Carrier 50HQ - Manual (Page 13)

TROUBLESHOOTING CHART
PROBLEM CAUSE CORRECTION
ENTIRE UNIT DOES
NOT RUN
Blown fuse
Broken or loose wires
Voltage supply low
Transformer
Tfiermostat
Replace fuse or reset circuit breaker
Replace or tighten the wires
If volfage 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 thermo­
stat 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 terminals and unit should run.
BLOWER OPERATES
BUT COMPRESSOR
DOES NOT
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)
If voltage is below minimum voltage specified on the dataplate, contact local power
company
Ciieck 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 compressor runs, unit was off on high pres­
sure (See Problems for possible causes )
If the unit still fails to run, check for faulty pressure switch by jumpering the high pres­
sure 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 com­
pressor still does not start, replace the compressor
In all cases, an external or internal temperature sensitive compressor overload is used
If tfie compressor dome is too hot to touch, the overload will not reset until the com­
pressor 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, other­
wise replace the compressor
Internal winding grounded to the compressor shell Replace the compressor.
Check continuity of the compressor windings with an ohmmeter 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).
UNIT OFF ON LOW
WATER TEMPERA­
TURE CONTROL
Water temperature too low
on heating
Low water temperature
switch
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
UNIT CYCLING ON
HIGH-PRESSURE
CUTOUT CONTROL Discharge pressure too high
Refrigerant charge
High pressure switch
On COOLING cycle:
Lack of or inadequate water flow.
Entering water too warm.
Scaled or plugged heat exchanger.
On^Fli^TTNlJcycle: “ " ^ ................
Lack of or inadequate airflow
Entering air too hot.
-§J°.yy§Lj.P9.P§r§tiy£' SlPaaSfi filter or cojh restrictions in ductwork.
The unit is overcharged with refrigerant Bleed off some charge or evacuate and re­
charge with specified amount of R-22
Check for defective or improperly calibrated high pressure switch.
UNIT SHORT
CYCLES
Wiring and controls
Compressor overload
Loose connections in the wiring or the control contactors defective
Defective comprAsor overload, check and replace if necessary If the compressor runs
too hot, it may be due to the deficient refrigerant charge
INSUFFICIENT
COOLING OR
HEATING
Unit undersized
Loss of conditioned
air by leaks
Thermostat
Airflow
Refrigerant charge
Compressor
Reversing valve
Operating pressure
Refrigerant system
Recalculate heat gains or losses for space to be conditioned If excessive, rectify by add­
ing insulation, shading, etc.
Check for leaks in ductwork or introduction of ambient air thru doors and windows.
Improperly located thermostat (e g near kitchen sensing inaccurately the comfort level
In living areas).
Lack of adequate airflow or improper distribution of air
Low on refrigerant charge causing inefficient operation
Check for defective compressor If discharge pressure is too low and suction pressure is
too high, compressor is not pumping properly. Replace corhpressor
Defective reversing valve creating bypass of refrigerant from discharge to suction side of
compressor
Incorrect operating pressure. (See chart )
Check strainer and capillary tubes for possible restrictions to flow of refrigerant.
The
refrigerant system may be contaminated with moisture, noncondensables, and
particles
Dehydrate, evacuate and recharge the system
13