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8/12/2019 Heat Pumps Refrigeration Troubleshooting Manual
1/24
P.O. Box 245
Syracuse, NY 13211www.roth-america.com
888-266-7684
Refrigeration/Troubleshooting
Manual
Table of Contents:
Section 1: Geothermal Refrigeration
CircuitsOverview ................................................................ 2Water-to-Air Refrigerant Circuit ........................... 3
Refrig. Ckt. Component Operation .................... 3Water-to-Water Refrigerant Circuit ..................... 5Heating Operation ................................................ 6
Cooling Operation ................................................ 6Summary ................................................................ 8
Section 2: Heat of Extraction/Heat of
RejectionOverview ................................................................ 9Performance Data ................................................ 9Formulas ............................................................... 10
Examples .............................................................. 12
Section 3: Superheat/SubcoolingOverview .............................................................. 14Denitions ............................................................. 14
Checking Superheat and Subcooling .............. 14Putting It All Together .......................................... 15Pressure/Temperature Chart R-410A ................ 16Pressure/Temperature Chart R-22 ..................... 17
Superheat/Subcooling Measurements ............ 18Superheat/Subcooling Tables ........................... 19
Examples .............................................................. 20
Section 4: Desuperheater OperationOverview .............................................................. 22Desuperheater Cut-Away .................................. 22
Appendix A: Troubleshooting Form
P/N: 2300100910
Guide Revision Table:Date By Page Note
August, 2010 KT All First published
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exchanger (water-to-water and water-
to-air units) is connected to the groundloop or open loop (well water) system. Theload heat exchanger is connected to thehydronic load (for example, radiant oorheating) for water-to-water units. The loadheat exchanger in a water-to-air unit is theair coil, which is connected to duct work.
Overview
Geothermal heat pumps are available in avariety of congurations to provide exibilityfor installation in new construction orretrot applications. Most common in NorthAmerica are packaged water-to-air heatpumps, which provide forced air heatingand cooling. Packaged units (see gure 1)have the compressor section and the air
handler section in the same cabinet. Thereare also other types of geothermal heatpumps, such as water-to-water, which areused for radiant oor heating.
Water-to-water heat pumps heat or chillwater instead of heating or cooling the air
(see gure 5). The difference between awater-to-air and water-to-water heat pumpis the load heat exchanger. A secondwater-to-refrigerant coil is substituted forthe air to refrigerant coil. The source heat
Figure 1: Water-to-Air Refrigeration Circuit
Section 1: Geothermal Refrigeration Circuits
To suction line bulb
To suction line
AirCoil
Sucti
on
Coax
Discharge
Heating
Mode
AirCo
il
Suction
Coax
Discharge
Cooling
Mode
Liquid line (heating)
Liquid line (cooling)
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheater
installed in discharge line
(always disconnect during
troubleshooting)
Condenser (heating)
Evaporator (cooling)
Condenser (cooling)
Evaporator (heating)
Suction
Discharge
1
3
24
5 6
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Roth
Water-to-Air Refrigerant Circuit
The water-to-air geothermal heat pumprefrigerant circuit is very simple comparedto air source heat pumps. Defrost cycleis not required, and all components areindoors in a single cabinet. The maincomponents shown in gure 1 are thecompressor (1), the air coil (2), the coaxialheat exchanger (3), the reversing valve (4),
the TXV or thermal expansion valve (5), andthe lter drier (6).
Compressor:The compressor (1) is theheart of the system. The compressorpumps refrigerant through the circuit, andincreases the pressure of the refrigerant.
Since pressure and temperature are directlyrelated, when the pressure is increased, thetemperature is also increased. When thetemperature of the refrigerant is raised to ahigher temperature than the temperatureof the air owing through the air coil (2)in heating, heat is released to the air toheat the building. Likewise, when therefrigerant temperature is raised to a higher
temperature than the water owing throughthe coaxial heat exchanger (3) in cooling,
heat is released to the water.
Section 1: Geothermal Refrigeration Circuits
Roth uses Copeland Scroll compressors.
A scroll is an involute spiral which, whenmatched with a mating spiral scroll formas shown in gure 2, generates a series ofcrescent-shaped gas pockets between thetwo members. Scroll compressors work bymoving one spiral element inside anotherstationary spiral to create a series of gaspockets that become smaller and increase
the pressure of the gas.
The largest openings are at the outsideof the scroll where the gas enters on thesuction side. As these gas pockets areclosed off by the moving spiral they movetowards the center of the spirals andbecome smaller and smaller. This increases
the pressure on the gas until it reachesthe center of the spiral and is dischargedthrough a port near the center of the scroll.Both the suction process (outer portion ofthe scroll members) and the dischargeprocess (inner portion) are continuous.
The moving scroll moves in an orbitingpath within the stationary (xed) scroll as
it creates the series of gas pockets. Duringcompression, several pockets are being
compressed simultaneously, resulting in
Figure 2: Scroll Operation
Compression in the
scroll is created by the
interaction of an orbiting
spiral and a stationary
spiral. Gas enters the
outer openings as one
of the spirals orbits.
The open passages
are sealed off as gas is
drawn into the spiral.
As the spiral continues
to orbit, the gas is
compressed into
two increasingly
smaller pockets.
By the time the gas
arrives at the center
port, discharge pressure
has been reached.
Actually, during
operation, all six gas
passages are in various
stages of compression
at all times, resulting
in nearly continuous
suction and discharge.
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Section 1: Geothermal Refrigeration Circuits
a very smooth process. By maintaining
an even number (six in a Copeland Scrollcompressor) of balanced gas pockets onopposite sides, the compression forcesinside the scroll work to balance each otherand reduce vibration inside the compressor.
Single speed and two-stage (UltraTech)scroll compressors are used in Rothsproduct line. The two-stage scroll worksexactly like the single speed scroll shown ingure 2, but it has additional components,a solenoid valve, and bypass ports in thescroll mechanism. When the solenoid valveopens the bypass ports as shown in gure 3,the capacity is reduced to 67%, since partof the scroll is bypassed.
