roth heat pump refrigeration troubleshooting manual

P.O. Box 245Syracuse, NY 13211

www.roth-america.com888-266-7684

Refrigeration/Troubleshooting Manual

Table of Contents:

Section 1: Geothermal Refrigeration CircuitsOverview ................................................................ 2Water-to-Air Refrigerant Circuit ........................... 3Refrig. Ckt. Component Operation .................... 3Water-to-Water Refrigerant Circuit ..................... 5Heating Operation ................................................ 6Cooling Operation ................................................ 6Summary ................................................................ 8

Section 2: Heat of Extraction/Heat of RejectionOverview ................................................................ 9Performance Data ................................................ 9Formulas ............................................................... 10Examples .............................................................. 12

Section 3: Superheat/SubcoolingOverview .............................................................. 14Definitions ............................................................. 14Checking Superheat and Subcooling .............. 14Putting It All Together .......................................... 15Pressure/Temperature Chart R-410A ................ 16Pressure/Temperature Chart R-22 ..................... 17Superheat/Subcooling Measurements ............ 18Superheat/Subcooling Tables ........................... 19Examples .............................................................. 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

2Roth Refrigeration/Troubleshooting Guide,August, 2010

exchanger (water-to-water and water-to-air units) is connected to the ground loop or open loop (well water) system. The “load” heat exchanger is connected to the hydronic load (for example, radiant floor heating) for water-to-water units. The load heat exchanger in a water-to-air unit is the air coil, which is connected to duct work.

Overview

Geothermal heat pumps are available in a variety of configurations to provide flexibility for installation in new construction or retrofit applications. Most common in North America are packaged water-to-air heat pumps, which provide forced air heating and cooling. Packaged units (see figure 1) have the compressor section and the air handler section in the same cabinet. There are also other types of geothermal heat pumps, such as water-to-water, which are used for radiant floor heating.

Water-to-water heat pumps heat or chill water instead of heating or cooling the air (see figure 5). The difference between a water-to-air and water-to-water heat pump is the “load” heat exchanger. A second water-to-refrigerant coil is substituted for the 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

Air

Co

il

Suct

ion

Co

ax

Discharge

HeatingMode

Air

Co

il

Suct

ion

Co

ax

Discharge

CoolingMode

Liquid line (heating)Liquid line (cooling)

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax

Optional desuperheaterinstalled in discharge line(always disconnect during

troubleshooting)

Condenser (heating)Evaporator (cooling)

Condenser (cooling)Evaporator (heating)

Suction

Discharge

13

2 4

5 6

3Refrigeration/Troubleshooting GuideAugust, 2010

Roth

Water-to-Air Refrigerant Circuit

The water-to-air geothermal heat pump refrigerant circuit is very simple compared to air source heat pumps. Defrost cycle is not required, and all components are indoors in a single cabinet. The main components shown in figure 1 are the compressor (1), the air coil (2), the coaxial heat exchanger (3), the reversing valve (4), the TXV or thermal expansion valve (5), and the filter drier (6).

Compressor: The compressor (1) is the “heart” of the system. The compressor pumps refrigerant through the circuit, and increases the pressure of the refrigerant. Since pressure and temperature are directly related, when the pressure is increased, the temperature is also increased. When the temperature of the refrigerant is raised to a higher temperature than the temperature of the air flowing through the air coil (2) in heating, heat is released to the air to heat the building. Likewise, when the refrigerant temperature is raised to a higher temperature than the water flowing through the coaxial heat exchanger (3) in cooling, heat is released to the water.


Roth uses Copeland Scroll compressors. A scroll is an involute spiral which, when matched with a mating spiral scroll form as shown in figure 2, generates a series of crescent-shaped gas pockets between the two members. Scroll compressors work by moving one spiral element inside another stationary spiral to create a series of gas pockets that become smaller and increase the pressure of the gas.

The largest openings are at the outside of the scroll where the gas enters on the suction side. As these gas pockets are closed off by the moving spiral they move towards the center of the spirals and become smaller and smaller. This increases the pressure on the gas until it reaches the center of the spiral and is discharged through a port near the center of the scroll. Both the suction process (outer portion of the scroll members) and the discharge process (inner portion) are continuous.

The moving scroll moves in an orbiting path within the stationary (fixed) scroll as it creates the series of gas pockets. During compression, several pockets are being compressed simultaneously, resulting in

Figure 2: Scroll Operation

1

2

3

4

5

1

2

3

4

5

1

2

3

4

5

1

2

3

4

5

1

2

3

4

5Compression 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.



a very smooth process. By maintaining an even number (six in a Copeland Scroll compressor) of balanced gas pockets on opposite sides, the compression forces inside the scroll work to balance each other and reduce vibration inside the compressor.

