1. Reclaim system, repair/replace equalizer line, and re-charge.

6. Low supply airflow 1. See Trouble II Chapter 3-3 page 1 of this manual.

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Trouble X: Refrigerant suction pressure too high

PROBABLE CAUSE SUGGESTED REMEDY 1. Ambient temperature above design

conditions 1. Condition could be normal. Allow

unit to operate at higher supply air temperatures.

2. Excessive airflow caused by no restriction on discharge hose

1. Attach duct to aircraft, or for testing, obstruct aircraft adapter to simulate aircraft resistance.

3. Overfeeding of expansion valve 1. Adjust superheat setting of expansion valve and check to see that remote bulb is properly attached to suction line. (See Chapter 2-8 page 1 and Chapter 3-6 page 4.)

4. Expansion valve stuck open position 1. Repair or replace valve. (See Chapter 3-6 page 4.)

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Trouble XIU: Refrigerant suction pressure too low


1. Lack of refrigerant 1. Check system for charge level and leaks. Repair and re-charge. (See Chapter 3-6 page 1.)

2. Ambient temperature below design conditions

1. Do not operate unit.

3. Clogged or dirty filter drier 1. Check by touch if “in” an “out” temperature differences can be sensed; replace drier. (See Chapter 3-6 page 2.)

4. Expansion valve power assembly has lost charge

1. Reclaim refrigeration system. Replace expansion valve power assembly and re-charge system. (See Chapter 3-6 page 4.)

1. Check operation of damper motor and associated connections. Repair or replace as necessary.

2. Check voltage to damper motor.

5. Damper motor not operating damper

3. Check for obstructions in operation.

6. Obstructed expansion valve 1. Reclaim refrigeration charge, repair or replace valve, and re-charge system. (See Chapter 3-6 page 4.)

7. Compressor internal suction screen is plugged

1. Check by measuring the crankcase pressure at the oil charging valve and comparing it to the pressure upstream of the compressor. If pressures are the same, the valve is OK, and the crankcase pressure is lower, the screen is plugged. Replace compressor.

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Trouble XIIU: Refrigerant discharge pressure too high


1. Obstructed air to the condenser coils 1. Clean coils.

2. Air or other non-condensable gases in the system

1. Reclaim refrigerant, check system for leaks, remove non-condensable from gas, and re-charge system.

3. Excessive refrigerant charge 1. Reclaim system and re-install proper amount of refrigerant.

1. Check circuit breakers, overloads, and magnetic contactors. Repair/replace components as necessary.

2. Check control circuit to ensure that control power is available.

3. Check fan cycling switch to ensure status of voltage and condition of switch.

4. Check fan blade assembly for proper mounting. Retighten hub onto shaft if necessary.

4. Condenser fan not operating

5. Repair/replace fan motor as necessary.

5. Ambient temperature above design condition

1. Unit will automatically shut-down compressor. High Pressure Switch is a automatic reset switch.

6. Restriction in discharge line to condenser

1. Reclaim refrigerant and remove restriction in line. Re-charge system and test.

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Trouble XIII: Refrigerant discharge pressure too low


1. Lack of refrigerant 1. Reclaim system and check for leaks. Re-charge system and test.

2. Compressor malfunction 1. Replace compressor.

3. Ambient temperature too low 1. Do not operate unit.

4. Compressor operating backward 1. Change phase rotation to ABC. (See Chapter 3-6 page 7.)

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Section 5: Helpful Troubleshooting information


1. Shortage of Refrigerant There should always be sufficient liquid in the condenser to completely fill the

liquid line. If there is a shortage of refrigerant, a mixture of gas and liquid will pass into the expansion valve. Bubbles will appear in the sight glass: the larger the bubbles the more severe the refrigerant shortage. Frequently there will be a hissing or whistle at the expansion valve. The coil and suction line will be relatively warm while the suction pressure will be low due to little or no liquid being supplied to the evaporator.

2. Identifying a Refrigerant Leak

Leaks may occur from line breakage due to vibration or other operating

malfunctions. Use an electronic leak detector, if available, since it is the most effective form

of detection. The simplest and oldest method of leak detection is by means of soap bubbles. Swab a suspected leak with liquid soap or detergent, and bubbles will appear if a leak exists. Despite its simplicity, the soap bubble method can be extremely helpful in pinpointing a leak that is difficult to locate. This method will not pinpoint a very small leak.