67% - PORTSOPEN 100% PORTSCLOSED
Figure 3: UltraTech Operation
Air Coil:The air coil (2), a refrigerant-to-airheat exchanger servers as the condenser inheating, and the evaporator in cooling.
Coaxial Heat Exchanger:The coaxial heatexchanger (3), a water-to-refrigerant heatexchanger, serves as the evaporator inheating, and the condenser in cooling.
Reversing Valve:The reversing valve (4)provides the ability to switch functionsof the two heat exchangers, above. As
shown in gure 1, the discharge line fromthe compressor is always connected to thebottom of the reversing valve. The centerconnection at the top is always connectedto the suction line from the compressor.The other two connections allow the heat
pump to switch from heating to cooling.
The normal (non-energized) mode isheating. Therefore, the discharge gas fromthe compressor ows to the air coil in thenon-energized mode. When the reversingvalve solenoid is energized in cooling, thevalve switches to allow the discharge gasfrom the compressor to ow to the coaxialheat exchanger.
The reversing valve is a pilot-operatedvalve, which means that the solenoidopens a small port, connecting thecopper tubing from the bottom port(discharge line from the compressor) to thevalve chamber. The high pressure of thedischarge line forces the valve to switch
from one mode to the other.
Thermal Expansion Valve (TXV):The TXV (5)meters refrigerant to make sure that theproper amount of refrigerant is being fed tothe heat exchangers in order to maximizethe condensing and evaporating functions.The TXV is also important in keeping liquidrefrigerant from reaching the suction line of
the compressor, which could damage thecompressor. The TXV is designed to operate
bi-directionally in packaged water-to-airand water-to-water heat pumps.
Diaphram
Valve Seat
Pin
4
4 = Liquid Pressure
(opening force)
Figure 4: TXV Operation
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Roth
Section 1: Geothermal Refrigeration Circuits
Figure 4 shows the operation of the TXV, andthe four forces that affect the operation.The TXV has two copper ttings forconnection to the air coil and coaxial heatexchanger, as well as two smaller copperlines that are used for metering. One lineis connected to a bulb that is attached tothe suction line of the compressor. The bulbis lled with refrigerant. As the suction linetemperature changes, the bulb pressurechanges. The other line is connecteddirectly to the suction line. The bulb pressure(force 1) pushes down on the diaphragmas the bulb pressure increases (suction linetemperature increases). When the pressurepushes down on the diaphragm, the pin(which is attached to the diaphragm) is
pushed away from the valve seat, whichopens the valve.
The other line, connected directly to thesuction line uses suction pressure (force 2) topush up on the diaphragm as the pressureincreases. As the diaphragm is pushed up,the pin is pushed into the valve seat, closing
To suction line bulb
To suction line
LoadC
oax
Suction
Source
Coax
Discharge
Heating
Mode
LoadC
oax
Suction
Source
Coax
Discharge
Cooling
Mode
Liquid line (heating)
Liquid line (cooling)
Load
Coax
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheater
installed in discharge line(always disconnect during
troubleshooting)
Condenser (heating)
Evaporator (cooling)
Condenser (cooling)
Evaporator (heating)
Suction
Discharge
Figure 5: Water-to-Water Refrigerant Circuit
the valve. This relationship of temperature(bulb pressure) and pressure (suction line)creates a balancing effect, which causesthe valve to meter at 0F superheat (seesection 3 for explanation of superheat).Since it is important to make sure that liquidis not returning to the compressor, the valvespring (force 3) is adjusted to fool thevalve into balancing at a higher superheat(usually 10 to 12F). Force 4 (liquid pressure)is an opening force.
Filter Drier:The lter drier (6) functionsexactly as its name implies. It lters anyparticles from the refrigerant system,and it pulls moisture from the system. It isextremely important that the lter drier is
changed any time the refrigerant circuitis open for a component replacement orrepair, especially for systems with R-410Arefrigerant. R-410A uses P.O.E. oil, whichis hygroscopic (tendency of a materialto absorb moisture from the air). Moisturecontaminates the refrigerant circuit overtime, and must be avoided.
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Section 1: Geothermal Refrigeration Circuits
Water-to-Water Refrigerant Circuit
The water-to-water heat pump refrigerantcircuit, as shown in gure 5, functionsexactly the same as the the water-to-airrefrigerant circuit with one exception. Theair coil is replaced by a second coaxialheat exchanger. The source coax isthe same as the water-to-air unit coax.However, the load coax heats or chills
water instead of heating or cooling the air.
Heating Operation
For the purposes of discussing the refrigerantcircuit operation in heating and coolingmodes, the water-to-air circuit will be used.
The other congurations directly apply withminor terminology/component changes.
In heating mode (see gure 7), thereversing valve is not energized. The hightemperature, high pressure refrigerant gasfrom the compressor ows to the air coil. Asthe air moves through the air coil, the cool(typically 70F) air causes the hot refrigerant
(typically 130 to 180F) to condense into aliquid. Thus, the air coil is the condenser in
the heating mode.
After leaving the air coil (condenser),the refrigerant is approximately thetemperature of the leaving air. Therefrigerant is within a few psi of being at thesame pressure as it was at the compressor
discharge line. This is the heating liquid line.The liquid line of a packaged unit changeslocation, depending upon the mode of
operation. It is always located betweenthe TXV and the condenser. However,since a geothermal unit is a heat pump,the condenser can either be the air coil(heating) or coaxial water coil (cooling).
At the TXV, the refrigerant is forced througha very small opening, which causes alarge pressure drop. As mentioned earlier,
pressure and temperature are directly
related, so the temperature also drops afterthe TXV. At this point, the refrigerant is alow temperature liquid (typically 15 to 50F,depending upon loop temperature).
