Application Guidelines - Danfossfiles.danfoss.com/technicalinfo/dila/17/FRCC.PC.019.A2.22-VRJ-Nov... · Application Guidelines ... Essential piping design considerations ... electronic

Danfoss Inverter scroll compressor, VRJFor Residential Applications - R410A

Application Guidelines

http://danfoss.us.com/


4 FRCC.PC.019.A2.22

Contents

Introduction ...............................................................................................6Scroll compressor components ................................................................................................................................. 6Compressor size .............................................................................................................................................................. 6Performance ..................................................................................................................................................................... 6

Compressor model designation ...............................................................7Nomenclature .................................................................................................................................................................. 7Label .................................................................................................................................................................................... 7Serial number ................................................................................................................................................................... 7

Technical specifications ............................................................................8Compressor specifications .......................................................................................................................................... 8Performance data .......................................................................................................................................................... 8Variable speed drive specifications .......................................................................................................................... 8Bearings lubrication ....................................................................................................................................................... 8

Dimensions ................................................................................................9VRJ 028 - 035 - 044.......................................................................................................................................................... 9

Electrical data, connections and wiring ..................................................10Supply Voltage ...............................................................................................................................................................10Compressor electrical specifications ......................................................................................................................10LRA (Locked Rotor Amp) .............................................................................................................................................10MCC (Maximum Continuous Current) ....................................................................................................................10Winding resistance ........................................................................................................................................................10Wiring connections ......................................................................................................................................................11Terminal cover mounting ...........................................................................................................................................11Terminal cover removal ...............................................................................................................................................11IP rating .............................................................................................................................................................................11Internal motor protection ...........................................................................................................................................11Phase sequence and reverse rotation protection ..............................................................................................11

Approvals and certificates .......................................................................12Approval and certificates ............................................................................................................................................12Pressure equipment directive 97/23/EC ...............................................................................................................12Low voltage directive 73/23/EC, 93/68/EC ...........................................................................................................12Internal free volume .....................................................................................................................................................12

Operating conditions ...............................................................................13Refrigerant and lubricants ..........................................................................................................................................13Motor supply ...................................................................................................................................................................13Compressor ambient temperature ..........................................................................................................................13


5FRCC.PC.019.A2.22

Contents

Application envelope ...................................................................................................................................................14High and low pressure protection ...........................................................................................................................15Crankcase heating .........................................................................................................................................................15Oil return management ...............................................................................................................................................15On/off cycling (cycle rate limit) .................................................................................................................................16Start-up sequence .........................................................................................................................................................16

System design recommendations ..........................................................17General ..............................................................................................................................................................................17Essential piping design considerations .................................................................................................................17Refrigerant charge limit ..............................................................................................................................................18Reversible heat pump systems .................................................................................................................................18Minimum sump superheat .........................................................................................................................................18Preventing liquid flood back ....................................................................................................................................18Water utilising systems ...............................................................................................................................................19Loss of charge protection ...........................................................................................................................................19Oil level checking and top-up ...................................................................................................................................19

Sound and vibration management .........................................................20Starting sound level ......................................................................................................................................................20Running sound level .....................................................................................................................................................20Stopping sound level ...................................................................................................................................................20Sound generation in a refrigeration system and air conditioning system ...............................................20

Installation ................................................................................................22System cleanliness.........................................................................................................................................................22Compressor handling and storage ..........................................................................................................................22Compressor mounting .................................................................................................................................................22Compressor holding charge ......................................................................................................................................22Tube brazing procedure ..............................................................................................................................................22Brazing material .............................................................................................................................................................22Compressor connection ..............................................................................................................................................23Vacuum evacuation and moisture removal .........................................................................................................23Liquid line filter driers ..................................................................................................................................................24Refrigerant charging .....................................................................................................................................................24Insulation resistance and dielectric strength ......................................................................................................24Compressor replacement after motor burn out .................................................................................................24

Ordering information and packaging ....................................................25Packaging ........................................................................................................................................................................25Ordering code numbers ..............................................................................................................................................25


6 FRCC.PC.019.A2.22

Introduction

Scroll compressor components

Compressor size

Performance

Danfoss VRJ for residential applications developed by Danfoss is a complete package consisting of a dedicated variable speed compressor, variable speed drive, application controller, electronic expansion valve (EEV), EEV controller and sensors. Three nominal system

sizes are available (3, 4 and 5 TR), based on three compressor models.

These Selection & Application Guidelines focus on the variable speed scroll compressor.

The motor stator is rigidly attached to the shell. The rotor is shrink-fit onto the eccentric shaft. The shaft is supported by two bearings, one in the crankcase and the second below the motor.

Variable speed technology offers more flexibility in compressor selection than fixed speed compressors. Selection of the right variable speed compressor size can be done by different methods:

• Maximum cooling capacity: select a compressor size that achieves the peak load system cooling capacity demand at its maximum speed.

• Nominal cooling capacity: select a compressor size that achieves the nominal system cooling capacity at a rotational speed of 3000-4200 rpm (50-70Hz).

