Nordic R-45, Installation And Service Manual, Page: 49 / 91

1-Nov-2021 Page 49 001200MAN-09
PLENUM HEATER TROUBLE SHOOTING
Fault Possible Cause Verification Recommended Action
No 24VAC signal
from 1 to ground
at the plenum
heater control
connector
Faulty Plenum Heater
Relay in heat pump
24VAC is present across pin 1 and
pin 3 of the relay, 24VAC is present
from heat pump terminal strip I to
plenum heater ground, but not from
heat pump terminal strip 1 to plenum
heater ground.
Replace relay.
Fan not operating See Fan/Blower Troubleshooting
section
Correct problem. Reset thermal
overload.
Faulty overload Reset thermal overload Replace if faulty.
Plenum heater
thermal overload
is tripped.
DOMESTIC HOT WATER (DESUPERHEATER) TROUBLE SHOOTING
Fault Possible Cause Verification Recommended Action
Insufficient hot
water (tank
problem)
Thermostat on hot water
tank set too low; should
be set at 120°F to 140°F
Visually inspect the setting. Adjust the setting.
Breaker tripped, or fuse
blown in electrical supply
to hot water tank
Check both line and load sides of
fuses. If switch is open determine
why (possible shorted element).
Correct problem, and replace
blown fuse or reset breaker.
Reset button tripped on
hot water tank
Check voltage at elements with
multimeter.
Push reset button.
DHW switch is turned off Inspect switch, located on heat
pump cabinet post.
Turn switch on.
Blockage or restriction in
the water line or hot water
heat exchanger
Check water flow and power to
pump. Check water lines for
obstructions.
Remove obstruction in water
lines. Acid treat the domestic hot
water coil.
Faulty DHW cutout (failed
open)
Check contact operation. Should
close at 120°F and open at 140°F.
Replace DHW cutout if faulty.
Heat pump not running
enough hours to make
sufficient hot water
Note the amount of time the heat
pump runs in any given hour.
Temporarily turn up the tank
thermostats until colder weather
creates longer run cycles.
Water is too hot. Faulty DHW cutout (failed
closed)
Check contact operation. Should
close at 120°F and open at 140°F.
Replace DHW cutout if faulty.
Thermostat on hot water
tank set too high; should
be set at 120°F to 140°F
Visually inspect the setting. Adjust the setting.
Insufficient hot
water
(heat pump
problem)
Circulator pump seized or
motor failed
Use an amprobe to measure current
draw.
Replace if faulty.