The warm water (or water/antifreezesolution) owing through the coaxial heatexchanger (typically 30 to 60F) causes thecold refrigerant to boil off (evaporate)
into a gas or vapor. Thus, the coax is theevaporator in heating.
After leaving the coax (evaporator), therefrigerant is now approximately the sametemperature as the water entering theheat pump. This low pressure gas enters the
compressor, and the cycle starts allover again.
Proper refrigerant metering will insure thatno liquid is returned to the compressor.Section 3 discusses superheat andsubcooling, which allow the technicianto evaluate how well the condenser andevaporator are operating.
Cooling Operation
In cooling mode (see gure 8), thereversing valve must be energized. The hightemperature, high pressure refrigerant gasfrom the compressor ows to the coaxialheat exchanger. As the water (or water/antifreeze solution) ows through the coax,
the cool (typically 50 to 100F) water causesthe hot refrigerant (typically 130 to 180F) tocondense into a liquid. Thus, the coax is the
condenser in the cooling mode.
After leaving the coax (condenser),the refrigerant is approximately thetemperature of the water leaving thecoax. The refrigerant is within a few psi of
the compressor discharge line pressure.This is the cooling liquid line. The liquid lineof a packaged unit changes location,
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Section 1: Geothermal Refrigeration Circuits
To suction line bulb
To suction line
Liquid line (heating)
Liquid line (cooling)
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheater
installed in discharge line
(always disconnect during
troubleshooting)
Condenser (heating)
Evaporator (cooling)
Condenser (cooling)
Evaporator (heating)
Suction
Discharge
Figure 7: Heating Mode
Figure 8: Cooling Mode
To suction line bulb
To suction line
Liquid line (heating)
Liquid line (cooling)
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheater
installed in discharge line
(always disconnect duringtroubleshooting)
Condenser (heating)
Evaporator (cooling)
Condenser (cooling)
Evaporator (heating)
Suction
Discharge
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Section 1: Geothermal Refrigeration Circuits
depending upon the mode of operation. It
is always located between the TXV and thecondenser. However, since a geothermalunit is a heat pump, the condenser caneither be the air coil (heating) or coaxialwater coil (cooling).
At the TXV, the refrigerant is forced througha very small opening, which causes a largepressure drop. Once again, since pressure
and temperature are directly related, thetemperature also drops after the TXV. At thispoint, the refrigerant is a low temperatureliquid (typically 35 to 45F, depending uponreturn air temperature and air ow).
The warm air owing through the air coil
(typically 70 to 80F) causes the coldrefrigerant to boil off (evaporate) intoa gas or vapor. Thus, the air coil is theevaporator in cooling.
After leaving the air coil (evaporator), therefrigerant is now approximately the sametemperature as the air entering the heatpump. This low pressure gas enters thecompressor, and the cycle starts all
over again.
Summary
To summarize, refrigerant circuits ingeothermal heat pumps can be conguredfor packaged water-to-air, water-to-water,split systems or combination water-to-air
and water-to-water units. All circuits utilizea Copeland scroll (single or two-stage)compressor, one or two water-to-refrigerant
coaxial coils, an air-to-refrigerant coil, areversing valve, a bi-directional TXV, anda lter drier. Combination units include adirection valve and a 3-way valve to switchcondenser operation.
The air coil operates as the condenser inheating, and the evaporator in cooling.The source (loop) coax operates as the
condenser in cooling and the evaporator in
heating. Water-to-water units use a secondcoax instead of the air coil.
The reversing valve is energized in the cooling
mode. The non-energized mode is heating.
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Roth
Section 2: Heat of Extraction/Heat of Rejection
Overview
As mentioned in section 1, most geothermalheat pumps are packaged water-to-airheat pumps. Therefore, the refrigerantcircuit is evacuated and charged at thefactory, and there is no need to connectrefrigerant gauges unless the technicianhas veried that there is a refrigerantcircuit problem. Since connecting gauges
can cause a loss of charge and affectperformance, Roth recommends againstconnecting refrigerant gauges at startup.There are a number of checks that canbe made at startup to verify performancewithout connecting refrigerant gauges.
Heat of extraction is a calculation of theamount of heat that is being extracted or
absorbed from the water or water/anti-freeze solution by the evaporator (coaxialheat exchanger) in the heating mode.Heat of rejection is the amount of heatthat is being rejected to the water by thecondenser (coaxial heat exchanger) in thecooling mode. In addition to measuring thetemperature rise or drop across the air coil,calculating heat of extraction or heat of
rejection allows the technician to verify thatthe heat pump is performing according tospecications. If the calculation shows thatthe heat pump is performing poorly, thenrefrigeration gauges may be required tofurther troubleshoot the problem.
Performance Data
Before discussing heat of extraction (HE)
/ heat of rejection (HR) calculations, thetechnician should understand how to usethe performance data in the catalog tocompare the unit specications to actualcalculations.
Figures 9 and 10 show performance data
for a typical 3 ton geothermal water-to-air heat pump. the highlighted columns
indicate HE and HR. In gure 9, HE is theamount of heat that is being extracted
from the water (for example, ground loop)by the refrigerant circuit. The compressorand fan power (kW column) is used tooperate the refrigerant circuit. The heatdelivered to the space (HC column) equalsthe HE from the water plus the waste heatof the power used for compressor and fan.If the kW is converted to Btuh, and added
to the HE, the sum should equal HC.
For example, in gure 9, at 30F EWT, 9.0GPM and 70F EAT, the heating capacityis 30,700 Btuh. HE is 21,800 Btuh. If the kW(2.63) is converted to Btuh (2.63 x 3.412 =8.97 MBtuh or 8,970 Btuh), and added to
HE, the result is HC. Therefore, if HE is within,10-15% of catalog performance, HC should
also be within specications. There is noneed to connect refrigerant gauges if HE iswithin specications.