3. Air in the Refrigeration System If air or other non-condensable gases are present in the system, they will tend

to move toward and collect at the condenser. The head pressure will rise to a point above the pressure corresponding to the temperature at which the vapor is condensing. In extreme cases, the pressure may rise to a point where either the high-pressure cutout or the overload in the starter may stop the compressor.

To determine whether or not there is air in the system, allow the compressor to

stand idle long enough for the entire system to cool down to the temperature of the surrounding air. After the system has reached the same temperature as the surrounding air, the reading of the head pressure gauge should not be more than 10 lb. above the saturation pressure corresponding to the surrounding air temperature. See the Appendix for R-407C pressure/temperature relationship.

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4. Clogged Filter-Drier Occasionally the filter-drier in the liquid line may become clogged with dirt or

other foreign material left in the system during assembly or servicing. When this happens, the liquid leaving the filter-drier will feel cooler than the liquid entering. If it is badly clogged, some sweat or frost may appear at the filter-drier outlet.

If the drier is frosted or if there is a perceptible temperature change between the liquid line entering and leaving the drier, an excessive pressure drop in the drier is indicated, and the drier should be replaced.

5. Dirty Condenser Coil When condensers become filled with dust or dirt between the fins, remove the

louvers for access. First, remove excess dirt from condensers with soft-bristled paintbrush. Second, use air or water to remove any loosened residue. Apply water or airflow so that residue is directed away from the coil instead of into the coil. In a severe environment, use a non-acid, alkaline based, coil cleaning solution as described below.

UWARNINGU: THEN USING AIR (NOT MORE THAN 30 PSIG) FOR

CLEANING, IT IS VERY IMPORTANT TO FOLLOW NORMAL SAFETY PROCEDURES, OR SERIOUS PERSONAL INJURY CAN RESULT.

6. Hot gas By-pass Valve Obstructed

The hot gas by-pass valve in the downstream refrigeration systems maintains a minimum evaporator coil temperature by controlling the suction pressure to the evaporator coil. If the valve is clogged or inoperative, no control is maintained. Check if the solenoid valve upstream of the valve is opened. The solenoid valve is controlled by the ALC output.

7. Hot Gas By-pass Valve Adjustment Procedure

This procedure is more easily performed when ambient air temperature is below 85 degrees F.

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A. Roll out the aircraft service hose and attach an airflow restriction device to the aircraft coupler.

B. Start the unit and after the outlet damper is fully open, restrict the outlet

area of the aircraft coupling to 25 percent. C. Cause all compressor systems to operate. E. Connect the low-pressure gauge of a service manifold to the Schrader

valve on the suction line and read the pressure. Restrict the air flow until the gauge reads 50 psia.

E. Feel the hot gas line downstream of the hot gas valve. It should be hot.

The valve should start to open at 52 psia.

G. The valve can be adjusted by the spring tension on top of the valve. Adjust the airflow to get the suction pressure higher or lower to test the hot gas valve setting.

G. Remove the service gauge manifold connection and cap the Schrader valves. Return the unit to service.

8. Expansion Valve Malfunction A. Charge Lost The power element of an expansion valve consists of the remote bulb,

capillary tube, and the bellows or diaphragm which actuates the valve cage. If this power element is inoperative or has lost its charge, the valve will either maintain an almost closed position or may close completely. To test for an inoperative power element:

(1) Stop compressor. (2) Remove remote bulb from contact with suction line. (3) Place bulb in ice water. (4) Start compressor. (5) Remove bulb from ice water and warm in hand. At the same

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time check the evaporator outlet line for a rapid temperature change, this indicates flood through of liquid refrigerant. If refrigerant floods through the valve, the power assembly operates properly.

UWARNINGU: DO NOT FLOOD BACK THROUGH SUCTION LINE FOR

AN EXTENDED PERIOD SINCE EXCESSIVE LIQUID FLOOD BACK MAY DAMAGE THE COMPRESSOR.

B. Valve Stuck in Open Position If the expansion valve is stuck in an open position, there will be an

excessive amount of sweating on the suction line and compressor crankcase due to the large amount of liquid being passed into the suction line. In units with sight glass in the compressor crankcase, excessive foaming will be seen.

C. Valve Stuck in Closed Position A warm supply air temperature may indicate an expansion valve that is

stuck. When this happens, the suction pressure will be low. D. Bulb Miss-Located Clamp the expansion valve bulb to the horizontal suction line near the

evaporator outlet. Clean the suction line thoroughly before clamping the remote bulb in place. Install the remote bulb at the position of about 4 or 8 o'clock. After clamping it to the line, thoroughly insulate it with material that will not absorb moisture.

