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COMMON CAUSES FOR UNSATISFACTORY
OPERATION OF HEAT PUMPS IN HEATING MODE
Dirty Filters
Dirty filters or inadequate airflow through the indoor coil. Failure
to keep clean filters and adequate airflow (375-425 CFM/ton) will
cause excessive discharge pressures that may cause the high-pres-
sure switch to function.
Low Return Air Temperatures
Return ductwork temperatures that are less than 60°F will cause
low discharge pressure, low suction pressure and excessive de-
frost cycling.
Undercharging
An undercharged system will cause low discharge pressure, low
suction pressure and an accumulation of frost on the lower sec-
tion of the outdoor coil.
Sol e n oi d d oe s n o t e n e rgi ze w h e n vol ta ge i s p re s e n t.
No vol ta ge to th e s o l e n oi d .
Th e va l ve wi l l n ot s h i ft.
a . Un d e rch a rge d
b . Va l ve b od y d a m a ge
c. Va l ve s ti cki n g
Poor Termination of Defrost
The defrost sensor must make good contact with the outside coil
return bend or a non-termination of defrost may occur.
Reversing Valve
A reversing valve may not function correctly for the following rea-
sons:
Replace the reversing valve.
Check the wiring.
Check for leaks
Replace the reversing valve
Replace the reversing valve
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