In gure 10, HR is the amount of heat that isbeing rejected to the water (for example,ground loop) by the refrigerant circuit. Thecompressor and fan power (kW column) isused to operate the refrigerant circuit. The
heat rejected from the space (HR column)equals the heat from the air (TC column --amount of cooling) plus the waste heat ofthe power used for compressor and fan. Ifthe kW is converted to Btuh, and added tothe TC, the sum should equal HR.
For example, in gure 10, at 90F EWT, 9.0GPM and 75F DB/63F WB (50% RH), HRis 43,400 Btuh. TC is 34,400 Btuh. If the kW
(2.73) is converted to Btuh (2.73 x 3.412 =9.31 MBtuh or 9310 Btuh), and added toTC, the result is HR. Thefore, if HR is within,10-15% of catalog performance, TC shouldalso be within specications. There is noneed to connect refrigerant gauges if HR iswithin specications.
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Formulas
The formula is the same for HE and HR.The amount of heat being extractedor rejected can be calculated if thetemperature difference between waterentering and leaving the coaxial heatexchanger (TD) is known, and the waterow (GPM) is measured. The only other itemneeded is the type of antifreeze. A uid
factor is used to represent the specic heatof the water/antifreeze solution, as well asto convert the units (GPM and F) to Btuh.
HE or HR (Btuh) = GPM x TD x Fluid Factor
Where: GPM = Flow rate in U.S. gallons per
minute TD = Temp. diff. (between water in& out) Fluid Factor = 500 for water; 485 formost antifreezesFigures 11 and 12 show the tools requiredfor checking HE and HR.All techniciansinstalling and servicing geothermal heatpumps should have at least one set ofthese tools.
Flow rate can be determined by measuringthe pressure drop across the coaxial heat
exchanger. The pressure gauge and adaptershould be inserted into the P/T (pressure/temperature) port of the Water INconnection. Record the reading. Next, insert
the gauge into the Water OUT port, andrecord the reading. The difference betweenthe IN and OUT is the pressure drop.
Once the pressure drop of the heatexchanger is known, the ow rate can be
determined by consulting the performancedata for the particular unit.
Example:
In heating mode, model 036 has EWT of50F, water pressure IN of 40 psi, and waterpressure OUT of 35 psi. The pressure drop,therefore is 5 psi. Figure 10 shows three
water pressure drop values and three water
ow rates. At 50F, if the pressure drop is 1.7psi, the ow rate would be 5.0 GPM; if thepressure drop is 3.1 psi, the ow rate wouldbe 7.0 GPM; and if the pressure drop is 5.0psi, the ow rate would be 9.0 GPM. The owrate in this example is 9.0 GPM. Rarely arethe temperature and pressure drop exactlyas shown in the tables, so there will be some
interpolation required (for example, 52F EWTand 4.7 psi pressure drop).
NOTE: A large gauge face is preferred,since it will be easier to read pressures tothe nearest 0.5 psi. ALWAYS use the samegauge in the IN and OUT connections.The use of two gauges could cause false
readings, since they could both be out ofcalibration in opposite directions. Neverforce the gauge adapter into the P/T port.The gauge adapter could break off in theP/T port, or the force could cause the ringholding the P/T port bladder to becomedislodged, potentially ending up in apump impeller.
Once the ow rate is determined, thepocket thermometer can be used to obtain
TD. Insert the thermometer into the WaterIN P/T port. Record the temperature. Insertthe thermometer into the Water OUTport, and record the temperature. Thedifference between the IN and OUTis the TD. In heating, EWT (entering watertemperature) will be warmer than LWT
(leaving water temperature); in cooling itwill be just the opposite.
The last item needed is the type of uidcirculating through the heat pump. Asmentioned earlier, 500 should be used forpure water (open loop/well water systems).Use 485 for most antifreeze solutions (see
Flow Center and Loop Application Manualfor details on antifreeze solutions).
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Roth
Section 2: Heat of Extraction/Heat of Rejection
036 Performance Data:3.0 Ton, 1200 CFM, Heating
EWT GPMretaehrepuseDhtiwgnitaeHgnitaeHDPW
PSI FT EAT HC HE LAT KW COP HC HE LAT KW DH COP
30
5.0 1.8 4.2
60 30.2 21.7 83.3 2.47 3.58 26.5 21.7 80.4 2.45 3.8 3.62
70 29.4 20.4 92.7 2.61 3.30 25.5 20.5 89.7 2.56 3.9 3.36
80 28.4 19.2 101.9 2.73 3.05 24.4 19.3 98.9 2.68 4.0 3.11