E. Moisture in Valve Water or a mixture of water and oil frozen in the valve port or working

parts of the valve will prevent proper operation. This is a common source of trouble on expansion valves. Since the

valve is the first cold spot in the system, moisture will freeze and block the valve open, closed, or in any position in between. (See “B” and “C” above.)

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9. Expansion Valve Field Disassembly/Reassemble

A. Before disassembling the valve, recover refrigerant and be sure the

pressures in the system, both high and low side, have been reduced to a safe level (0 psig).

B. Remove the seal cap and turn the adjustment stem counter-clockwise

until a ratcheting sound is noted. This will relieve the spring force. Count and record the number of turns, so adjustment can be returned to its original position.

C. Using appropriate wrenches to properly support the valve body, remove

the power element, the bottom cap assembly, and the internal parts. D. Replace any items that appear damaged. Follow the instructions in the

valve repair/replacement kit and be sure the push rod length is correct. E. Clean all parts with oil-free solvent, preferably by applying and then

blowing it off with clean, dry compressed air. F. To re-assemble valves, screw seat into body. Use hand pressure only

since it does not require a heavy torque on this small knife-edge joint. UCAUTION:U BE SURE HEXAGON CORNERS OF SEAT DO NOT

PROTRUDE INTO PUSHROD HOLES. G. Slip the pin and carrier (which have been pressed together at the

factory) into the body. Before tapping these parts together, check the concentricity of both the pin and seat by engaging the parts and noting that there is no tendency to stick together. Lightly tap the pin into the seat to create a true seating surface. Repeat this several times, rotating the pin carrier a quarter of a turn each time.

H. Place the spring guide stamping and spring in the pin carrier. Place the

lower spring guide on the opposite end of the spring and screw the bottom cap in place. After screwing bottom cap assembly in place, carefully tighten, preferably with two 10" adjustable wrenches, to seal the metal-to-metal knife-edge joint. The sealing surfaces should be free of any foreign material or nicks that might prevent a leak-tight joint.

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I. Check the height of the pushrod above the element-sealing surface with the pushrod gauge. The gauge is supplied with internal parts kits or can be obtained at no-charge upon request from Sporlan Valve Co.

UCAUTION:U IF THE ELEMENT-TO-BODY JOINT UTILIZES A

GASKET, REMOVE THE GASKET BEFORE CHECKING PUSHROD HEIGHT. IF THE PUSHROD(S) ARE TOO LONG, CAREFULLY GRIND THEM OFF TO THE PROPER LENGTH. CLEAN THE PUSHROD(S) OF ALL DIRT AND GRINDINGS AND PLACE THEM INTO THE BODY.

J. Power Element Replacement - If the element is damaged or has lost its

charge, replace it as follows: Always use an appropriate wrench on the wrench flats provided. DO

NOT use a wrench on the outer welded edge of the element. The sealing surfaces should be free of any foreign materials or nicks that might prevent a leak-tight joint. A few drops of refrigerant oil on the element threads will facilitate easy assembling and removal.

K. Return the superheat adjustment stem to its original position. This can

be done by turning the stem counter-clockwise until a ratcheting sound is heard then clockwise the number of turns recorded prior to disassembly.

L. Replace the seal cap tightly.

10. Compressor Electrical Phase Rotation For the compressor to operate properly, it must be phased for proper rotation.

The proper phasing is T1-Phase A, T2-Phase B, and T3-Phase C. To change the rotation, swap any two phase wire at the compressor terminal block.

The compressor rotation can be checked two ways. The first is to use a phase

meter that will indicate proper phasing of A-B-C. The second method is to start the compressor and watch the suction and discharge pressures. The suction pressure should drop, and the discharge pressure should rise. If the compressor is phased incorrectly, it will exhibit the following symptoms:

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A. Low current draw - you can expect about half of the normal operating amperage.

B. Suction and discharge pressures will change very little and will be about

equal.

C. After a long running time (up to 30 minutes of running backwards) the motor winding thermostat opens due to excessive heat.

