SUCTION GAS THERMISTOR — The thermistors that were
wired into the control box must now be installed on each
compressor.
024-030 Units — Install the marked thermistor onto com-
pressor no. 1 (the compressor on the left when viewing both
compressors from the compressor section door). To do so:
1. Lay the thermistor flat and in parallel with the suction
line between the compressor suction flange and the first
bend in the line (See Fig. 13).
2. Use a wire tie to secure the thermistor to the suction line.
3. Use an insulating compound (such as Press-Tite or simi-
lar) to completely surround the stainless steel probe. This
will improve the accuracy of the suction superheat
reading.
4. Follow the procedures in Steps 1-3 above to install the
unmarked thermistor onto the suction line of compressor
no. 2 (the compressor on the right when viewing both
compressors from the compressor section door).
034-074 Units — Compressor no. 1 is located on the left (when
viewing the compressors from the control box end of the
unit).
1. Remove the suction valve stem cap and fully backseat
the valve.
2. Remove the plug fitting threaded into the valve body.
3. Using a suitable thread sealant, install a compression fit-
ting (provided) into the valve body of compressor no. 1
and tighten (See Fig. 14-16).
4. Loosen the compression nut from the fitting and slide the
marked thermistor probe into the compression fitting body
(through the nut).
5. Push the thermistor probe into the compression fitting body
until it touches the valve stem.
6. Back the thermistor out slightly, snug compressor nut by
hand, and tighten
3
⁄
4
to 1 full turn with a wrench to ensure
a tight seal. DO NOT OVERTIGHTEN.
7. Turn the valve stem 1 to 1
1
⁄
2
full turns clockwise. Check
compression fitting seal for leaks, and tighten nut if
necessary.
8. Replace the valve stem cap.
9. Follow the procedures in Steps 1-8 above to install the
unmarked thermistor into the suction line valve of com-
pressor no. 2 (the compressor on the right when viewing
the compressors from the control box end of the unit).
Compressor System Pressure Check —
Use the
accessory HSIO keypad and display module (see Fig. 9) to
perform the following:
HSIO ENTRY
KEYPAD
DISPLAY
READING NAME
(EXPECTED DISPLAY)
TEMPS
System temperatures
SCTA X
Saturated condensing temperature,
circuit A (Near outdoor ambient)
STA X
Suction temperature, circuit A (Near
outdoor ambient)
SSTA X
Saturated suction temperature, circuit
A (Near outdoor ambient)
SHA X
Superheat, circuit A (STA-SSTA)
SCTB X
Saturated condensing temperature,
circuit B (Near outdoor ambient)
STB X
Suction temperature, circuit B (Near
outdoor ambient)
SSTB X
Saturated suction temperature,
circuit B (Near outdoor ambient)
SHB X
Superheat, circuit B (STB-SSTB)
HSIO ENTRY
KEYPAD
DISPLAY
READING NAME
(EXPECTED DISPLAY)
PRESSURE System pressures
DPA X
Discharge pressure, circuit A (100
to 170 psig*)
SPA X
Suction pressure, circuit A (100 to
170 psig*)
DPB X
Discharge pressure, circuit B (100
to 170 psig*)
SPB X
Suction pressure, circuit B (100 to
170 psig*)
*Actual pressure readings will vary with outdoor ambient tempera-
tures. Refer to an R-22 Temperature/Pressure Chart for approxi-
mate gage pressure at current outdoor ambient temperature.
If the pressure displayed varies outside of the acceptable
table listed above, refer to Pressure Troubleshooting table
on page 15 for possible causes.
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