Single speed and two-stage (UltraTech) scroll compressors are used in Roth’s product line. The two-stage scroll works exactly like the single speed scroll shown in figure 2, but it has additional components, a solenoid valve, and bypass ports in the scroll mechanism. When the solenoid valve opens the bypass ports as shown in figure 3, the capacity is reduced to 67%, since part of the scroll is bypassed.

67% - Ports oPen 100% Ports Closed

Figure 3: UltraTech Operation

Air Coil: The air coil (2), a refrigerant-to-air heat exchanger servers as the condenser in heating, and the evaporator in cooling.

Coaxial Heat Exchanger: The coaxial heat exchanger (3), a water-to-refrigerant heat exchanger, serves as the evaporator in heating, and the condenser in cooling.

Reversing Valve: The reversing valve (4) provides the ability to switch functions of the two heat exchangers, above. As shown in figure 1, the discharge line from the compressor is always connected to the bottom of the reversing valve. The center connection at the top is always connected to 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 is heating. Therefore, the discharge gas from the compressor flows to the air coil in the non-energized mode. When the reversing valve solenoid is energized in cooling, the valve switches to allow the discharge gas from the compressor to flow to the coaxial heat exchanger.

The reversing valve is a pilot-operated valve, which means that the solenoid opens a small port, connecting the copper tubing from the bottom port (discharge line from the compressor) to the valve chamber. The high pressure of the discharge 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 the proper amount of refrigerant is being fed to the heat exchangers in order to maximize the condensing and evaporating functions. The TXV is also important in keeping liquid refrigerant from reaching the suction line of the compressor, which could damage the compressor. The TXV is designed to operate bi-directionally in packaged water-to-air and water-to-water heat pumps.

Diaphram

Valve Seat

Pin

4

4 = Liquid Pressure (opening force)

Figure 4: TXV Operation


Roth


Figure 4 shows the operation of the TXV, and the four forces that affect the operation. The TXV has two copper fittings for connection to the air coil and coaxial heat exchanger, as well as two smaller copper lines that are used for metering. One line is connected to a bulb that is attached to the suction line of the compressor. The bulb is filled with refrigerant. As the suction line temperature changes, the bulb pressure changes. The other line is connected directly to the suction line. The bulb pressure (force 1) pushes down on the diaphragm as the bulb pressure increases (suction line temperature increases). When the pressure pushes down on the diaphragm, the pin (which is attached to the diaphragm) is pushed away from the valve seat, which opens the valve.

The other line, connected directly to the suction line uses suction pressure (force 2) to push up on the diaphragm as the pressure increases. As the diaphragm is pushed up, the pin is pushed into the valve seat, closing


To suction line

Load

Co

ax

Suct

ion

Sou

rce

Co

ax

Discharge

HeatingMode

Load

Co

ax

Suct

ion

Sou

rce

Co

ax

Discharge

CoolingMode


LoadCoax

TXV

Filter Drier

ReversingValve

SourceCoax


troubleshooting)



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 causes the valve to meter at 0°F superheat (see section 3 for explanation of superheat). Since it is important to make sure that liquid is not returning to the compressor, the valve spring (force 3) is adjusted to “fool” the valve into balancing at a higher superheat (usually 10 to 12°F). Force 4 (liquid pressure) is an opening force.

Filter Drier: The filter drier (6) functions exactly as its name implies. It filters any particles from the refrigerant system, and it pulls moisture from the system. It is extremely important that the filter drier is changed any time the refrigerant circuit is open for a component replacement or repair, especially for systems with R-410A refrigerant. R-410A uses P.O.E. oil, which is hygroscopic (tendency of a material to absorb moisture from the air). Moisture contaminates the refrigerant circuit over time, and must be avoided.



Water-to-Water Refrigerant Circuit

The water-to-water heat pump refrigerant circuit, as shown in figure 5, functions exactly the same as the the water-to-air refrigerant circuit with one exception. The air coil is replaced by a second coaxial heat exchanger. The source coax is the 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 refrigerant circuit operation in heating and cooling modes, the water-to-air circuit will be used. The other configurations directly apply with minor terminology/component changes.

In heating mode (see figure 7), the reversing valve is not energized. The high temperature, high pressure refrigerant gas from the compressor flows to the air coil. As the air moves through the air coil, the cool (typically 70°F) air causes the hot refrigerant (typically 130 to 180°F) to condense into a liquid. Thus, the air coil is the condenser in the heating mode.