D. Compressor makes a lot of noise. E. Compressor vibrates.

UWARNINGU: RUNNING THE COMPRESSOR BACKWARDS WILL

DAMAGE THE COMPRESSOR IF RUN FOR AN EXTENDED PERIOD OF TIME. ALWAYS ENSURE THAT THE COMPRESSOR IS RUNNING PROPERLY AFTER MAKING REPAIRS OR REPLACEMENTS.

11. Compressor Operating in a Vacuum UCAUTION:U OPERATING THE SCROLL COMPRESSOR IN A

VACUUM WILL RESULT IN ELECTRICAL OR MECHANICAL DAMAGE TO THE COMPRESSOR.

The scroll compressor can pull into a vacuum much quicker than a

reciprocating compressor. There are two failures that will occur due to running the compressor in a vacuum:

A. Fusite failures - The fusite terminals will arc internally which results in a

motor failure. B. Scroll galling – This occurs due to no or a very low flow of refrigerant.

This is most likely to occur if the compressor is run into a vacuum. It happens because there is no flow, and the discharge temperature is in the range of 400-500°F, which causes the orbiting scroll to rub on the fixed scroll, resulting in a compressor failure. The failure will start to initiate in 1-2 minutes of operation and will only deteriorate further after the failure starts.

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UNOTE:U Reciprocating compressors are often pumped into a vacuum to check if the valves are defective. Since the scroll compressor does not have valves, there is no need to apply this test to a scroll compressor.

12. Compressor Motor MeggingU UCAUTION:U DO NOT UNDER ANY CIRCUMSTANCES USE A MEGOHM

METER OR APPLY POWER TO THE WINDINGS OF A COMPRESSOR WHILE IT IS IN A VACUUM. MOTOR WINDINGS DAMAGE WILL RESULT.

Typical acceptable megohm readings considered safe to start a compressor

should not be less than 1,000 ohms per volt of the nominal motor voltage. Example: 380 volt compressor - 380,000 ohms 460 volt compressor - 460,000 ohms Generally, a 500 volt DC megohm insulation tester is recommended for

testing the compressor motor windings. The use of a megger with a voltage of more than 500 volts is not recommended for insulation systems of 600 volts or less because of the potential for damage to the insulation system.

If readings below these values are measured, evacuate the compressor to

insure complete dehydration, bring it back up to a positive pressure with refrigerant and remeg. It may be necessary to clean the terminal plate before re-megging.

UWARNINGU: SINCE THE MOTOR ACTS LIKE A CAPACITOR WHEN

VOLTAGE IS APPLIED, GROUND THE MOTOR WINDING TERMINAL STUDS TO THE MOTOR FRAME AFTER COMPLETING TEST. THIS WILL DECREASE ANY RESIDUAL VOLTAGE IN THE MOTOR THAT COULD RESULT IN A SEVERE ELECTRICAL SHOCK.

13. Overcharge of Refrigerant An overcharge of refrigerant will cause high condensing pressure. Liquid will

back-up in the condenser and decrease the amount of surface available for condensing. As a result, the condensing pressure will rise. In extreme cases, it may rise to a point where the high-pressure cutout will stop the compressor.

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Section 6: Troubleshooting Direct Digital Controller (DDC)


Troubleshooting the ALC is divided into three tasks. First, check the operation of the ALC itself to ensure proper operation. Next, check the inputs to be sure they are responding correctly. Lastly, test the outputs to be sure all wiring and safety devices are in proper order. 1. Determining if ALC is Operating Properly

Check to be sure that 24 VAC power is applied properly. This can be determined this quite easily by looking at the ALC in the control panel. If any LED’s are lit or blinking, the ALC is receiving power. If the power condition is still in question, check that the power switch is in the ON position then check the power connection of the ALC from the terminal labeled 24VAC to Gnd using a digital multi meter (DMM). This is the AC power supply for the ALC and should be within 10% of 24 VAC. If proper voltage is applied but the above conditions do not occur either the software is not loaded correctly, or the ALC is possibly defective. A red LED labeled POWER on the right hand side of the ALC will show whenever power is being provided to the ALC. NOTE: The I/O Flex 6126 is protected by internal solid state Polyswitches on

the incoming power and the network connections. These Polyswitches are not replaceable and will reset themselves if the condition that caused the fault returns to normal.

There is a run LED and error LED. These LED indicates the condition of the module. Run LED Error LED Condition 2 flashes / second Off Normal 2 flashes / second 2 flashes alternating Five minute auto delay after system error. 2 flashes / second 2 flashes in sync, Module is configured for a then pause. different baud rate than the rest of the network segment. 2 flashes / second 3 flashes, then off Module has been formatted

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2 flashes / second 4 flashes then pause Two or more devices on this

Network have the same ARC156 network address.

