Dectron, Inc. March 2012
DECTRON
DSH/DSV/RSH/DBH/RBH Series Dehumidifier Owner’s Manual
Data subject to change without notice.
308
Service Diagnostics - Mechanical
Problems not indicated by Supervisaire
®
Controller
SYMPTOM POSSIBLE CAUSES CHECKS & CORRECTIONS
Supply-air temperature
too low
Low compressor oil
pressure
Unit is in air-conditioning mode
• Check set points. Verify operating of air-
conditioning diverting valve--it may be
jammed:
1. Force the suspect valve to operate and
check for changes in operating temperatures
and pressures. If no changes occur, then
the valve is completely jammed and must
be replaced.
2. If the unit runs fine in A/C, trips on high
pressure in dehumidification mode, and
also runs with higher than normal pressures
in A/C alone, then the three-way valve is
not shifting completely out of air condition-
ing. (This is assuming that no other cause
for a high pressure trip can be found.
• Replace the defective valve.
Excessive outdoor-air intake
• Adjust outdoor intake rate to no more than
15% of the total airflow.
Compressor crankcase full of
liquid refrigerant
• Be sure the compressor crankcase heater is
warm. Allow at least 12 hours for it to heat
up before initial startup.
Expansion valve incorrectly
adjusted
• The compressor discharge temperature
must be in the correct range. See Startup
section.
There are only a limited number of ways in
which liquid refrigerant can return to the
compressor:
1. The return air is too cold and/or dry and
is not vaporizing the refrigerant in the
evaporator.
2. The thermal expansion valve is
misadjusted or defective and is not meter-
ing the refrigerant properly.
3. The pumpdown valve ( on units so
equipped) is leaking during the off cycle,
allowing the evaporator to accumulate
liquid. Oil failures caused by this problem
will only occur the first 5 minutes after the
compressor starts.
4. Allow at least 12 hours for the
crankcase heater to warm up at initial
startup. This will remove from the
crankcase any liquid refrigerant that has
accumulated during shipping and storage.
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