After leaving the air coil (condenser), the refrigerant is approximately the temperature of the leaving air. The refrigerant is within a few psi of being at the same pressure as it was at the compressor discharge line. This is the heating liquid line. The liquid line of a packaged unit changes location, depending upon the mode of operation. It is always located between the 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 through a very small opening, which causes a large pressure drop. As mentioned earlier,

pressure and temperature are directly related, so the temperature also drops after the TXV. At this point, the refrigerant is a low temperature liquid (typically 15 to 50°F, depending upon loop temperature).

The warm water (or water/antifreeze solution) flowing through the coaxial heat exchanger (typically 30 to 60°F) causes the cold refrigerant to “boil” off (evaporate) into a gas or vapor. Thus, the coax is the evaporator in heating.

After leaving the coax (evaporator), the refrigerant is now approximately the same temperature as the water entering the heat pump. This low pressure gas enters the compressor, and the cycle starts all over again.

Proper refrigerant metering will insure that no liquid is returned to the compressor. Section 3 discusses superheat and subcooling, which allow the technician to evaluate how well the condenser and evaporator are operating.

Cooling Operation

In cooling mode (see figure 8), the reversing valve must be energized. The high temperature, high pressure refrigerant gas from the compressor flows to the coaxial heat exchanger. As the water (or water/antifreeze solution) flows through the coax, the cool (typically 50 to 100°F) water causes the hot refrigerant (typically 130 to 180°F) to condense into a liquid. Thus, the coax is the condenser in the cooling mode.

After leaving the coax (condenser), the refrigerant is approximately the temperature of the water leaving the coax. The refrigerant is within a few psi of the compressor discharge line pressure. This is the cooling liquid line. The liquid line of a packaged unit changes location,


Roth



To suction line


Air

Co

ilTXV

Filter Drier

ReversingValve

SourceCoax


troubleshooting)



Suction

Discharge

Figure 7: Heating Mode

Figure 8: Cooling Mode


To suction line


Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


troubleshooting)



Suction

Discharge



depending upon the mode of operation. It is always located between the 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 through a very small opening, which causes a large pressure drop. Once again, since pressure and temperature are directly related, the temperature also drops after the TXV. At this point, the refrigerant is a low temperature liquid (typically 35 to 45°F, depending upon return air temperature and air flow).

The warm air flowing through the air coil (typically 70 to 80°F) causes the cold refrigerant to “boil” off (evaporate) into a gas or vapor. Thus, the air coil is the evaporator in cooling.

After leaving the air coil (evaporator), the refrigerant is now approximately the same temperature as the air entering the heat pump. This low pressure gas enters the compressor, and the cycle starts all over again.

Summary

To summarize, refrigerant circuits in geothermal heat pumps can be configured for packaged water-to-air, water-to-water, split systems or combination water-to-air and water-to-water units. All circuits utilize a Copeland scroll (single or two-stage) compressor, one or two water-to-refrigerant coaxial coils, an air-to-refrigerant coil, a reversing valve, a bi-directional TXV, and a filter drier. Combination units include a direction valve and a 3-way valve to switch condenser operation.

The air coil operates as the condenser in heating, 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 second coax instead of the air coil.

The reversing valve is energized in the cooling mode. The non-energized mode is heating.


Roth

Section 2: Heat of Extraction/Heat of Rejection

Overview

As mentioned in section 1, most geothermal heat pumps are packaged water-to-air heat pumps. Therefore, the refrigerant circuit is evacuated and charged at the factory, and there is no need to connect refrigerant gauges unless the technician has verified that there is a refrigerant circuit problem. Since connecting gauges can cause a loss of charge and affect performance, Roth recommends against connecting refrigerant gauges at startup. There are a number of checks that can be made at startup to verify performance without connecting refrigerant gauges.

Heat of extraction is a calculation of the amount of heat that is being “extracted” or “absorbed” from the water or water/anti-freeze solution by the evaporator (coaxial heat exchanger) in the heating mode. Heat of rejection is the amount of heat that is being “rejected” to the water by the condenser (coaxial heat exchanger) in the cooling mode. In addition to measuring the temperature rise or drop across the air coil, calculating heat of extraction or heat of rejection allows the technician to verify that the heat pump is performing according to specifications. If the calculation shows that the heat pump is performing poorly, then refrigeration gauges may be required to further troubleshoot the problem.

Performance Data

Before discussing heat of extraction (HE) / heat of rejection (HR) calculations, the technician should understand how to use the performance data in the catalog to compare the unit specifications to actual calculations.

