Heat Pumps Refrigeration Troubleshooting Manual

8/12/2019 Heat Pumps Refrigeration Troubleshooting Manual

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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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2Roth Refrigeration/Troubleshooting Guide,August, 2010

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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3Refrigeration/Troubleshooting GuideAugust, 2010

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.


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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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


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

LoadC

oax

Suction

Source

Coax

Discharge

Heating

Mode

LoadC

oax

Suction

Source

Coax

Discharge

Cooling

Mode



Load

Coax

TXV

Filter Drier

Reversing

Valve

Source

Coax


installed in discharge line(always disconnect during

troubleshooting)

Condenser (heating)


Condenser (cooling)


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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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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Roth



To suction line



AirCoil

TXV

Filter Drier

Reversing

Valve

Source

Coax




troubleshooting)

Condenser (heating)


Condenser (cooling)


Suction

Discharge

Figure 7: Heating Mode

Figure 8: Cooling Mode


To suction line



AirCoil

TXV

Filter Drier

Reversing

Valve

Source

Coax



(always disconnect duringtroubleshooting)

Condenser (heating)


Condenser (cooling)


Suction

Discharge


8/24



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.


10/24


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).


11/24


Roth


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


12/24



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


13/24


Roth



To suction line

Air

Coil

Suction

Coax

Discharge

Heating

Mode

Air

Coil

Suc

tion

Coa

x

Discharge

Cooling

Mode


F


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




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

AirCoil

Suction

Coax

Discharge

Heating

Mode

AirCoil

Suction

Coax

Discharge

Cooling

Mode


F


F

Discharge Line

psi

(saturation)

F

Suction Line

psi

(saturation)

F

Suction temp

F


substitute a second coaxialheat exchanger for the air coil.

Load

Coax

AirCoil

TXV

Filter Drier

Reversing

Valve

Source

Coax



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


14/24


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


15/24


Roth


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.


16/24



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


17/24


Roth


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


18/24



F


To suction line


F


F

Discharge Line

psi

(saturation)

Suction Line

psi

(saturation)

F

Suction temp

F



Load

Coax

AirCoil

TXV

Filter Drier

Reversing

Valve

Source

Coax

Optional desuperheaterinstalled in discharge line


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


F


F

Discharge Line

psi

(saturation)

F

Suction Line

psi

(saturation)

F

Suction temp

F



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

R-410A Manifold/Gauge Set

Suction Discharge

F

Thermometer

1

2

21

Figure 15a: Superheat/Subcooling Measurement - Heating

Figure 15b: Superheat/Subcooling Measurement - Cooling


19/24


Roth

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



20/24



Figure 16: Normally-Charged System, Heating Mode

Figure 17: Under-Charged System, Heating Mode


To suction line

AirCoil

Suction

Coax

Discharge

Heating

Mode

AirCoil

Suction

Coax

Discharge

Cooling

Mode


F


F

Discharge Line

psi

(saturation)

F

Suction Line

psi

(saturation)

F

Suction temp

F



LoadCoax

AirCoil

TXV

Filter Drier

Reversing

Valve

SourceCoax



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

AirCoil

Suction

Coax

Discharge

Heating

Mode

AirCoil

Suction

Coax

Discharge

Cooling

Mode


F


F

Discharge Line

psi

(saturation)

F

Suction Line

psi

(saturation)

F

Suction temp

F



Load

Coax

AirCoil

TXV

Filter Drier

Reversing

Valve

Source

Coax



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


21/24


Roth


Figure 18: Over-Charged System, Heating Mode


To suction line

AirCoil

Suction

Coax

Discharge

Heating

Mode

AirCoil

Suction

Coax

Discharge

Cooling

Mode


F


F

Discharge Line

psi

(saturation)

F

Suction Line

psi

(saturation)

F

Suction temp

F




LoadCoax

AirCoil

TXV

Filter Drier

Reversing

Valve

SourceCoax




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

AirCoil

Suction

Coax

Discharge

Heating

Mode

AirCoil

Suction

Coax

Discharge

Cooling

Mode


F


F

Discharge Line

psi

(saturation)

F

Suction Line

psi

(saturation)

F

Suction temp

F

For water-to-water unitssubstitute a second coaxial


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


22/24


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


23/24


Roth

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

AirCoil

Suction

Coax

Discharge

Heating

Mode

AirCoil

Suction

Coax

Discharge

Cooling

Mode


F


F

Discharge Line

psi

(saturation)

F

Suction Line

psi

(saturation)

F

Suction temp

F




Load

Coax

AirCoil

TXV

Filter Drier

Reversing

Valve

Source

Coax



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


24/24

P.O. Box 245

Syracuse, NY 13211

888-266-7684 US

800-969-7684 CAN

866-462-2914 FAX

www.roth-america.com

[email protected]

*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

*

*****

Documents

Heat Pumps Refrigeration Troubleshooting Manual