• Best Seasonal Efficiency Ratio: select a compressor size that achieves the minimum

system cooling demand at its minimum speed. Ensure that the compressor is able to cover the peak load system cooling capacity. This selection makes the compressor to run for a maximum of time at part load where the system efficiency is highest.

Danfoss scroll compressors are manufactured using the most advanced machining, assembly, and process control techniques. In design of both the compressor and the factory, very high standards of reliability and process control were first priority. The result is a highly efficient product with the highest reliability obtainable, and a low sound level.

The Danfoss VRJ compressors referenced in this guide is a fully compliant scroll and actually improves with run time in its early commissioning.

A seventy-two hour run-in is recommended to meet performance expectations.


7FRCC.PC.019.A2.22

Compressor model designation

Label

Serial number

KS 123450903

Production year

Production week

Manufacturing location Incremental number

Application, Family& refrigerant V: Variable speed R: Residential J: R410A, PVE lubricant

Swept VolumeDisplacement in cc/rev

Model VariationU: Design optimised for high SEER

Other features6: No other features

Equipment versionP: Brased connections, spade terminals

Motor protectionN: No internal motor protection (protection by drive)

VoltageK: 420V DCL IPM

U

Model Variation

028

Swept Volume

VRJ

Application, Family

& Refrigerant

K

Voltage

N

Motor Protection

P

EquipmentVersion

6

Other FeaturesNomenclature


8 FRCC.PC.019.A2.22

Technical specifications

Performance data

Variable speed drive specifications

Bearings lubrication

Compressor

model

Swept volume Displacement Oil charge Net weight

cu.in/revMin speed 30 Hz 60 Hz Max speed

oz lb900 rpm 1800 rpm 3600 rpm 4200 rpm

VRJ028 1.64 51 103 206 240 36 68VRJ035 2.12 66 133 265 310 45 71VRJ044 2.65 83 166 332 387 45 71

Compressor specifications

For dedicated variable speed drive specifications, refer to “Danfoss VRJ Installation and Operation instructions”.

A specific oil pump ensures optimal bearing lubrication at all compressor speeds. This to have sufficient bearing lubrication at low speeds as well

as avoid excessive Oil Circulation Ratio (OCR) at high speeds.

Conditions Compressor model

Nominal Tons

Compressor speed Compressor capacity Compressor isentropic efficiencyrpm Hz Btu/hr Ton

High SEER conditions

(H)

VRJ028 3 Tons3600 60 36700 3.06 66.24200 70 42700 3.56 64.9

VRJ035 4 Tons 3600 60 46400 3.87 67.64200 70 53400 4.45 65.1

VRJ044 5 Tons3600 60 57800 4.82 68.34200 70 68100 5.68 67.0

CHEER conditions

VRJ028 3 Tons3600 60 36500 3.04 65.94200 70 42300 3.53 64.3

VRJ035 4 Tons3600 60 46200 3.85 67.34200 70 53000 4.42 64.6

VRJ044 5 Tons3600 60 57900 4.83 68.84200 70 68300 5.69 67.5

Heat Pump conditions

VRJ028 3 Tons3600 60 25100 2.09 59.74200 70 29300 2.44 58.8

VRJ035 4 Tons3600 60 31800 2.65 61.04200 70 36700 3.06 59.0

VRJ044 5 Tons3600 60 40200 3.35 62.24200 70 47300 3.94 61.2

SEER conditions (I)

VRJ028 3 Tons 1800 30 21000 1.75 68.5

VRJ035 4 Tons 1800 30 26800 2.23 69.7

VRJ044 5 Tons 1800 30 34500 2.88 70.9

Conditions Evaporating Temperature

(°F)

Condensing Temperature

(°F)

Superheat (°F)

Subcooling(°F)

High SEER conditions (H) 50 115 20 15

CHEER conditions 45 100 20 15

Heat Pump conditions 30 110 20 15

SEER conditions (I) 55 100 20 15


9FRCC.PC.019.A2.22

Dimensions

VRJ 028 - 035 - 044

Mounting grommet

0.067

1.614

Ø 1.614

1.161

5/16” - 18 UNCself tapping

Recommended torque for mounting bolts:8 ft.lbs (±1ft.lbs)

Ø 0.433

9.40

4 x Ø 0.75 - 0.783.750

5.06

4.38

2.74 - 2.8034° 31°

45°

14°

4.323.750

7.491 - 7.509

9.40

7.491 - 7.509

15.53

Suction port 3/4” ODF

6.438 - 6.515

2.84 - 2.95

14.19

7.76 9.09

0.42

0.75

Discharge port 1/2” ODF

All dimensions in inch


10 FRCC.PC.019.A2.22

Electrical data, connections and wiring

Supply Voltage VRJ compressors must not be connected directly to the mains supply. They must only be powered through the dedicated Danfoss variable speed drive.