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 figure 9, HE is the amount of heat that is being extracted from the water (for example, ground loop) by the refrigerant circuit. The compressor and fan power (kW column) is used to operate the refrigerant circuit. The heat delivered to the space (HC column) equals the HE from the water plus the waste heat of 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 figure 9, at 30°F EWT, 9.0 GPM and 70°F EAT, the heating capacity is 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 specifications. There is no need to connect refrigerant gauges if HE is within specifications.

In figure 10, HR is the amount of heat that is being rejected to the water (for example, ground loop) by the refrigerant circuit. The compressor and fan power (kW column) is used 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 of the power used for compressor and fan. If the kW is converted to Btuh, and added to the TC, the sum should equal HR.

For example, in figure 10, at 90°F EWT, 9.0 GPM and 75°F DB/63°F WB (50% RH), HR is 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 to TC, the result is HR. Thefore, if HR is within, 10-15% of catalog performance, TC should also be within specifications. There is no need to connect refrigerant gauges if HR is within specifications.


Formulas

The formula is the same for HE and HR. The amount of heat being extracted or rejected can be calculated if the temperature difference between water entering and leaving the coaxial heat exchanger (TD) is known, and the water flow (GPM) is measured. The only other item needed is the type of antifreeze. A fluid factor is used to represent the specific heat of the water/antifreeze solution, as well as to 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 for most antifreezes Figures 11 and 12 show the tools required for checking HE and HR. All technicians installing and servicing geothermal heat pumps should have at least one set of these tools.

Flow rate can be determined by measuring the pressure drop across the coaxial heat exchanger. The pressure gauge and adapter should be inserted into the P/T (pressure/temperature) port of the “Water IN” connection. Record the reading. Next, insert the gauge into the “Water OUT” port, and record the reading. The difference between the “IN” and “OUT” is the pressure drop.

Once the pressure drop of the heat exchanger is known, the flow rate can be determined by consulting the performance data for the particular unit.

Example:

In heating mode, model 036 has EWT of 50°F, water pressure “IN” of 40 psi, and water pressure “OUT” of 35 psi. The pressure drop, therefore is 5 psi. Figure 10 shows three

water pressure drop values and three water flow rates. At 50°F, if the pressure drop is 1.7 psi, the flow rate would be 5.0 GPM; if the pressure drop is 3.1 psi, the flow rate would be 7.0 GPM; and if the pressure drop is 5.0 psi, the flow rate would be 9.0 GPM. The flow rate in this example is 9.0 GPM. Rarely are the temperature and pressure drop exactly as shown in the tables, so there will be some interpolation required (for example, 52°F EWT and 4.7 psi pressure drop).

NOTE: A large gauge face is preferred, since it will be easier to read pressures to the nearest 0.5 psi. ALWAYS use the same gauge in the “IN” and “OUT” connections. The use of two gauges could cause false readings, since they could both be out of calibration in opposite directions. Never force the gauge adapter into the P/T port. The gauge adapter could break off in the P/T port, or the force could cause the ring holding the P/T port bladder to become dislodged, potentially ending up in a pump impeller.

Once the flow rate is determined, the pocket thermometer can be used to obtain TD. Insert the thermometer into the “Water IN” P/T port. Record the temperature. Insert the thermometer into the “Water OUT” port, and record the temperature. The difference between the “IN” and “OUT” is the TD. In heating, EWT (entering water temperature) will be warmer than LWT (leaving water temperature); in cooling it will be just the opposite.

The last item needed is the type of fluid circulating through the heat pump. As mentioned earlier, 500 should be used for pure water (open loop/well water systems). Use 485 for most antifreeze solutions (see Flow Center and Loop Application Manual for details on antifreeze solutions).


