Troubleshooting Guide -
Tranquility
®
Digital (DXM2) Packaged Units
Rev.: 01/15/14
26
Geothermal Heat Pump Systems
Refrigeration Troubleshooting
A-H
Measuring Superheat and Subcooling
Superheat and subcooling are a good indication of refrigeration effi ciency. However, water and air measurements should
always be checked fi rst. Reference Figure 1a & 1b.
To Check SuperHeat and SubCooling
Determining Superheat:
1. Measure the temperature of the suction line at a point near the expansion valve bulb.
2. Determine the suction pressure in the suction line by attaching refrigeration gauges to the schrader connection on the side
of the compressor.
3. Convert the pressure obtained in Step 2 above to the boiling point (sat temp) temperature by using the Press/Temp
conversion table or the gauge set .
4. Subtract the temperature obtained in Step 3 from Step 1. The difference will be the superheat of the unit or the total
number of degrees above the boiling point. Refer to the superheat Table 1 for superheat ranges at specifi c entering water
conditions.
Example:
The temperature of the suction line at the sensing bulb is read at 59°F. The suction pressure at compressor is 135 psig which
is the equivalent to 47°F saturation temperature from HFC-410A Press/Temp conversion table on the gauge set.
47°F subtracted from 59°F = 12°F Superheat
Measuring Superheat
Compressor
Expansion
Device
Coax
HWG
RV
Air
Coil
Suction
Discharge
Heating Cycle
Digital
Thermometer
Superheat = Suction Line Temperature - Suction Saturation Temperature
Verify that HWG
is turned off
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