2 flashes / second On Exec halted after frequent system errors or GFBs halted. 5 flashes / second On Exec start-up aborted, Boot is running. 5 flashes / second Off Firmware transfer in progress, Boot is running. 7 flashes / second 7 flashes / second Ten second recovery alternating period after brownout. 14 flashes / second 14 flashes / second, Brownout

Alternating

There are other LEDs that provide information of the condition of the unit. Digital Output Status Lights when the digital output is activated. Analog Output Status Lights when the analog output is activated. Rx Lights when the module receives data from the network segment, there is an Rx LED for ports 1 and 2a. Tx Lights when the module transmits data over the network segment, there is a Tx LED for Ports 1 and 2a. There are two push buttons available for this unit. One is for Regional Jet mode, and the other is for Narrow Body mode. Depending on which pushbutton is depressed the ALC will bring the unit up in the proper mode, determining by ambient temperature the correct running mode for the present conditions.

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Push the “Start” button and confirm that the start control relay inside the control panel close and latch – if not, check the wiring sequence for the pushbuttons. During this sequence, the VFD should start the blower. The control mode relay will latch and no other motor starters will close until the ALC gets a signal from the VFD that it is running. Push the “Stop” button after these checks are performed.

The ALC program requires that all of the temperature probes be present and operating correctly before the program will run. If the red LED labeled FAULT turns on, this indicates a fault condition in the ALC program. If this LED is “On” and the unit will not start, go to the section “Checking Controller Inputs”, below.

2. Checking Controller Inputs Each temperature probe is connected to two terminals on the analog input terminal block. Check the wiring to be sure it is correct.

The input point for the Current Transducer (CT) is a 4 to 20 milliamp input When the “Start” mode relay is closed, the ALC should begin to start the unit by signaling the VFD to start the blower. If the start mode relay is closed and the unit does not start the circuit may not be correct. The other input points are digital inputs. If the switch is closed, there should be continuity at the terminal block it is connected to. If the input point is active, the input LED should light.

3. Checking Controller Output Output points can be checked using the computer. It is possible that the outputs have wiring problems, blown fuses, or possibly bad relay contacts or coils. If the ALC LED display is indicating that an output point is on but the physical device is not responding, check the circuit wiring, circuit breakers and thermal overloads.

4. Thermal Overloads

The next most likely cause of a problem is that the thermal overloads are tripped. Reset the overloads and check the system again. If the overloads trip on a regular basis, check the amperage of the motor. Check the settings of

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the overload. They should be set at the motor running amps. 5. Control Voltage

Four control transformers are used; one 480VAC to 120VAC transformer, one 120 VAC to 24 VAC transformer to run the main control system, and two120VAC to 24 VAC transformer, one for the controller, and one for the hot gas bypass valve. The ALC and the hot gas valve requires a floating 24VAC source. 120 VAC is also necessary to power the condensate pump. The pump runs when necessary and is controlled by a float switches to remove condensate water. Check for 120 VAC on the top of transformer TR-2.

6. Smoke Detector

If the smoke detector trips the 24 VAC control power is interrupted. The ALC

controller will seem to operate normally, but the blower will not start. Also note that the red fault light on the control panel will turn on and will not clear when the stop button is depressed. To clear the fault, turn the power off for 10 seconds and then on, or push the reset button on the smoke detector.

7. Phase Monitor If the phase monitors trips, the 24 volt control power is interrupted. This allows

the ALC controller to remain in operation but disables all discrete output points. The red fault light will turn on. Reset the phase monitor and restore proper power to the PC Air unit, if necessary, and depress the stop/reset button to return to normal operation.

8. Heating Coils

The heating coils have two additional safeties built in to protect their operation. If the ALC controller is calling for heat but the coils don’t seem to operate, check the low airflow limit switch and the high temperature limit switches.

9. Cooling Compressors

Each cooling compressor has three additional safeties built in to protect its

operation. If the ALC controller is calling for cooling but the compressors don’t seem to operate, check the high and low refrigerant pressure limit switches and the high compressor temperature limit switch.