Roth


036 Performance Data:3.0 Ton, 1200 CFM, Heating

EWT GPMretaehrepuseD htiw gnitaeHgnitaeHDPW

PSI FT EAT HC HE LAT KW COP HC HE LAT KW DH COP

30

5.0 1.8 4.260 30.2 21.7 83.3 2.47 3.58 26.5 21.7 80.4 2.45 3.8 3.6270 29.4 20.4 92.7 2.61 3.30 25.5 20.5 89.7 2.56 3.9 3.3680 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 7.860 31.1 22.6 84.0 2.50 3.65 27.3 22.7 81.0 2.45 3.9 3.7370 30.3 21.3 93.4 2.63 3.37 26.3 21.4 90.3 2.58 4.0 3.4480 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 12.560 31.5 23.0 84.3 2.50 3.70 27.6 23.2 81.3 2.44 3.9 3.7870 30.7 21.8 93.7 2.63 3.42 26.6 18.7 90.6 2.58 4.1 3.4980 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 3.960 39.1 30.3 90.2 2.59 4.42 34.2 30.6 86.4 2.51 4.9 4.5770 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 7.260 40.7 31.7 91.4 2.64 4.52 35.7 32.1 87.5 2.56 5.1 4.6770 39.4 30.0 100.4 2.78 4.15 34.2 30.2 96.4 2.69 5.2 4.2980 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 11.660 41.6 32.6 92.1 2.65 4.59 36.4 32.8 88.1 2.56 5.2 4.7670 40.2 30.7 101.1 2.79 4.22 34.9 31.1 96.9 2.70 5.3 4.3680 38.9 28.9 110 2.94 3.88 33.4 29.2 105.8 2.84 5.5 4.01

EnteringWater

Temp (°F)

FlowRate

(U.S. GPM)

Water Press. Drop

(PSI & Ft. of Head)

EnteringAir

Temp (°F)

HeatingCapacity(MBtuh)

Heat ofExtraction

(MBtuh)

LeavingAir

Temp (°F)

InputPower (kW)

Coefficientof

Performance

DesuperheaterCapacity(MBtuh)

Figure 9: Typical Performance Data - Heating Mode

036 Performance Data:3.0 Ton, 1200 CFM, Cooling

EWT GPMWPD EAT

DB/WB

retaehrepuseD htiw gnilooCgnilooC

PSI FT TC SC HR KW EER TC SC HR KW DH EER

70

5.0 1.7 3.975/63 36.7 26.8 44.8 2.41 15.2 36.9 26.9 44.9 2.35 4.7 15.780/67 39.8 27.9 47.6 2.47 16.1 40.0 28.0 47.7 2.40 4.9 16.785/71 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 6.975/63 37.2 27.1 45.0 2.29 16.2 37.4 27.2 45.1 2.26 4.6 16.680/67 40.5 28.2 47.9 2.34 17.3 40.4 28.3 48.0 2.31 4.7 17.685/71 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 11.175/63 37.6 27.1 45.2 2.22 16.9 37.8 27.2 45.4 2.21 4.3 17.180/67 40.9 28.2 48.1 2.27 18.0 41.1 28.3 48.3 2.26 4.5 18.285/71 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 3.675/63 33.4 25.7 43.1 2.98 11.2 33.7 25.9 43.3 2.89 6.3 11.780/67 36.3 26.8 45.9 3.04 11.9 36.6 27.0 46.0 2.95 6.4 12.485/71 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 6.475/63 34.0 26.0 43.4 2.81 12.1 34.3 26.2 43.6 2.75 6.0 12.580/67 37.0 27.1 46.1 2.87 12.9 37.3 27.2 46.3 2.80 6.2 13.385/71 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 10.375/63 34.4 26.0 43.4 2.73 12.6 34.7 26.2 43.8 2.70 5.8 12.980/67 37.4 27.1 46.2 2.78 13.4 37.8 27.2 46.6 2.75 5.9 13.785/71 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 ofRejection(MBtuh)

InputPower (kW)

EnergyEfficiency

Ratio

Figure 10: Typical Performance Data - Cooling Mode


Section 2: Heat of Extraction/Heat of RejectionFigure 13 includes an example water-to-air heat pump in heating mode; figure 14 shows the same heat pump in cooling. Following are two examples based upon these figures, which are shown on the next page.

Example 1: Model 036, ground loop system with ProCool (ethanol) antifreeze solution, heating mode.

1) Fluid factor = 4852) EWT = 30.0°F LWT = 23.5°F TD = 6.5°F3) 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

Pressure Gauge(P/N TSPG-GC or equivalent)

Gauge Adapter(P/N TSPTN) Adapter

Protector

Pocket ThermometerP/N TSDT or equivalent

Figure 11: Pressure Gauge with Adapter

performing better than specifications.

Example 2: Model 036, ground loop system with ProCool (ethanol) antifreeze solution, cooling mode.

1) Fluid factor = 4852) EWT = 90.0°F LWT = 101.2°F TD = 11.2°F3) 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 is performing better than specifications.

NOTE: HE and HR should be within 10-15% of catalog values.