7.0 3.4 7.8
60 31.1 22.6 84.0 2.50 3.65 27.3 22.7 81.0 2.45 3.9 3.73
70 30.3 21.3 93.4 2.63 3.37 26.3 21.4 90.3 2.58 4.0 3.44
80 29.4 20.0 102.7 2.77 3.12 25.3 20.1 99.5 2.7 4.1 3.19
9.0 5.4 12.5
60 31.5 23.0 84.3 2.50 3.70 27.6 23.2 81.3 2.44 3.9 3.78
70 30.7 21.8 93.7 2.63 3.42 26.6 18.7 90.6 2.58 4.1 3.49
80 29.9 20.4 103.1 2.76 3.17 25.7 20.5 99.8 2.71 4.2 3.23
50
5.0 1.7 3.9
60 39.1 30.3 90.2 2.59 4.42 34.2 30.6 86.4 2.51 4.9 4.57
70 37.9 28.5 99.3 2.73 4.07 32.9 28.8 95.4 2.65 5.0 4.2080 36.6 26.8 108.3 2.86 3.75 31.5 27.1 104.3 2.78 5.1 3.86
7.0 3.1 7.2
60 40.7 31.7 91.4 2.64 4.52 35.7 32.1 87.5 2.56 5.1 4.67
70 39.4 30.0 100.4 2.78 4.15 34.2 30.2 96.4 2.69 5.2 4.29
80 38.1 28.1 109.4 2.93 3.82 32.8 28.4 105.3 2.83 5.4 3.95
9.0 5.0 11.6
60 41.6 32.6 92.1 2.65 4.59 36.4 32.8 88.1 2.56 5.2 4.76
70 40.2 30.7 101.1 2.79 4.22 34.9 31.1 96.9 2.70 5.3 4.36
80 38.9 28.9 110 2.94 3.88 33.4 29.2 105.8 2.84 5.5 4.01
Entering
Water
Temp (F)
Flow
Rate
(U.S. GPM)
Water
Press. Drop
(PSI & Ft. of Head)
Entering
Air
Temp (F)
Heating
Capacity
(MBtuh)
Heat of
Extraction
(MBtuh)
Leaving
Air
Temp (F)
Input
Power (kW)
Coefficient
of
Performance
Desuperheater
Capacity
(MBtuh)
Figure 9: Typical Performance Data - Heating Mode
036 Performance Data:3.0 Ton, 1200 CFM, Cooling
EWT GPM
WPD EAT
DB/WB
retaehrepuseDhtiwgnilooCgnilooC
PSI FT TC SC HR KW EER TC SC HR KW DH EER
70
5.0 1.7 3.9
75/63 36.7 26.8 44.8 2.41 15.2 36.9 26.9 44.9 2.35 4.7 15.7
80/67 39.8 27.9 47.6 2.47 16.1 40.0 28.0 47.7 2.40 4.9 16.7
85/71 43.0 29.0 50.5 2.51 17.2 43.3 29.1 50.6 2.46 5.1 17.6
7.0 3.0 6.9
75/63 37.2 27.1 45.0 2.29 16.2 37.4 27.2 45.1 2.26 4.6 16.6
80/67 40.5 28.2 47.9 2.34 17.3 40.4 28.3 48.0 2.31 4.7 17.6
85/71 43.7 29.3 50.8 2.39 18.3 43.9 29.5 50.9 2.34 4.8 18.7
9.0 4.8 11.1
75/63 37.6 27.1 45.2 2.22 16.9 37.8 27.2 45.4 2.21 4.3 17.1
80/67 40.9 28.2 48.1 2.27 18.0 41.1 28.3 48.3 2.26 4.5 18.2
85/71 44.1 29.3 50.9 2.32 19.0 44.3 29.5 51.2 2.30 4.7 19.3
90
5.0 1.6 3.6
75/63 33.4 25.7 43.1 2.98 11.2 33.7 25.9 43.3 2.89 6.3 11.7
80/67 36.3 26.8 45.9 3.04 11.9 36.6 27.0 46.0 2.95 6.4 12.4
85/71 39.2 27.9 48.7 3.09 12.7 39.5 28.0 48.8 3.01 6.6 13.2
7.0 2.8 6.4
75/63 34.0 26.0 43.4 2.81 12.1 34.3 26.2 43.6 2.75 6.0 12.5
80/67 37.0 27.1 46.1 2.87 12.9 37.3 27.2 46.3 2.80 6.2 13.3
85/71 40.0 28.1 48.8 2.92 13.7 40.4 28.3 49.2 2.87 6.3 14.1
9.0 4.5 10.3
75/63 34.4 26.0 43.4 2.73 12.6 34.7 26.2 43.8 2.70 5.8 12.9
80/67 37.4 27.1 46.2 2.78 13.4 37.8 27.2 46.6 2.75 5.9 13.7
85/71 40.4 28.1 49.0 2.85 14.2 40.8 28.3 49.4 2.80 6.1 14.5
Total Cooling, (MBtuh)
= SC + LC (Latent Cap)
Sensible Cooling
(MBtuh)
Heat of
Rejection
(MBtuh)
Input
Power (kW)
Energy
Efficiency
Ratio
Figure 10: Typical Performance Data - Cooling Mode
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Section 2: Heat of Extraction/Heat of Rejection
Figure 13 includes an example water-to-air
heat pump in heating mode; gure 14 showsthe same heat pump in cooling. Followingare two examples based upon these gures,which are shown on the next page.
Example 1: Model 036, ground loop systemwith ProCool (ethanol) antifreeze solution,heating mode.
1) Fluid factor = 4852) EWT = 30.0F LWT = 23.5F TD = 6.5F3) Pressure IN = 40 psi Pressure OUT = 36.6 psi Pressure drop = 3.4 psi From performance data, GPM = 7.04) HE = GPM x TD x Fluid Factor
HE = 7.0 x 6.5 x 485 = 22,067 Btuh
Catalog HE = 21,300 Btuh. Therefore, unit is
Pocket Thermometer
P/N TSDT or equivalent
Figure 11: Pressure Gauge with Adapter
performing better than specications.
Example 2:Model 036, ground loop systemwith ProCool (ethanol) antifreeze solution,cooling mode.
1) Fluid factor = 4852) EWT = 90.0F LWT = 101.2F TD = 11.2F3) Pressure IN = 40 psi
Pressure OUT = 36.3 psi Pressure drop = 3.7 psi From performance data, GPM = 8.04) HR = GPM x TD x Fluid Factor HR = 8.0 x 11.2 x 485 = 43,456 Btuh
Catalog HR = 43,400 Btuh. Therefore, unit isperforming better than specications.
NOTE: HE and HR should be within 10-15% ofcatalog values.
Figure 12: Pocket Thermometer
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Section 2: Heat of Extraction/Heat of Rejection
To suction line bulb
To suction line
Air
Coil
Suction
Coax
Discharge
Heating
Mode
Air
Coil
Suc
tion
Coa
x
Discharge
Cooling
Mode
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
F
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water units
substitute a second coaxial
heat exchanger for the air coil.