Compressor model Variable Speed Drive ModelVRJ028 176L7000VRJ035 176L7001VRJ044 176L7002

Nominal voltage 208-230V – 1Ph – 60HzVoltage range 187 – 253 V

Refer to “Danfoss VRJ Installation and Operation instructions” for more details about supply voltage.

Compressor electrical specifications

Compressor model LRA MCC Winding resistanceA A Ohm

VRJ028 10.2 18 0.255VRJ035 12 23.5 0.210VRJ044 12 30 0.210

LRA (Locked Rotor Amp)

MCC (Maximum Continuous Current)

Winding resistance

LRA is the higher average current as measured on a mechanically blocked compressor tested under nominal voltage. LRA is printed on the nameplate, according to UL requirements. With

VRJ compressors, the LRA value is low because the variable speed drive reacts very rapidly (far below 1 second).

The MCC value is the maximum at which the compressor can be operated in transient conditions and out of the operating envelope. The

MCC value is measured based on UL conditions (max load) and at low voltage.

VRJ scroll compressors are equipped with an IPM (permanent magnet) motor.

Winding resistance is the resistance between indicated terminal pins at 77°F (resistance value ± 7%).

Winding resistance is generally low and it requires adapted tools for precise measurement. Use a digital ohm-meter, a ‘4 wires’ method and measure under stabilised ambient temperature. Winding resistance varies strongly with winding

temperature ; If the compressor is stabilised at a different value than 77°F, the measured resistance must be corrected with following formula:

Rtamb= R77°F

a + t amb

a + t77°F

t77°F: reference temperature = 77°F

t amb : temperature during measurement (°F)

R77°F : winding resistance at 77°F

Rtamb : winding resistance at tamb

a: Coefficient a= 390


11FRCC.PC.019.A2.22

Electrical data, connections and wiring

Terminal cover mounting The terminal cover and gasket should be installed prior to operation of the compressor. The terminal cover has two outside tabs, 180 degrees apart, that

engage the terminal fence. When installing the cover, check that it is not pinching the lead wires.

Terminal cover removal

Internal motor protection

Phase sequence and reverse rotation protection

IP rating

Wiring connections

VRJ scroll compressors are not equipped with an internal motor protector. Motor protection is provided by the variable speed drive. All

motor para-meters are factory preset in order to guaranty optimal locked rotor or overload current protection.

The compressor will only operate properly in a single direction. If electrical connections are done correctly between the drive and the compressor terminals (compressor and drive terminals T1, T2 and T3 matching), the drive will provide correct phase supply to the compressor, and reverse rotation will be not possible.

If compressor and drive T1, T2 and T3 terminals are not matching, the compressor can go in reverse rotation. This results in excessive noise, no pressure differential between suction and discharge, and suction line warming rather than immediate cooling. The compressor can be rapidly severely damaged in these conditions.

The compressor terminal box IP rating according to CEI 529 is IP22 for all models. This IP rating is only valid when correctly sized cable glands with the same IP rating are applied.

• First numeral, level of protection against contact and foreign objects 2 protection against object size over 1/2 inch (fingers of similar)

• Second numeral, level of protection against water 2 protection against dripping water when tilted up to 15°

VRJ scroll compressors will only compress gas while rotating counter-clockwise (when viewed from the compressor top).

The drawing shows electrical terminal labelling and should be used as a reference when wiring the compressor.

T1, T2 and T3 of the drive and the compressor must be connected accordingly. Refer to “Danfoss VRJ Installation and Operation instructions” for details and cable sizes.

Quick connect spade terminalsP terminal box type

push

push

push


12 FRCC.PC.019.A2.22

Approvals and certificates

Approval and certificates VRJ scroll compressors comply with the following approvals and certificates.

Pressure equipment directive 97/23/EC

Low voltage directive 73/23/EC, 93/68/EC

Internal free volume

Manufacturer's declaration of incorporation ref. EC Machines Directives 98/392/CE Contact Danfoss

Products Internal free volume at LP side without oil (in.3)

VRJ028 - 035 - 044 179

Refrigerating fluids Group 2Category PED IEvaluation module no scope

UL (Underwriters Laboratories) All models

Other approvals / certificates Contact Danfoss


13FRCC.PC.019.A2.22

Operating conditions

Refrigerant and lubricants

Motor supply

Compressor ambient temperature

General information

High ambient temperature

PVE

Low ambient temperature

Residual moisture

When choosing a refrigerant, different aspects must be taken into consideration:• Legislation (now and in the future)• Safety• Application envelope in relation to expected

running conditions• Compressor capacity and efficiency• Compressor manufacturer

recommendations & guidelines

Additional points could influence the final choice:• Environmental considerations• Standardisation of refrigerants and

lubricants• Refrigerant cost• Refrigerant availability

In case of enclosed fitting and high ambient temperature, it is recommend to check the

temperature of power wires and conformity to their insulation specification.

Polyvinyl ether (PVE) is an innovative refrigeration lubricant for HFC refrigerant systems. PVE is as hygroscopic as existing polyolester lubricants (POE), but PVE does not chemically react with water; no acids are formed and compressor evacuation is easier.

