Carrier 50HQ - Manual (Page 13)

^ TROUBLESHOOTING CHART
PROBLEM
ENTIRE UNIT DOES
NOT RUN
CAUSE
Blown fuse
Broken or loose wires
Voltage supply low
Transformer
Thermostat
BLOWER OPERATES
BUT COMPRESSOR
DOES NOT
UNIT OFF ON LOW
WATER TEMPERA­
TURE CONTROL
UNIT SHORT
CYCLES
Voltage supply low
Thermostat
Wiring
High-pressure controls
Defective capacitor
Seized compressor
Compressor overload open
Compressor motor grounded
Compressor windings open
Low water temperature
cutout open (LWTC)
Water temperature too low
on heating
Low water temperature
switch
Wiring and controls
Compressor overload
CORRECTION
Replace fuse or reset circuit breaker.
Repiace or tighten the wires.
If voltage is below minimum voltage specified on dataplate, contact
local power company
Check 24-volt transformer for burnout or voltage less than 18 volts
Set thermostat on COOL and lowest temperature setting, unit
should run Set thermostat on HEAT and highest temperature
setting, unit should run. Set fan to ON, fan should run If unit does
not run in all 3 cases, the thermostat could be wired incorrectly,
or faulty To ensure faulty or miswired thermostat, disconnect
thermostat wires at unit and jumper between R, Y, G and W ter­
minals and unit should run
If voltage is below minimum voltage specified on the dataplate,
contact local power company
Check setting, calibration and wiring.
Check for loose or broken wires at compressor, capacitor or
contactor. ___ _____ ______ ___________ _________ _
The unit could be off on the high-pressure cutout control. Reset the
thermostat to OFF After a few minutes, turn to COOL If the com­
pressor runs, unit was off on high pressure (See Problems for
possible causes )
If the unit still fails to run, check for faulty pressure switch by
jumpering the high-pressure control
Check capacitor or Start Thermistor (PTC). If defective, remove,
replace and revise correctly.
Try a start capacitor in parallel with the run capacitor momentarily.
If the compressor starts but the problem reoccurs on starting,
install an auxiliary start kit The hard start kit is comprised of a
recommended start relay and correctly sized capacitor If the
compressor still does not start, replace the compressor
In all cases, an external or internal temperature sensitive com­
pressor overload is used If the compressor dome is too hot to
touch, the overload will not reset until the compressor cools down.
If the compressor is cool and the overload does not reset, there
may be a defective or open overload If the overload is external,
replace the overload, otherwise, replace the compressor
Internal winding grounded to the compressor shell. Replace the
compressor
Check continuity of the compressor windings with anohmmeter If
the windings are open, replace the compressor.
The unit could be off on the LWTC Reset the thermostat to OFF.
After a few minutes, turn to HEAT If the compressor runs, unit was
off on LWTC (see Problems for possible causes).
Lack«,of or inadequate water flow
Entering water too cold.
Scaled or plugged heat exchanger ____ _
Check for defective or improperly calibrated low water temperature
switch
Loose connections in the wiring or the control contactors defective
Defective compressor overload, check and replace if necessary If
the compressor runs too hot, it may be due to the deficient refrig­
erant charge
13