Figure 12: Pocket Thermometer


Roth



To suction line

Air

Co

il

Suct

ion

Co

ax

Discharge

HeatingMode

Air

Co

il

Suct

ion

Co

ax

Discharge

CoolingMode

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

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


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

101.2

36.3

90.0

40.075.0 55.0


To suction line

Air

Co

il

Suct

ion

Co

ax

Discharge

HeatingMode

Air

Co

il

Suct

ion

Co

ax

Discharge

CoolingMode


°F


°F

Discharge Line

psi(saturation)

°F

Suction Line

psi(saturation)

°F

Suction temp°F



LoadCoax

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


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

23.5

36.6

30.0

40.070.0 93.4

Figure 13: Heating Operation Example

Figure 14: Cooling Operation Example


Section 3: Superheat/Subcooling Overview

Superheat and subcooling are used to determine if the heat pump has the proper refrigerant charge, as well as for verifying that the condenser and evaporator are performing properly. Superheat and subcooling can even be used to troubleshoot refrigerant circuit blockages or a bad TXV.

Definitions

Saturation Temperature: Saturation temperature, sometimes called boiling point, is the temperature at which a refrigerant changes state. For example, Table 1 shows that refrigerant R-410A has a saturation temperature of 32°F at 100 psi. Therefore, the refrigerant at 100 psi is a liquid if it is below 32°F, and a gas (vapor) if it is above 32°F.

Superheat: Superheat is defined as the number of degrees above the saturation temperature of a refrigerant. For example, if the temperature of refrigerant R-410A is 40°F at 100 psi, it has 8°F of superheat, since the saturation temperature is 32°F.

Subcooling: Subcooling is defined as the number of degrees below the saturation temperature of a refrigerant. For example, if the temperature of refrigerant R-410A is 28°F at 100 psi, it has 4°F of subcooling, since the saturation temperature is 32°F.

Checking Superheat and Subcooling

Superheat and subcooling should only be checked after the heat of extraction or heat of rejection calculations (see section 2) indicate that the unit is performing poorly. Connecting refrigerant gauges should be done as a last resort.

Checking superheat and subcooling requires a refrigeration gauge set with manifold and hoses, plus a digital thermocouple type thermometer. Heat pumps produced by Roth have two schrader ports for service connections, one at the discharge line of the compressor, and one at the suction line of the compressor. When these pressures are used in conjunction with the suction line temperature and liquid line temperature, superheat and subcooling can be calculated. Insulation should be removed from the suction line and liquid line, and the copper should be free from insulation glue, so that the thermocouple makes a good connection at the copper line.

Figures 15a and 15b illustrate the locations for taking pressure and temperature measurements. Notice that the two areas for temperature measurement are suction line and liquid line. In order to check superheat and subcooling, the saturation temperature must be determined, which requires the pressure of the refrigerant and the actual temperature of the refrigerant at the same location. However, the only location where both temperature and pressure are easily obtained is at the suction line. In section 1, temperatures and pressures were discussed in relation to components, both before and after the components. It was also mentioned that the discharge pressure and the liquid line pressure are within a few psi of each other. Most manufacturers of packaged equipment adjust their service data to allow the technician to use the discharge pressure as the liquid line pressure. Therefore, for checking superheat and subcooling, use discharge pressure with liquid line temperature, and suction pressure with suction temperature.

Although superheat and subcooling can be calculated anywhere in the refrigeration


Roth

Section 3: Superheat/Subcoolingcircuit, there are two points that are most useful for troubleshooting purposes. First of all, it is imperative that liquid is not returned to the compressor. Liquid refrigerant will “wash” some of the compressor oil away from critical internal parts, causing premature compressor failure. Plus, the compressor is designed to pump gas, not liquid, and will be operating under adverse conditions. Checking for superheat at the suction line of the compressor insures that the state of the refrigerant at this point is a gas (vapor). The amount of superheat at the suction line determines how well the evaporator (coax in heating, air coil in cooling) is working. Superheat is normally in the 8 to 12°F range, but the installation manual will provide specific information for the unit being serviced. NOTE: Check the temperature of the suction line near the TXV bulb, especially on split systems.

The other location to check is the liquid line. Since the liquid line is located after the condenser (air coil in heating, coax in heating), the amount of subcooling determines how well the condenser is working. In most cases subcooling is in the 4 to 10°F range, but the installation manual will provide specific information for the unit being serviced.

Putting It All Together

In section 1, TXV operation was discussed. Since the TXV spring has been adjusted to maintain 8 to 12°F of superheat, it will close down when necessary to maintain the predetermined superheat setting. Therefore, subcooling plays a crucial part in evaluating the unit’s refrigeration charge. In other words, if the unit is overcharged, the TXV will close down to maintain superheat, backing up liquid refrigerant in the condenser. 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 there is a problem with the refrigeration charge. Table 3 lists the conditions associated with high or low superheat and subcooling. Table 4 is an example of typical data found in the installation manual.