Load
Coax
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheater
installed in discharge line
(always disconnect duringtroubleshooting)
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
FSupply Air
F
GPM
GPM
101.2
36.3
90.0
40.075.0 55.0
To suction line bulb
To suction line
AirCoil
Suction
Coax
Discharge
Heating
Mode
AirCoil
Suction
Coax
Discharge
Cooling
Mode
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
F
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water units
substitute a second coaxialheat exchanger for the air coil.
Load
Coax
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheater
installed in discharge line(always disconnect during
troubleshooting)
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
FSupply Air
F
GPM
GPM
23.5
36.6
30.0
40.070.0 93.4
Figure 13: Heating Operation Example
Figure 14: Cooling Operation Example
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Section 3: Superheat/Subcooling
Overview
Superheat and subcooling are used todetermine if the heat pump has the properrefrigerant charge, as well as for verifyingthat the condenser and evaporatorare performing properly. Superheatand subcooling can even be used totroubleshoot refrigerant circuit blockages or
a bad TXV.
Defnitions
Saturation Temperature:Saturationtemperature, sometimes called boilingpoint, is the temperature at which arefrigerant changes state. For example,
Table 1 shows that refrigerant R-410A hasa saturation temperature of 32F at 100psi. Therefore, the refrigerant at 100 psi is aliquid if it is below 32F, and a gas (vapor) ifit is above 32F.
Superheat: Superheat is dened as thenumber of degrees above the saturationtemperature of a refrigerant. For example,
if the temperature of refrigerant R-410A is40F at 100 psi, it has 8F of superheat, since
the saturation temperature is 32F.
Subcooling:Subcooling is dened as thenumber of degrees below the saturationtemperature of a refrigerant. For example,if the temperature of refrigerant R-410A
is 28F at 100 psi, it has 4F of subcooling,since the saturation temperature is 32F.
Checking Superheat and Subcooling
Superheat and subcooling should only bechecked after the heat of extraction orheat of rejection calculations (see section2) indicate that the unit is performing
poorly. Connecting refrigerant gaugesshould be done as a last resort.
Checking superheat and subcooling requiresa refrigeration gauge set with manifold andhoses, plus a digital thermocouple typethermometer. Heat pumps produced byRoth have two schrader ports for serviceconnections, one at the discharge line ofthe compressor, and one at the suction line
of the compressor. When these pressuresare used in conjunction with the suction linetemperature and liquid line temperature,superheat and subcooling can becalculated. Insulation should be removedfrom the suction line and liquid line, and thecopper should be free from insulation glue,so that the thermocouple makes a good
connection at the copper line.
Figures 15a and 15b illustrate the locationsfor taking pressure and temperaturemeasurements. Notice that the two areasfor temperature measurement are suctionline and liquid line. In order to checksuperheat and subcooling, the saturationtemperature must be determined, whichrequires the pressure of the refrigerant andthe actual temperature of the refrigerant
at the same location. However, the onlylocation where both temperature and
pressure are easily obtained is at thesuction line. In section 1, temperaturesand pressures were discussed in relationto components, both before and afterthe components. It was also mentionedthat the discharge pressure and theliquid line pressure are within a few psi
of each other. Most manufacturers ofpackaged equipment adjust their servicedata to allow the technician to use the
discharge pressure as the liquid linepressure. Therefore, for checking superheatand subcooling, use discharge pressurewith liquid line temperature, and suctionpressure with suction temperature.
Although superheat and subcooling canbe calculated anywhere in the refrigeration
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Section 3: Superheat/Subcooling
circuit, there are two points that are mostuseful for troubleshooting purposes. First ofall, it is imperative that liquid is not returnedto the compressor. Liquid refrigerantwill wash some of the compressor oilaway from critical internal parts, causingpremature compressor failure. Plus, thecompressor is designed to pump gas, notliquid, and will be operating under adverse
conditions. Checking for superheat at thesuction line of the compressor insures thatthe state of the refrigerant at this point isa gas (vapor). The amount of superheatat the suction line determines how wellthe evaporator (coax in heating, air coil incooling) is working. Superheat is normallyin the 8 to 12F range, but the installation
manual will provide specic information forthe unit being serviced. NOTE: Check thetemperature of the suction line near theTXV bulb, especially on split systems.
The other location to check is the liquidline. Since the liquid line is located afterthe condenser (air coil in heating, coaxin heating), the amount of subcooling
determines how well the condenser isworking. In most cases subcooling is in the
4 to 10F range, but the installation manualwill provide specic information for the unitbeing serviced.
Putting It All Together
In section 1, TXV operation was discussed.Since the TXV spring has been adjustedto maintain 8 to 12F of superheat, it willclose down when necessary to maintain
the predetermined superheat setting.Therefore, subcooling plays a crucial part inevaluating the units refrigeration charge. Inother words, if the unit is overcharged, theTXV will close down to maintain superheat,
backing up liquid refrigerant in thecondenser. If only superheat is measured,the technician would not know that the unit
is overcharged. If subcooling is measured,the high value would indicate that thereis a problem with the refrigeration charge.Table 3 lists the conditions associated withhigh or low superheat and subcooling.Table 4 is an example of typical data foundin the installation manual.
Figures 16 through 18 illustrate examples
of a normally charged system, anundercharged system, and anovercharged system.
