Nordic R-09, Installation And Service Manual, Page: 36 / 60

11-May-2021 Page 36 002512MAN-01
OPERATION TROUBLESHOOTING - COOLING MODE
Fault Possible Cause Verification Recommended Action
High Discharge
pressure
Unit is overcharged
(Only possible if unit has
been field serviced and
incorrectly charged)
High subcooling, low delta T across
water coil.
Remove 1/2lb of refrigerant at a
time and verify that the discharge
pressure reduces. Or remove
charge and weigh back in the
amount listed on nameplate.
High Suction
Pressure
(may appear to
not be pumping)
TXV adjusted too far open Verify superheat. It should be be-
tween 8-12°F (3-6°C). Superheat
will be low if TXV is open too far.
Adjust TXV to obtain 8-12°F
(3-6°C) superheat.
TXV stuck open Adjusting the TXV does not affect
the superheat or the suction pres-
sure. Low super heat and dis-
charge pressure.
Adjust the TXV all the way in and out a
few times to loosen it. Replace TXV if
this does not work.
Leaking reversing valve Reversing valve is the same tem-
perature on both ends of body,
common suction line is warm, com-
pressor is running hot.
Replace reversing valve.
Faulty compressor, not
pumping
Pressures change only slightly from
static values when compressor is
started.
Replace compressor.
Low Suction
Pressure
Low airflow See Fan Troubleshooting section.
Note: low airflow will cause the
air coil to ice up once the suction
drops below 90PSIG .
Correct the problem.
TXV stuck almost closed
or partially blocked by for-
eign object
Adjusting the TXV does not affect
the superheat or the suction pres-
sure. TXV may be frosting up.
Adjust the TXV all the way in and
out a few times to loosen it. Re-
place TXV if this does not work.
Low or no refrigerant
charge
Entering air temperature and air-
flow are good but suction is low.
Check static refrigeration pressure
of the unit for a very low value.
Weigh refrigerant out and compare
to charge listed on nameplate.
Locate the leak and repair it.
Spray 9, a sniffer, and dye are
common methods of locating a
leak.
Compressor
frosting up
See Low Suction
Pressure in this section
TXV frosting up TXV stuck almost closed
or partially blocked by for-
eign object.
Adjusting the TXV does not affect
the superheat or the suction pres-
sure.
Adjust the TXV all the way in and out a
few times to loosen it. Replace TXV if
this does not work.
Random Low
Pressure trip
(does not occur
while there)
Faulty compressor
contactor
Points pitted or burned. Contactor
sometimes sticks causing the com-
pressor to run without the fan, trip-
ping the low pressure control.
Replace contactor.
Intermittent fan See Fan Troubleshooting section. Correct the problem.