Nordic ATWC Series, Installation And Service Manual, Page: 65 / 106

PRELIMINARY: 24-Sep-2021 Page 65 002536MAN-00
OPERATION TROUBLESHOOTING - DEFROST & COOLING MODES
Fault Possible Cause Verification Recommended Action
High suction pres-
sure
(may appear to
not be pumping):
Stage 1 - R410a or
Stage 2 - R134a
Indoor unit’s EEV1 or
EEV2 stuck open
Manually adjusting the indoor EEV
does not affect the superheat or the
suction pressure. Low superheat
and low discharge pressure.
Go to EEV troubleshooting sec-
tion.
Leaking reversing valve
(Stage 2 R134a only)
Reversing valve is the same tem-
perature on both ends of body,
common suction line is warm, com-
pressor is running hot, low com-
pressor discharge pressure.
Replace reversing valve.
Faulty compressor, not
pumping
Pressures change only slightly from
static values when compressor is
started.
Replace compressor.
Low indoor loop liquid flow Check for high delta T with the PC
APP. The EEV will be at a lower
position than normal as well.
Correct the problem.
Indoor unit’s EEV1 or
EEV2 stuck almost closed
or partially blocked by for-
eign object
Manually adjusting the indoor EEV
does not affect the superheat or the
suction pressure. High superheat
and high discharge pressure.
Go to EEV troubleshooting sec-
tion.
TS1 or TS2 temperature
sensor not reading proper-
ly
If the sensor is reading low it will
cause the superheat to appear
high, which causes the EEV to con-
tinually close.
Verify EEV position is low com-
pared to normal. Check tempera-
ture sensor, replace if necessary.
Filter-dryer plugged Feel each end of the filter-dryer;
they should be the same tempera-
ture. If there is a temperature dif-
ference then it is plugged. Also
causes high discharge pressure.
Replace filter-dryer.
Low refrigerant charge Water flow rate is good but suction
is still low. Check static refrigera-
tion pressure of unit for a low value.
Locate the leak and repair it.
Spray Nine, a sniffer, and dye are
common methods of locating a
leak.
Compressor frost-
ing up
See Low Suction
Pressure in this section
Indoor unit’s EEV
frosting up
Indoor unit’s EEV1 or
EEV2 stuck almost closed
or partially blocked by for-
eign object
Manually adjusting the indoor EEV
does not affect the superheat or the
suction pressure. High superheat
and high discharge pressure.
Go to EEV troubleshooting sec-
tion.
Random manual
high pressure trip
(may not occur
while on site)
Faulty compressor contac-
tor
Points pitted or burned. Contactor
sometimes sticks causing the com-
pressor to run when it should be
off.
Replace contactor.
Low suction
pressure:
Stage 1 - R410a or
Stage 2 - R134a