57
SERVICING
Undercharge
An undercharged heat pump on the heating cycle will
cause low discharge pressure resulting in low suction
pressure and frost accumulation on the outdoor coil.
Poor “Terminating” Sensor contact
The unit’s defrost terminating sensor must make good
thermal contact with the outdoor coil tubing. Poor contact
may not terminate the unit’s defrost cycle quickly enough
to prevent the unit from cutting out on high discharge
pressure.
Malfunctioning Reversing Valve - This may be due to:
1.
Solenoid not energized
- In order to determine if the
solenoid is energized, touch the nut that holds the
solenoid cover in place with a screwdriver. If the nut
magnetically holds the screwdriver, the solenoid is
energized and the unit is in the cooling cycle.
2.
No voltage at unit’s solenoid
- Check unit voltage. If
no voltage, check wiring circuit.
3.
Valve will not shift
:
A. Undercharged
- check for leaks;
B. Valve Body Damaged
- Replace valve;
C. Unit Properly Charged
- If it is on the heating
cycle, raise the discharge pressure by restricting
airflow through the indoor coil. If the valve
does not shift, tap it
lightly
on both ends with
a screwdriver handle.
DO NOT TAP THE VALVE
BODY
. If the unit is on the cooling cycle, raise
the discharge pressure by restricting airflow
through the outdoor coil. If the valve does not
shift after the above attempts, cut the unit off
and wait until the discharge and suction pressure
equalize, and repeat above steps. If the valve
does not shift, replace it.
S-50 Checking Heater Limit Control(s)
(OPTIONAL ELECTRIC HEATERS)
Each individual heater element is protected with an
automatic rest limit control connected in series with each
element to prevent overheating of components in case
of low airflow. This limit control will open its circuit at
approximately 150°F. to 160°F and close at approximately
110°F.
WARNING
Disconnect ALL power before servicing.
1. Remove the wiring from the control terminals.
2. Using an ohmmeter test for continuity across the
normally closed contacts. No reading indicates the
control is open - replace if necessary. Make sure the
limits are cool before testing.
IF FOUND OPEN - REPLACE - DO NOT WIRE AROUND
.
S-52 Checking Heater Elements
Optional electric heaters may be added, in the quantities
shown in the spec sheet for each model unit, to provide
electric resistance heating. Under no condition shall more
heaters than the quantity shown be installed.
HIGH VOLTAGE!
Disconnect ALL power before servicing
or installing this unit. Multiple power
sources may be present. Failure to do so
may cause property damage, personal injury
or death.
1. Disassemble and remove the heating element(s).
2. Visually inspect the heater assembly for any breaks in
the wire or broken insulators.
3. Using an ohmmeter, test the element for continuity -
no reading indicates the element is open. Replace as
necessary.
S-100 Refrigeration Repair Practice
DANGER
Always remove the refrigerant charge in a proper
manner before applying heat to the system.
When repairing the refrigeration system:
WARNING
Disconnect ALL power before servicing.
1. Never open a system that is under vacuum. Air and
moisture will be drawn in.
2. Plug or cap all openings.
3. Remove all burrs and clean the brazing surfaces of the
tubing with sand cloth or paper. Brazing materials do
not flow well on oxidized or oily surfaces.
4. Clean all tubing by using a dry clean cloth.
5. Insure that the nitrogen is being vented to prevent
back pressure which could result in leaks.
Summary of Contents for DRG0361DL00001S
Page 20: ...20 SYSTEM OPERATION...