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Table of Contents


CHAPTER/ TITLE SECTION PAGE 1. Major Repair Removal for Major Repair ........................................................ 4 - 1............... 99 Removal for Overhaul .............................................................. 4 - 1............... 99 Replacement Parts................................................................... 4 - 1............... 99 2. Shipping Procedures Shipping Procedure..................................................................4 – 2 ............ 101 6. Storage Procedures

Storage Procedure ................................................................... 4 - 3............. 103

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Table of Contents

Table of Contents March 2013 Page 98 Proprietary/Confidential © 2013 Twist, Inc.


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Section 1: Major Repair

March 2013 4 -1 Proprietary/Confidential Page 99 © 2013 Twist, Inc.

1. Removal for Major Components

If the repair is of such a magnitude that removal is necessary, remove the component through the side panels directly in front of the component.

UNOTE:U Bottom panels as well as panels on the sides are readily removable

for complete access and serviceability.

2. Removal for Overhaul

No major overhaul should be attempted on any individual component. If the component is not covered in this manual, the component should be removed and returned to the manufacturer or other authorized facility for replacement.

3. Replacement Parts The following list of parts is reprehensive of items used in this unit. If any one item needs replacement, the list will guide the user to procure

the right parts. These parts are available through: Twist, Inc. 47 South Limestone Jamestown, OH 45335 Phone 937-675-9581 Fax 937-675-3766 Consumable Products

Description Manufacture Refrigerant DuPont

Refrigerant Oil BVC32 Polyvinylether

Coil Cleaner Nu-Brite

Starter Duct 20’ Section Twist

Flat Duct 20’ Section Twist

Reducer 14” to 8” Flat Twist

Aircraft Adapter Twist

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Section 1: Major Repair

4 -1 March 2013 Page 100 Proprietary/Confidential © 2032 Twist, Inc.

Part No.

Qty Used

Description

Vender

SDR3X-5/8-10-S 1 Valve ,Electric Hot Gas Bypass, 5/8 Sporlan

IB-3 1 Interface Board, SDR-3, SDR-3x Sporlan

OZE-25,1-1/8 x 1-3/8 1 Valve, Expansion 25 Ton Sporlan

OZE-35,1-1/8 x 1-3/8 1 Valve, Expansion 35 Ton Sporlan

SA-19S 2 Sight Glass 1 1/8 ODF Sporlan

C-609-S 2 Filter Drier 1 18 ODF Sporlan

E14S270-HP 1 Valve, Solenoid 7/8 - 24 VAC Sporlan

MKC-2-24 1 Coil, Solenoid Valve 24 VAC Sporlan

GSD80385VAB42 1 Compressor, Scroll 32 Ton 410A Bitzer

GSD80182VAB42 2 Compressor, Scroll 15 Ton 410A Bitzer

343256-03 2 Crankcase Heaters 150W Bitzer

347027-14 2 Motor Portection Modules, 24 VAC Bitzer

PC9013 4 Transducer, Pressure, 0-750 PSIG IFM Efector

A/CP-1-10-NW-BB 2 Temperature Sensor, 10” 4888”Di h

AGI

D4120 1 Smoke Detector System Sensor 316-02-22A30AC**1 2 Filter, 22 X 30 x 2 Alum. AAFG FD63B225L 1 CB, Main 225 Amps. Thermo Mag Siemens

S17FD60 1 CB, shunt trip, 24VAC Siemens

MBS63EH-630-G 1 CB Contactor Starter, 63 Amps, 3P EE Controls

CB4A2PD 1 Circuit Breaker, 4 Amps, 2P EE Controls

JJS-80A 3 Fuse 80A for VFD T-Tron

CMR001 7 Fuse 1 A Bussman 300-S09N30XC10,24V 2 Contactor, 9 Amps, 24 VAC C3 Controls

330-T25S2U10 2 CB MS 6.3-10 Amp. C3 Controls

1DM401 1 Switch, Door Interlock Micro Switch

ACS550-U1-059A-4+BO55 1 VFD, Blower 40HP, 480VAC,3PH ABB

I/O FLEX 6126 1 Controller, Flex I/O6126 ALC

I/O FLEX 8160 1 Expansion Board Flex I/O8160 ALC

GPRM-B4C05C-3 7 Relay, 4PDT, 5A, 24 VAC, LED,STOP C3 Controls

3UG4513-1BR20 1 Relay, 3PH Line Monitoring 400VAC Siemens

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Documents

Property of American Airlines Maintenance · A. Cleanliness of the refrigeration system Absolute cleanliness is necessary in a refrigeration system in order to insure reliable and