Figures 16 through 18 illustrate examples of a normally charged system, an undercharged system, and an overcharged system.


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 53 395 116

12 -39 155 55 400 117

14 -36 160 57 405 118

16 -33 165 59 410 119

18 -30 170 60 415 120

20 -28 175 62 420 121

22 -26 180 64 425 122

24 -24 185 66 430 122

26 -20 190 67 435 123

28 -18 195 69 440 124

30 -16 200 70 445 125

32 -14 205 72 450 126

34 -12 210 73 455 127

36 -10 215 75 460 128

38 -8 220 76 465 129

40 -6 225 78 470 130

42 -4 230 79 475 130

44 -3 235 80 480 131

46 -2 240 82 485 132

48 0 245 83 490 133

50 1 250 84 495 134

52 3 255 85 500 134

54 4 260 87 505 135

56 6 265 88 510 136

58 7 270 89 515 137

60 8 275 90 520 138

62 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 96 545 142

72 16 305 97 550 142

74 17 310 98 555 143

76 19 315 99 560 144

78 20 320 100 565 145

80 21 325 101 570 146

85 24 330 102 575 146

90 26 335 104 580 147

95 29 340 105 585 148

100 32 345 106 590 149

105 34 350 108 595 149

110 36 355 108 600 149

115 39 360 109 650 154

120 41 365 110 700 159

Table 1: Pressure/Temperature Chart, R-410A Refrigerant


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 67 325 137

12 -17 120 69 330 138

14 -14 125 72 335 140

16 -11 130 74 340 141

18 -8 135 76 345 142

20 -5 140 78 350 144

22 -3 145 81 355 144

24 0 150 83 360 145

26 2 155 85 365 146

28 5 160 87 370 147

30 7 165 89 375 148

32 9 170 91 380 149

34 11 175 93 385 151

36 13 180 94 390 152

38 15 185 96 395 153

40 17 190 98 400 155

42 19 195 100 405 155

44 21 200 101 410 156

46 23 205 103 415 158

48 24 210 105 420 159

50 26 215 107 425 160

52 28 220 108 430 160

54 29 225 110 435 161

56 31 230 112 440 162

58 32 235 113 445 163

60 34 240 115 450 164

62 35 245 116 455 165

64 37 250 118 460 167

66 38 255 119 465 168

68 40 260 120 470 169

70 41 265 121 475 169

72 42 270 123 480 170

74 44 275 124 485 171

76 45 280 126 490 172

78 46 285 127 495 173

80 48 290 129 500 173

85 51 295 130

Table 2: Pressure/Temperature Chart, R-22 Refrigerant



°F


To suction line


°F


°F

Discharge Line

psi(saturation)

Suction Line

psi(saturation)

°F

Suction temp°F



LoadCoax

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


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

R-410A Manifold/Gauge Set

Suction Discharge

°FThermometer

1

2

21


To suction line


°F


°F

Discharge Line

psi(saturation)

°F

Suction Line

psi(saturation)

°F

Suction temp°F



LoadCoax

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


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

R-410A Manifold/Gauge Set

Suction Discharge

°FThermometer

1

2

21

Figure 15a: Superheat/Subcooling Measurement - Heating

Figure 15b: Superheat/Subcooling Measurement - Cooling


Roth

Superheat Subcooling Condition

Normal Normal Normal operation

Normal High Overcharged

High Low Undercharged

High High Restriction or TXV is stuck almost closed

Low 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)

30 1.5 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

70 1.5 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)

50 1.5 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

70 1.5 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 Figure 16: Normally-Charged System, Heating Mode

Figure 17: Under-Charged System, Heating Mode


To suction line

Air

Co

il

Suct

ion

Co

ax

Discharge

HeatingMode

Air

Co

il

Suct

ion

Co

ax

Discharge

CoolingMode


°F


°F

Discharge Line

psi(saturation)

°F

Suction Line

psi(saturation)

°F

Suction temp°F



LoadCoax

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


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

30.0

40.0

7.0

23.5

36.6

76 19

300

29

90.0

70.0

Superheat =29 - 19 = 10°F

Subcooling =96 - 90 = 6°F


To suction line

Air

Co

il

Suct

ion

Co

ax

Discharge

HeatingMode

Air

Co

il

Suct

ion

Co

ax

Discharge

CoolingMode


°F


°F

Discharge Line

psi(saturation)

