Reznor PDH Operation Manual PreevA - Manual (Page 26)

Form O-PreevA, Page 26
3.7 Optional
Cooling Coil
Module (cont’d)
Reheat Module Compressor Maintenance and Replacement (cont’d) 3.0 Maintenance
Procedures
(cont’d)
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Step 11. Check Circuit Subcooling and Superheat of Reheat
Circuit
PREPARATION:
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To verify superheat and subcooling, outdoor temperature must be between
70-95°F (21-35°C). If temperature is not within this range, consult the factory
service department before charging.
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Operate for 30 minutes for system to stabilize.
Check SUBCOOLING of the Reheat Circuit - Measure and record temperature
and pressure of the liquid line at the condenser coil outlet in the reheat circuit.
STEP 1) Record Measurements: Temperature =
________°F (°C) and Pressure = ________ psig
STEP 2) From Temperature/Pressure Conversion Chart,
APPENDIX, page 38, convert Measured Pressure (STEP 1) to
________°F (°C)
STEP 3) Subtract Measured Temperature (STEP 1) from Temperature
from Conversion Chart (STEP 2)
________°F (°C) - ________°F (°C) = ________°F (°C) degrees
of Subcooling
Recommended reheat circuit subcooling with outdoor temperature
range of 70-95°F (21-35°C) is 14-18°F (7.8-10°C).
Too much subcooling indicates a refrigerant overcharge. To reduce the
subcooling, remove excess refrigerant. Too little subcooling indicates a refrigerant
undercharge. To increase subcooling, slowly add R410A refrigerant.
WARNING
Do not release refrigerant to the atmosphere. When adding or
removing refrigerant, the qualified technician must comply
with all national, state/province, and local laws.
Determine SUPERHEAT of the Reheat Circuit - Measure and record temperature
(insulate probe from surrounding air temperature) and pressure in the suction line
at the compressor inlet of the reheat circuit.
STEP 1) Record Measurements: Temperature =
_______°F (°C) and Pressure = _______ psig
STEP 2) From Temperature/Pressure Conversion Chart,
APPENDIX, page 38, convert Measured Pressure (STEP 1) to
________°F (°C)
STEP 3) Subtract Measured Temperature (STEP 1) from
Temperature from Conversion Table (STEP 2)
________°F (°C) - ________°F (°C) = ________°F (°C) degrees
of Superheat
Recommended reheat circuit superheat at is 8-12°F (4.5-6.7°C).
Typically, too much superheat indicates that the evaporator coil is undercharged.
Too little superheat typically indicates that the evaporator coil is overcharged and
may potentially flood liquid refrigerant to the compressor. To reduce the superheat,
adjust the thermal expansion valve by turning the adjusting stem counterclock-
wise. To increase the superheat, adjust the thermal expansion valve by turning the
adjusting stem clockwise.
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Step 12. (Select the procedure that applies.)
IF the oil measured in Step 2 was significantly less than in the table on
page 21 or the acid test in Step 2 indicated a burnout, do the following:
a) Operate the unit for several hours. Check the pressure drop through the
3.7.4 Optional Reheat
Module (cont’d)