The compressor technology applied in Danfoss VRJ scroll compressors in combination with PVE lubricant provides the best possible result in terms of reliability and compressor lifetime.

Although the compressor itself can withstand low ambient temperature, the system may require specific design features to ensure safe

and reliable operation. See below sections for recommendations.

Prior to shipment from the factory, every compressor is dehydrated, evacuated, and charged with dry nitrogen. Maximum residual

moisture levels are 0.0082 oz. for model VRJ028, and 0.0120 oz. for VRJ035 and VRJ044.

VRJ scroll compressors can be operated only connected to the dedicated variable speed drive, at nominal voltages as indicated in “supply

voltage” section. Under-voltage and over-voltage operation is allowed within the indicated voltage range.

VRJ scroll compressors can be applied from -13°F to 125°F ambient temperature. The compressors are designed as 100 % suction gas

cooled without need for additional fan cooling. Ambient temperature has very little effect on the compressor performance

VRJ scroll compressor application range is influenced by several parameters which need to be monitored for a safe and reliable operation.

These parameters and the main recommendations for good practice and safety devices are explained hereunder:

Refrigerant and lubricants Motor supply Compressor ambient temperature Application envelope (evaporating temperature, condensing temperature, return gas temperature)


14 FRCC.PC.019.A2.22


The operating envelope for VRJ scroll compressors is given in the figure below, where the condensing and evaporating temperatures represent the range for steady-state operation. Under transient conditions, such as start-up and defrost for heat pump applications, the compressor may operate outside this envelope for short periods.The operating limits serve to define the envelope within which reliable operations of the compressor are guaranteed:

• Maximum discharge gas temperature: +275°F• Suction superheat is dedictated by the

minimum sump superheat (see graph p16).• Maximum superheat of 40°F• Minimum and maximum evaporating

and condensing temperatures, as per the operating envelopes.

All the below limits, temperatures and speeds, are secured by the parameters in the drive and application controller software’s.

The discharge temperature depends mainly on the combination of evaporating temperature, condensing temperature and suction gas superheat and speed. Discharge gas temperature should be controlled with an insulated sensor attached to the discharge line, 6 in. from the compressor shell. Maximum discharge gas temperature must not exceed 275°F when the compressor is running within the approved operating envelope.

Refer to “Danfoss VRJ Installation and Operation instructions” for connection details, and to “Sensor Selection Guideline” manual for selection details and technical brochures about temperature sensors.

Application envelope

Maximum discharge gas temperature

35

45

55

65

75

85

95

105

115

125

135

145

155

900 - 4500 RPM

2100 - 3750 RPM2200 - 3300 RPM2300 - 2850 RPM

2400 RPM Derated

1100 - 4500 RPM

1300 - 4500 RPM

1500 - 4200 RPM

1800 - 4200 RPM

-40 -30 -20 -10 0 10 20 30 40 50 60 70 80Saturated evaporating temp. (°F)

Satu

rate

d co

nden

sing

tem

p. (°

F)

2610141822263034384246505458626670

-40 -36 -32 -28 -24 -20 -16 -12 -8 -4 0 4 8 12 16 20 24

(°C)

(°C

)


15FRCC.PC.019.A2.22


Pressure settings

High pressure

Low pressure

High pressure ratio

Crankcase heating

Oil return management

R410AWorking pressure range high side psig 119 - 645Working pressure range low side psig 28 - 202Maximum high pressure safety switch setting psig 653Minimum low pressure safety switch setting psig 22

: LP safety switch shall never be bypassed

According to UL requirements, a high pressure safety switch is still mandatory in any system, even with high pressure transmitters connected and used via the variable speed drive.

HP switch settings shall not exceed the maximum service pressure of any system components. The high-pressure switch can be set to lower values

depending on the application and ambient conditions. The HP switch must either be placed in a lockout circuit or consist of a manual reset device to prevent cycling around the high-pressure limit. If a discharge valve is used, the HP switch must be connected to the service valve gauge port, which must not be isolated.

A low pressure (LP) safety switch is recommended. Deep vacuum operations of a scroll compressor can cause internal electrical arcing and scroll instability. Danfoss scroll compressors exhibit high volumetric efficiency and may draw very low vacuum levels, which could induce such a problem. The minimum

low-pressure safety switch (loss of charge safety switch) setting is given in the above table. Either the LP safety switch must be a manual lockout device or an automatic switch wired into an electrical lockout circuit. The LP switch tolerance must not allow for vacuum operations of the compressor.

Scroll compressors are machines with fixed volume ratio, and operate more efficiently near the design pressure ratio. In the extreme, do not exceed a 7.5:1 pressure ratio (absolute discharge pressure to absolute suction pressure)

for extended periods. The Danfoss VRJ scroll compressor is equipped with an internal pressure relief valve for protection against blocked condenser and fan failure conditions.

A crankcase heating function can be provided by injecting a DC current in the motor of the compressor, to keep the compressor warm, and avoid liquid migration during off cycle.