°F

Suction Line

psi(saturation)

°F

Suction temp°F



LoadCoax

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


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

30.0

40.0

7.0

26.5

36.6

68 14

260 87

29

87.0

70.0 90.0




Roth

Section 3: Superheat/Subcooling Figure 18: Over-Charged System, Heating Mode


To suction line

Air

Co

il

Suct

ion

Co

ax

Discharge

HeatingMode

Air

Co

il

Suct

ion

Co

ax

Discharge

CoolingMode


°F


°F

Discharge Line

psi(saturation)

°F

Suction Line

psi(saturation)

°F

Suction temp°F



LoadCoax

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


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

30.0

40.0

26.5

36.6

85 24

325 101

34

85.0

70.0 90.0



Figure 19: Water-to-Air Refrigerant Circuit with Desuperheater


To suction line

Air

Co

il

Suct

ion

Co

ax

Discharge

HeatingMode

Air

Co

il

Suct

ion

Co

ax

Discharge

CoolingMode


°F


°F

Discharge Line

psi(saturation)

°F

Suction Line

psi(saturation)

°F

Suction temp°F



LoadCoax

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax

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

Desuperheater


Section 4: Desuperheater OperationThe desuperheater option includes a water-to-refrigerant coaxial heat exchanger installed between the compressor discharge line and reversing valve, which is connected to the condenser (air coil in heating, coax in cooling) as shown in figure 19. Unlike the source coax in all Roth geothermal heat pumps, the desuperheater coax is a double-wall, vented water-to-refrigeration heat exchanger. Figure 20 illustrates a cut-away of the desuperheater coax.

The operation of the desuperheater takes advantage of the superheat at the discharge line. For example, in figure 16, the discharge pressure is 300 psi. The saturation temperature at 300 psi is 96°F. The discharge line at these conditions would typically be around 160°F. Therefore, the superheat (actual temperature – saturation temperature) is 64°F. As domestic hot water flows through the desuperheater heat exchanger, some of the superheat at the discharge line is used to heat domestic water, which lowers the superheat at the discharge line, thus the term desuperheater.

Water flow rate through the desuperheater coax must be very low to avoid turning the desuperheater into a condensor, and “robbing” too much heat from the main condenser. Typically, about 0.4 GPM per ton is used for desuperheater flow rate. The desuperheater pump operates anytime the compressor is operating (unless the one of the temperature limits is open).

In cooling, the desuperheater takes some of the heat that would have been rejected to the ground loop via the condenser (coax), and uses it to make domestic hot water. Therefore, the desuperheater produces nearly free hot water (other than the fractional horsepower circulating pump) in the cooling mode.

In heating, the desuperheater takes some of the heat that would have been used to heat the space via the condenser (air coil), and uses it to make domestic hot water. Even though the desuperheater is “robbing” some of the heat from the space, it is a very small amount, and the system is heating water at a very high C.O.P. (3.0 to 4.0, depending upon loop temperature), compared to an electric water heater at a C.O.P. of 1.0.

Some geothermal heat pumps turn off the desuperheater pump when back up heat is energized. However, studies show that on an annual basis, the system is more energy efficient when the desuperheater is utilized any time the compressor is running. When the hot water tank is already heated, a thermal switch turns off the desuperheater pump. The pump may also be turned off if the compressor discharge line is too cool.

Figure 20: Desuperheater coax cut-awaySteel Outer Wall

Rifled Copper Tube

Smooth WallInner Tube

Refrigerant

Air Gap

Water


Roth

Troubleshooting FormPlease 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

Air

Co

il

Suct

ion

Co

ax

Discharge

HeatingMode

Air

Co

il

Suct

ion

Co

ax

Discharge

CoolingMode


°F


°F

Discharge Line

psi(saturation)

°F

Suction Line

psi(saturation)

°F

Suction temp°F



LoadCoax

Air

Co

il

TXV

Filter Drier

ReversingValve

SourceCoax


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 gauges until Heat of Extraction or Rejection has been checked.

Note: Disconnect desuperheater before proceeding

P.O. Box 245Syracuse, NY 13211

888-266-7684 US800-969-7684 CAN866-462-2914 FAX

[email protected]

* AHRI certification is shown as the Roth brand under the Enertech Manufacturing certification reference number**Roth Industries geothermal heat pumps are shown as a multiple listing of Enertech Manufacturing’s ETL certification*** Roth geothermal heat pumps are listed as a brand under Enertech Manufacturing’s Energy Star ratings

***

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roth heat pump refrigeration troubleshooting manual

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