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Section 3: Superheat/Subcooling
Saturation Saturation Saturation
Pressure Temp (F) Pressure Temp (F) Pressure Temp (F)PSIG R-410A PSIG R-410A PSIG R-410A
0 -60 125 43 370 111
2 -58 130 45 375 112
4 -54
135 47
380 113
6 -50 140 49 385 114
8 -46 145 51 390 115
10 -42 150 53 395 11612 -39 155 55 400 117
14 -36 160 57 405 11816 -33 165 59 410 119
18 -30 170 60 415 120
20 -28 175 62 420 12122 -26 180 64 425 122
24 -24 185 66 430 12226 -20 190 67 435 123
28 -18 195 69 440 124
30 -16 200 70 445 12532 -14 205 72 450 126
34 -12 210 73 455 12736 -10 215 75 460 128
38 -8 220 76 465 129
40 -6 225 78 470 13042 -4 230 79 475 130
44 -3 235 80 480 13146 -2 240 82 485 132
48 0 245 83 490 133
50 1 250 84 495 13452 3 255 85 500 134
54 4 260 87 505 135
56 6 265 88 510 13658 7 270 89 515 137
60 8 275 90 520 13862 10 280 91 525 138
64 11 285 92 530 139
66 13 290 94 535 140
68 14 295 95 540 141
70 15 300 96 545 14272 16 305 97 550 142
74 17 310 98 555 143
76 19 315 99 560 144
78 20 320 100 565 145
80 21 325 101 570 14685 24 330 102 575 146
90 26 335 104 580 147
95 29 340 105 585 148
100 32 345 106 590 149
105 34 350 108 595 149110 36 355 108 600 149
115 39 360 109 650 154120 41 365 110 700 159
Table 1: Pressure/Temperature Chart, R-410A Refrigerant
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Section 3: Superheat/Subcooling
Saturation Saturation Saturation
Pressure Temp (F) Pressure Temp (F) Pressure Temp (F)PSIG R-22 PSIG R-22 PSIG R-22
0 -41 90 54 300 132
2 -37 95 56 305 133
4 -32
100 59
310 134
6 -28 105 62 315 135
8 -24 110 64 320 136
10 -20 115 67 325 13712 -17 120 69 330 138
14 -14 125 72 335 14016 -11 130 74 340 141
18 -8 135 76 345 142
20 -5 140 78 350 14422 -3 145 81 355 144
24 0 150 83 360 14526 2 155 85 365 146
28 5 160 87 370 147
30 7 165 89 375 14832 9 170 91 380 149
34 11 175 93 385 15136 13 180 94 390 152
38 15 185 96 395 153
40 17 190 98 400 15542 19 195 100 405 155
44 21 200 101 410 15646 23 205 103 415 158
48 24 210 105 420 159
50 26 215 107 425 16052 28 220 108 430 160
54 29 225 110 435 161
56 31 230 112 440 16258 32 235 113 445 163
60 34 240 115 450 16462 35 245 116 455 165
64 37 250 118 460 167
66 38 255 119 465 168
68 40 260 120 470 169
70 41 265 121 475 16972 42 270 123 480 170
74 44 275 124 485 171
76 45 280 126 490 172
78 46 285 127 495 173
80 48 290 129 500 17385 51 295 130
Table 2: Pressure/Temperature Chart, R-22 Refrigerant
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Section 3: Superheat/Subcooling
F
To suction line bulb
To suction line
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water units
substitute a second coaxialheat exchanger for the air coil.
Load
Coax
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheaterinstalled in discharge line
(always disconnect duringtroubleshooting)
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
FSupply Air
F
GPM
GPM
R-410A Manifold/Gauge Set
Suction Discharge
F
Thermometer
1
2
21
To suction line bulb
To suction line
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
F
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water units
substitute a second coaxialheat exchanger for the air coil.
Load
Coax
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheaterinstalled in discharge line
(always disconnect duringtroubleshooting)
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
FSupply Air
F
GPM
GPM
R-410A Manifold/Gauge Set
Suction Discharge
F
Thermometer
1
2
21
Figure 15a: Superheat/Subcooling Measurement - Heating
Figure 15b: Superheat/Subcooling Measurement - Cooling
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Superheat Subcooling Condition
Normal Normal Normal operation
Normal High Overcharged
High Low Undercharged
High High Restriction or TXV is stuck almost closedLow Low TXV is stuck open
Heating - Without Desuperheater
EWT GPM
Per Ton
Discharge
Pressure
(PSIG)
Suction
Pressure
(PSIG)
Sub
Cooling
Super
Heat
Air
Temperature
Rise (F-DB)
Water
Temperature
Drop (F)
301.5
3
285-310
290-315
68-76
70-80
4-10
4-10
8-12
8-12
14-20
16-22
5-8
3-6
50
1.5
3
315-345
320-350
100-110
105-115
6-12
6-12
9-14
9-14
22-28
24-30
7-10
5-8
701.5
3
355-395
360-390
135-145
140-150
7-12
7-12
10-15
10-15
30-36
32-38
9-12
7-10
Cooling - Without Desuperheater
EWT GPM
Per Ton
Discharge
Pressure
(PSIG)
Suction
Pressure
(PSIG)
Sub
Cooling
Super
Heat
Air
Temperature
Drop (F-DB)
Water
Temperature
Rise (F)
501.5
3
220-235
190-210
120-130
120-130
10-16
10-16
12-20
12-20
20-26
20-26
19-23
9-12
701.5
3
280-300
250-270
125-135
125-135
8-14
8-14
10-16
10-16
19-24
19-24
18-22
9-12
Table 3: Superheat/Subcooling Conditions
Table 4: Typical R-410A Unit Superheat/Subcooling Values
Section 3: Superheat/Subcooling
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Section 3: Superheat/Subcooling
Figure 16: Normally-Charged System, Heating Mode
Figure 17: Under-Charged System, Heating Mode
To suction line bulb
To suction line
AirCoil
Suction
Coax
Discharge
Heating
Mode
AirCoil
Suction
Coax
Discharge
Cooling
Mode
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
F
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water units
substitute a second coaxialheat exchanger for the air coil.
LoadCoax
AirCoil
TXV
Filter Drier
Reversing
Valve
SourceCoax
Optional desuperheater
installed in discharge line(always disconnect during
troubleshooting)
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
FSupply Air
F
GPM
GPM
30.0
40.0
7.0
23.5
36.6
76 19
300
29
90.0
70.0
Superheat =
29 - 19 = 10F
Subcooling =
96 - 90 = 6F
To suction line bulb
To suction line
AirCoil
Suction
Coax
Discharge
Heating
Mode
AirCoil
Suction
Coax
Discharge
Cooling
Mode
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
F
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water units
substitute a second coaxialheat exchanger for the air coil.