Refer to “Danfoss VRJ Installation and Operation instructions” for details.

A specific function can be enabled to secure the oil return to the compressor. When the compressor is running at minimum speed for

extended periods, every half hour, speed will be increased to 2400 rpm for a 80 seconds period.

Suction and discharge pressure transmitters have to be installed and connected to the variable speed drive to ensure the compressor operates within the application envelope described above.

Refer to “Danfoss VRJ Installation and Operation instructions” for connection details, and to “Sensor Selection Guideline” manual for selection details and technical brochures about pressure transmitters.

High and low pressure protection


16 FRCC.PC.019.A2.22


Start-up sequence To ensure correct lubrication of all the mechanical parts, VRJ compressors start with a defined ramp-up, and stay at a fixed speed

for some seconds. Then the compressor speed increases up to the desired set point according to capacity request.

On/off cycling (cycle rate limit)

The on/off cycling protection is included in the variable speed drive. There is no need for extra on/off cycling protection.


17FRCC.PC.019.A2.22

System design recommendations

Proper piping practices should be employed to ensure adequate oil return, even under minimum load conditions with special consideration given to the size and slope of the tubing coming from the evaporator. Tubing returns from the evaporator should be designed so as not to trap oil and to prevent oil and refrigerant migration back to the compressor during off-cycles.

It is particularly important and critical with variable capacity systems, where very low velocities can be achieved for long periods of time, generating oil return issues.

If the evaporator lies above the compressor, as is often the case in split or remote condenser systems, the addition of a pump-down cycle is strongly recommended. If a pump-down cycle were to be omitted, the suction line must have a loop at the evaporator outlet to prevent refrigerant from draining into the compressor during off-cycles.

If the evaporator were situated below the compressor, the suction riser must be trapped so as to prevent liquid refrigerant from collecting at the thermal bulb location (see fig. 1).

When the condenser is mounted at a higher position than the compressor, a suitably sized «U»-shaped trap close to the compressor is necessary to prevent oil leaving the compressor from draining back to the discharge side of the compressor during off cycle. The upper loop also helps avoid condensed liquid refrigerant from draining back to the compressor when stopped (see fig. 2). The maximum elevation difference between the indoor and outdoor section cannot exceed 26 feet. System manufacturers should specify precautions for any applications that exceed these limits to ensure compressor reliability.

Piping should be designed with adequate three-dimensional flexibility. It should not be in contact with the surrounding structure, unless a proper tubing mount has been installed. This protection proves necessary to avoid excess vibration, which can ultimately result in connection or tube failure due to fatigue or wear from abrasion. Aside from tubing and connection damage, excess vibration may be transmitted to the surrounding structure and generate an unacceptable noise level within that structure as well (for more information on noise and vibration, see the section on: “Sound and vibration management” section.

Essential piping design considerations

Successful application of scroll compressors is dependent on careful selection of the compressor for the application. If the compressor is not correct for the system, it will operate

beyond the limits given in this manual. Poor performance, reduced reliability, or both may result.

General

0.5 % slope,13 ft/s or more

0.5 % slope,13 ft/s or more

U-trap

U-trap, as short as possible

U-trap, as short as possible

max. 13 ft

�g.1

max. 13 ft

26 to 40 ft/s

To condenser

Evaporator

Condenser

HP

U-trap

3D flexibility

Upper loop

LP

fig. 2


18 FRCC.PC.019.A2.22


Reversible heat pump systems

Minimum sump superheat

Preventing liquid flood back

Transients are likely to occur in reversible heat pump systems, i.e. a changeover cycle from cooling to heating, defrost or low-load short cycles. These transient modes of operation may lead to liquid refrigerant carryover (or flood back) or excessively wet refrigerant return conditions. As such, reversible cycle applications

require specific precautions for ensuring a long compressor life and satisfactory operating characteristics. Specific tests for repetitive flood back are required to confirm whether or not special system design considerations should be considered.

The minimum sump temperature is in the range from 10°F to 30°F above saturated suction

temperature. Refer to the flood back test criteria.

Danfoss recommends the use of an electronic expansion valve for all air conditioning and heat pump applications with VRJ compressors. An EXV has two key benefits: it provides modulating control of the system under varying load conditions, and it protects the compressors from flood back during adverse running conditions.

Exceptions to the use of EXV’s with Danfoss VRJ must be approved by Danfoss application engineering.

Scroll compressors can tolerate liquid refrigerant up to a certain extend without major problems. However, excessive liquid refrigerant in the compressor is always unfavourable for service life. Besides, the installation cooling capacity may be reduced because of the evaporation taking place in the compressor and/or the suction line

instead of the evaporator. System design must be such that the amount of liquid refrigerant in the compressor is limited. In this respect, follow the guidelines given in the section: “Essential piping design recommendations” in priority.

