Nordic R-45, Installation And Service Manual, Page: 41 / 91

1-Nov-2021 Page 41 001200MAN-09
POWER SUPPLY TROUBLESHOOTING
Fault Possible Cause Verification Recommended Action
No power to the
heat pump
Disconnect switch open
(if installed)
Verify disconnect switch is in the
ON position.
Determine why the disconnect
switch was opened, if all is OK
close the switch.
Fuse blown /
breaker tripped
At heat pump disconnect box,
voltmeter shows 230VAC on the
line side but not on the load side.
Reset breaker or replace fuse with
proper size and type. (Time-delay
type “D”)
No display on
thermostat.
Transformer breaker
tripped
Breaker on transformer is sticking
out.
Push breaker back in. If it trips
again locate cause of short circuit.
Faulty wiring between
heat pump and thermostat
24VAC is not present across C and
R(R
H
) of the thermostat.
Correct the wiring.
Faulty Thermostat 24VAC is present across C and R
(R
H
) of the thermostat but thermo-
stat has no display.
Replace thermostat.
Faulty transformer Transformer breaker is not tripped,
230VAC is present across L1 and
L3 of the compressor contactor but
24VAC is not present across R
H
and C of the terminal strip.
Replace transformer.
The following steps are for troubleshooting the geothermal heat pump. If the problem is with the domestic hot water or the
plenum heater, proceed to those sections at the end of the troubleshooting guide. Repair procedures and reference refriger-
ation circuit diagrams can be found at the end of the troubleshooting guide.
STEP 1: Verify that the display is present on the thermostat. If it is not, proceed to POWER SUPPLY TROUBLESHOOTING, other-
wise proceed to STEP 2.
STEP 2: Remove the door and electrical box cover and check to see if there is a fault code on the control board. If there is, record
the fault code. Turn the power off, wait 10 seconds and turn the power back on. Set the thermostat to call for heating or
cooling depending on the season.
STEP 3: If a 24VAC signal does not appear across Y1 and C of the terminal strip within 6 minutes, proceed to the THERMOSTAT
TROUBLESHOOTING section, otherwise proceed to STEP 4.
STEP 4: If a fault code appears once a signal is present at Y1 and the compressor does not attempt to start, proceed to the FAULT
CODE TROUBLESHOOTING section, otherwise proceed to STEP 5.
STEP 5: If no fault codes appear and the compressor does not attempt to start, attempts to start but cannot, starts hard, or starts
but does not sound normal, proceed to the COMPRESSOR TROUBLESHOOTING section, otherwise proceed to STEP 6.
STEP 6: If the compressor starts and sounds normal, this means the compressor is OK and the problem lies elsewhere. Proceed
to the OPERATION TROUBLESHOOTING section.
NOTE: To speed up the troubleshooting process, the TEST jumper on the safety board can be placed to the YES position to
change the anti-short cycle timer to 5 seconds. Be sure to set it back to NO when servicing is complete . Be aware that if
left in the TEST position, functionality may automatically revert back to standard operation after a short period of time; re-
move jumper, install in standard position, run unit, and replace jumper in TEST position to re-activate.
Troubleshooting Guide
THERMOSTAT TROUBLESHOOTING
Fault Possible Cause Verification Recommended Action
No Y1 signal to
heat pump
(after 6 minutes)
Incorrect thermostat setup Thermostat does not indicate a call
for heat. No 24VAC signal present
across Y1 & C of the thermostat
Correct the setup.
Faulty thermostat to heat
pump wiring
24VAC signal present across Y1 & C
of the thermostat but not present
across Y1 & C of the terminal strip.
Correct or replace wiring
Faulty thermostat No 24VAC between Y1 & C of the
thermostat when a call is indicated.
Replace thermostat.