Load
Coax
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheater
installed in discharge line(always disconnect during
troubleshooting)
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
FSupply Air
F
GPM
GPM
30.0
40.0
7.0
26.5
36.6
68 14
260 87
29
87.0
70.0 90.0
Superheat =
29 - 14 = 15F
Subcooling =
87 - 87 = 0F
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Roth
Section 3: Superheat/Subcooling
Figure 18: Over-Charged System, Heating Mode
To suction line bulb
To suction line
AirCoil
Suction
Coax
Discharge
Heating
Mode
AirCoil
Suction
Coax
Discharge
Cooling
Mode
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
F
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water units
substitute a second coaxial
heat exchanger for the air coil.
LoadCoax
AirCoil
TXV
Filter Drier
Reversing
Valve
SourceCoax
Optional desuperheater
installed in discharge line
(always disconnect duringtroubleshooting)
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
FSupply Air
F
GPM
GPM
30.0
40.0
26.5
36.6
85 24
325 101
34
85.0
70.0 90.0
Superheat =
34 - 24 = 10F
Subcooling =
101 - 85=16F
Figure 19: Water-to-Air Refrigerant Circuit with Desuperheater
To suction line bulb
To suction line
AirCoil
Suction
Coax
Discharge
Heating
Mode
AirCoil
Suction
Coax
Discharge
Cooling
Mode
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
F
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water unitssubstitute a second coaxial
heat exchanger for the air coil.
Load
Coax
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
FSupply Air
F
GPM
GPM
Desuperheater
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Section 4: Desuperheater Operation
The desuperheater option includes a water-to-refrigerant coaxial heat exchangerinstalled between the compressordischarge line and reversing valve,which is connected to the condenser(air coil in heating, coax in cooling) asshown in gure 19. Unlike the sourcecoax in all Roth geothermal heat pumps,the desuperheater coax is a double-
wall, vented water-to-refrigeration heatexchanger. Figure 20 illustrates a cut-awayof the desuperheater coax.
The operation of the desuperheatertakes advantage of the superheat atthe discharge line. For example, in gure16, the discharge pressure is 300 psi. The
saturation temperature at 300 psi is 96F.The discharge line at these conditionswould typically be around 160F. Therefore,the superheat (actual temperature saturation temperature) is 64F. Asdomestic hot water ows through thedesuperheater heat exchanger, some ofthe superheat at the discharge line is usedto heat domestic water, which lowers the
superheat at the discharge line, thus theterm desuperheater.
Water ow rate through the desuperheatercoax must be very low to avoid turningthe desuperheater into a condensor, androbbing too much heat from the maincondenser. Typically, about 0.4 GPM per
ton is used for desuperheater ow rate. Thedesuperheater pump operates anytime thecompressor is operating (unless the one ofthe temperature limits is open).
In cooling, the desuperheater takes someof the heat that would have been rejectedto the ground loop via the condenser(coax), and uses it to make domestic
hot water. Therefore, the desuperheaterproduces nearly free hot water (otherthan the fractional horsepower circulatingpump) in the cooling mode.
In heating, the desuperheater takes someof the heat that would have been usedto heat the space via the condenser (aircoil), and uses it to make domestic hotwater. Even though the desuperheateris robbing some of the heat from thespace, it is a very small amount, and thesystem is heating water at a very highC.O.P. (3.0 to 4.0, depending upon loop
temperature), compared to an electricwater heater at a C.O.P. of 1.0.
Some geothermal heat pumps turn off thedesuperheater pump when back up heatis energized. However, studies show that onan annual basis, the system is more energyefcient when the desuperheater is utilized
any time the compressor is running. Whenthe hot water tank is already heated, athermal switch turns off the desuperheaterpump. The pump may also be turned off ifthe compressor discharge line is too cool.
Figure 20: Desuperheater coax cut-away
Steel Outer Wall
Rifled Copper Tube
Smooth Wall
Inner Tube
Refrigerant
Air Gap
Water
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Troubleshooting Form
Please make copies of this form.
Diagram: Water-to-Air and Water-to-Water Units
Customer/Job Name:____________________________________________ Date:________________________________
Model #:__________________________________________ Serial #:____________________________________________
Antifreeze Type:____________________________________
HE or HR = GPM x TD x Fluid Factor(Use 500 for water; 485 for antifreeze)
SH = Suction Temp. - Suction Sat. SC = Disch. Sat. - Liq. Line Temp.
To suction line bulb
To suction line
AirCoil
Suction
Coax
Discharge
Heating
Mode
AirCoil
Suction
Coax
Discharge
Cooling
Mode
Liquid line (heating)
F
Liquid line (cooling)
F
Discharge Line
psi
(saturation)
F
Suction Line
psi
(saturation)
F
Suction temp
F
For water-to-water units
substitute a second coaxial
heat exchanger for the air coil.
Load
Coax
AirCoil
TXV
Filter Drier
Reversing
Valve
Source
Coax
Optional desuperheaterinstalled in discharge line
(always disconnect during
troubleshooting)
Source (loop) IN
Source (loop) OUT
F
psi
F
psi
Load IN
F
psi
Load OUT
F
psi
Return Air
F
Supply Air
F
GPM
GPM
Note: DO NOT connect
refrigerant gaugesuntil Heat of Extraction
or Rejection has beenchecked.
Note: Disconnect desuperheater before proceeding
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P.O. Box 245
Syracuse, NY 13211
888-266-7684 US
800-969-7684 CAN
866-462-2914 FAX
www.roth-america.com
*AHRI certication is shown as the Roth brand under the Enertech Manufacturing certication reference number**Roth Industries geothermal heat pumps are shown as a multiple listing of Enertech Manufacturings ETL certication
*** Roth geothermal heat pumps are listed as a brand under Enertech Manufacturings Energy Star ratings
*
*****