Refrigerant charge limit

0

5

10

15

20

25

30

35

40

-10 0 10 20 30 40 50 55

Acceptable

Unacceptable

Floodback requirement

Sum

p su

perh

eat,

°F

Saturated suction temp. °F


19FRCC.PC.019.A2.22


Oil level checking and top-up

Loss of charge protection

In installations with good oil return and line runs up to 50 ft, no additional oil is required. If installation lines exceed 50 ft, additional oil may be needed. 1 or 2% of the total system refrigerant charge (in weight) can be used to roughly define the required oil top-up quantity.

Always use oil from new cans.

Top-up the oil while the compressor is idle. Use any accessible connector on the compressor suction line and a suitable pump.

VRJ scroll compressors together with the variable speed drive include a loss of charge protection function. This protection is ensured if pressure

and temperature sensors are connected to the drive.

Water utilising systems Apart from residual moisture in the system after commissioning, water could also enter the refrigeration circuit during operation. Water in the system shall always be avoided. Not only because it can shortly lead to electrical failure, sludge in sump and corrosion but in particular because it can cause serious safety risks.

Common causes for water leaks are corrosion and freezing.

Corrosion: Materials in the system shall be compliant with water and protected against corrosion.

Freezing: When water freezes into ice its volume expands which can damage heat exchanger walls and cause leaks. During off periods water inside heat exchangers could start freezing when ambient temperature is lower than 32°F. During on periods ice banking could occur when the circuit is running continuously at too low load. Both situations should be avoided by connecting a pressure and thermostat switch in the safety line.


20 FRCC.PC.019.A2.22

Sound and vibration management

Running sound level

Stopping sound level

Sound generation in a refrigeration system and air conditioning system

Compressor sound radiation

During start-up transients, it is natural for the compressor sound level to be slightly higher than during normal running. Danfoss scroll

compressors exhibit very little increased start-up transient sound.

VRJ scroll compressors are designed with optimised discharge ports and wrap geometry

to reduce the sound level when a compressor is running.

VRJ scroll compressors have very low shutdown sound due to minimal volume of discharge volume to push scrolls in reverse at shutdown.

Due to this small re-expansion, there is no internal break mechanism required to prevent reverse spin of the scroll set.

Typical sound and vibration in refrigeration and air conditioning systems encountered by design and service engineers may be broken down into the following three source categories.Sound radiation: This generally takes an airborne path.Mechanical vibrations: These generally extend

along the parts of the unit and structure.Gas pulsation: This tends to travel through the cooling medium, i.e. the refrigerant.The following sections will focus on the causes and methods of mitigation for each of the above sources.

For sound radiating from the compressor, the emission path is airborne and the sound waves are travelling directly from the machine in all directions.

The VRJ scroll compressor is designed to be quiet and the frequency of the sound generated is pushed into the higher ranges, which not only are easier to reduce but also do not generate the penetrating power of lower-frequency sound.

Use of sound-insulation materials on the inside of unit panels is an effective means of substantially

reducing the sound being transmitted to the outside. Ensure that no components capable of transmitting sound/vibration within the unit come into direct contact with any non-insulated parts on the walls of the unit.

Because of the Danfoss unique design of a full-suction gas & oil cooled motor, compressor body insulation across its entire operating range is possible.

Starting sound level

Sound level vs Speed

56

58

60

62

64

66

68

70

72

74

76

78

45/1304200

45/1303600

45/1003600

45/1002400

45/1001800

45/100900

Condition (Tsat(suction) / Tsat (discharge) and speed (RPM)

Soun

d po

wer

leve

l (dB

A)


21FRCC.PC.019.A2.22

Sound and vibration management

Speed bypass

Gas pulsation

Mechanical vibrations

If vibrations still occur at some typical frequencies, a speed bypass function is available within the VRJ. This function allows avoiding

some frequency ranges and avoiding vibrations to occur. Refer to “Danfoss VRJ Installation and Operation instructions” for setting details.

The VRJ scroll compressor has been designed and tested to ensure that gas pulsation has been optimised for the most commonly encountered air conditioning pressure ratio. On heat pump installations and other installations where the pressure ratio lies beyond the typical range, testing should be conducted under all expected

conditions and operating configurations to ensure that minimum gas pulsation is present. If an unacceptable level is identified, a discharge muffler with the appropriate resonant volume and mass should be installed. This information can be obtained from the component manufacturer.

Vibration isolation constitutes the primary method for controlling structural vibration. VRJ scroll compressors are designed to produce minimal vibration during operations. The use of rubber isolators on the compressor base plate is very effective in reducing vibration being transmitted from the compressor to the unit. Rubber grommets are supplied with all Danfoss compressors. Once the supplied rubber grommets have been properly mounted, vibrations transmitted from the compressor base plate to the unit are held to a strict minimum. In addition, it is extremely important that the frame supporting the mounted compressor be of sufficient mass and stiffness to help dampen any residual vibration potentially transmitted to the frame. The tubing should be designed so as

to both reduce the transmission of vibrations to other structures and withstand vibration without incurring any damage. Tubing should also be designed for three-dimensional flexibility.

During unit development, the complete compressor speed range should be covered, in order to define if abnormal vibrations occur or not. As ultimate solution, speed bypass can be applied.

For more information on piping design, please see the section entitled “Essential piping design considerations”.


22 FRCC.PC.019.A2.22

Installation

System cleanliness

Compressor handling and storage

Compressor mounting

Compressor holding charge

Tube brazing procedure

Brazing material

Each VRJ scroll compressor is shipped with printed Instructions for installation.

The refrigerant compression system, regardless of the type of compressor used, will only provide high efficiency and good reliability, along with a long operating life, if the system contains solely the refrigerant and oil it was designed for. Any other substances within the system will not improve performance and, in most cases, will be highly detrimental to system operations.

The presence of non-condensable substances and system contaminants, such as metal shavings, solder and flux, has a negative impact on compressor service life. Many of these contaminants are small enough to pass through a mesh screen and can cause considerable damage within a bearing assembly. The use of highly hygroscopic PVE oils in R410A compressors requires that the oil be exposed to the atmosphere just as little as possible.

System contamination is one of main factors affecting equipment reliability and compressor service life. It is important therefore to take system cleanliness into account when assembling a refrigeration system.

During the manufacturing process, circuit contamination may be caused by:• Brazing and welding oxides,• Filings and particles from the removal of

burrs in pipe-work,• Brazing flux,• Moisture and air.Consequently, when building equipment and assemblies, the following precautions must be taken: never drill holes into the pipe-work after installation.

Compressors are provided with a lifting lug. This lug should always be used to lift the compressor. Once the compressor is installed, the lifting lug should never be used to lift the complete installation. The compressor must be handled

with caution in the vertical position, with a maximum inclination of 15° from vertical. Store the compressor between -30°F and 120°F, not exposed to rain or corrosive atmosphere.

Maximum inclination from the vertical plane, while operating must not exceed 7 degrees. All compressors are delivered with 4 rubber

grommets and metal sleeves. Compressors must always be mounted with these grommets.

Each compressor is shipped with a nominal dry nitrogen holding charge between 6 psi and 10 psi, and is sealed with elastomeric plugs. The plugs should be removed with care to avoid oil loss when the holding charge is released. Remove the suction plug first and the discharge plug

afterwards. The plugs shall be removed only just before connecting the compressor to the installation in order to avoid moisture entering the compressor. When the plugs are removed, it is essential to keep the compressor in an upright position to avoid oil spillage.

Do not bend the compressor discharge or suction lines or force system piping into the compressor connections, because this will increase

stresses that are a potential cause of failure. Recommended brazing procedures and material, are described on following page.

For copper suction and discharge fittings, use copper-phosphorus brazing material. Sil-Fos® and other silver brazing materials are also acceptable.

If flux is required for the brazing operation, use coated rod or flux core wire. To avoid system contamination, do not brush flux on.


23FRCC.PC.019.A2.22

Installation

Vacuum evacuation and moisture removal

When brazing the compressor fittings, do not overheat the compressor shell, which could severely damage certain internal components due to excessive heating. Use of a heat shield and/or a heat-absorbent compound is highly recommended. For brazing the suction and discharge connections, the following procedure is advised:

• Make sure that no electrical wiring is connected to the compressor.

• Protect the terminal box and compressor painted surfaces from torch heat damage (see diagram).

• Use only clean refrigeration-grade copper tubing and clean all connections.

• Purge nitrogen or CO2 through the compressor in order to prevent against oxidation and flammable conditions. The compressor should not be exposed to the open air for extended periods.

• Use of a double-tipped torch is recommended.

• Apply heat evenly to area A until the brazing temperature is reached. Move the torch to area B and apply heat evenly until the brazing temperature has been reached there as well, and then begin adding the brazing material. Move the torch evenly around the joint, in applying only enough brazing material to flow the full circumference of the joint.

• Move the torch to area C only long enough to draw the brazing material into the joint, but not into the compressor.

• Remove all remaining flux once the joint has been soldered with a wire brush or a wet cloth. Remaining flux would cause corrosion of the tubing.

Ensure that no flux is allowed to enter into the tubing or compressor. Flux is acidic and can cause substantial damage to the internal parts of the system and compressor.

The PVE oil used in VRJ compressors is highly hygroscopic and will rapidly absorb moisture from the air. The compressor must therefore not be left open to the atmosphere for a long period of time. The compressor fitting plugs shall be removed just before brazing the compressor.

Before eventual unbrazing the compressor or any system component, the refrigerant charge must be removed from both the high and low pressure sides. Failure to do so may result in serious personal injury. Pressure gauges must be used to ensure all pressures are at atmospheric level.

For more detailed information on the appropriate materials required for brazing or soldering, please contact the product manufacturer or distributor. For specific applications not covered herein, please contact Danfoss Commercial Compressors for further information.

Moisture obstructs the proper functioning of both the compressor and the refrigeration system.

Air and moisture reduce service life and increase condensing pressure, which causes abnormally high discharge temperatures that are then capable of degrading the lubricating properties of the oil. The risk of acid formation is also increased by air and moisture, and this condition can also lead to copper plating. All these phenomena may cause both mechanical

and electrical compressor failures. The typical method for avoiding such problems is a vacuum pump-down executed with a vacuum pump, thus creating a minimum vacuum of 0.02 in Hg (500 µm Hg). Please refer to Bulletin “Vacuum pump down and dehydration procedure”.

Be sure to follow all government regulations regarding refrigerant reclamation and storage.

Compressor connection Heat shield

C B A


24 FRCC.PC.019.A2.22

Installation

Liquid line filter driers A properly sized filter drier is required for all Danfoss scroll applications. Danfoss recommends DML (100% molecular sieves) driers for HFC refrigerants R410A with PVE oil. For servicing of existing installations where acid formation is present the Danfoss DCL solid core filter driers

containing activated alumina are recommended. The drier is to be over sized rather than under sized. When selecting a drier, always take into account its capacity (water content capacity), the system refrigeration capacity and the system refrigerant charge.

Refrigerant charging

Insulation resistance and dielectric strength

Compressor replacement after motor burn out

It is recommended that system charging be done using the weighed charge method, adding refrigerant to the high side of the system. Charging the high and low sides of a system with gas simultaneously at a controlled rate is also an acceptable method.

Never exceed the recommended system charge mentioned by the unit manufacturer, and never charge liquid to the low pressure side.

Insulation resistance must be greater than 1 megohm when measured with a 500 volt direct current megohm tester.

Each compressor motor is tested at the factory with a high potential voltage (hi-pot) that exceeds the UL requirement both in potential and in duration. Leakage current is less than 0.5 mA.

VRJ scroll compressors are configured with the pump assembly at the top of the shell, and the motor below. As a result, the motor

can be partially immersed in refrigerant and oil. The presence of refrigerant around the motor windings will result in lower resistance values to ground and higher leakage current readings. Such readings do not indicate a faulty compressor, and should not be cause for concern.

In testing insulation resistance, Danfoss recommends that the system be first operated briefly to distribute refrigerant throughout the system. Following this brief operation, retest the compressor for insulation resistance or current leakage.

If there has been a motor burnout follow the evacuation procedure described on previous page. Remove and replace the liquid line filter drier and install a Danfoss type DAS burnout drier of appropriate capacity.

Refer to the DAS drier instructions and technical information on correct use and monitoring of the burnout drier and the liquid line and suction line filter driers.


25FRCC.PC.019.A2.22

Ordering information and packaging

Packaging Single pack

Compressors are packed individually in a cardboard box. They can be ordered in any quantity. Minimum ordering quantity = 1.

As far as possible, Danfoss will ship the boxes on full pallets of 6 compressors.

Each box contains following accessories:• 4 grommets• 4 assemblies of self tapping US thread bolts,

washers and sleeves

Industrial pack

Returnable pallet

Ordering code numbers

Compressors are not packed individually but are shipped all together on one pallet. They can be ordered in quantities of full pallets only, multiples 12 compressors.

Industrial pack pallet, with mounting hardware, contains following accessories:

• 4 grommets per compressor• 4 sleeves per compressor

As for industrial pack pallets, compressors are not packed individually but are shipped all together on one pallet. They can be ordered in quantities of full pallets only, multiples 16 compressors.Empty pallets must be returned to the compressor factory.

Returnable pallets contain neither rubber grommets, nor sleeves.

Compressor modelMounting hardware included Qty of compressors 3 Tons 4 Tons 5 Tons

VRJ028 VRJ035 VRJ044

Code

nu

mbe

r Single pack Yes 1 121U7003 121U7007 121U7011Industrial pack Yes 12 121U7000 121U7004 121U7008Returnable pallet No 16 120U7002 120U7006 120U7010

Danfoss Commercial Compressors is a worldwide manufacturer of compressors and condensing units for refrigeration and HVAC applications. With a wide range of high quality and innovative products we help your company to find the best possible energy efficient solution that respects the environment and reduces total life cycle costs.

We have 40 years of experience within the development of hermetic compressors which has brought us amongst the global leaders in our business, and positioned us as distinct variable speed technology specialists. Today we operate from engineering and manufacturing facilities spread across three continents.

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FRCC.PC.019.A2.22 - November 2014 - Replaces FRCC.PC.019.A1.22 - October 2010 © Copyright Danfoss | Commercial Compressors | 2014.11

Our products can be found in a variety of applications such as rooftops, chillers, residential air conditioners, heatpumps, coldrooms, supermarkets, milk tank cooling and industrial cooling processes.

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Danfoss Commercial Compressors, BP 331, 01603 Trévoux Cedex, France | +334 74 00 28 29

Documents

Application Guidelines - Danfossfiles.danfoss.com/technicalinfo/dila/17/FRCC.PC.019.A2.22-VRJ-Nov... · Application Guidelines ... Essential piping design considerations ... electronic