Friedrich SM21J30A4, Руководство по обслуживанию

Страница: 38 / 70

38
SOLENOID COIL
(Heat Pump Models Only) (See Figure 37)
The solenoid coil is an electromagnetic type coil mounted on
the reversing valve and is energized during the operation of
the compressor in the heating cycle.
Should the reversing valve fail to shift during the heating cycle,
test the solenoid coil.
TO TEST:
1. Disconnect power to unit.
2. Disconnect coil leads.
3. Attach probes of an ohmmeter to each coil lead and check
for continuity.
NOTE: Do not start unit with solenoid coil removed from valve,
or do not remove coil after unit is in operation. This
will cause the coil to burn out.
VALVE, DRAIN PAN (See Figure 38)
During the cooling mode of operation, condensate which
collects in the drain pan is picked up by the condenser fan
blade and sprayed onto the condenser coil. This assists in
cooling the refrigerant plus evaporating the water.
During the heating mode of operation, it is necessary that water
be removed to prevent it from freezing during cold outside
temperatures. This could cause the condenser fan blade to
freeze in the accumulated water and prevent it from turning.
To provide a means of draining this water, a bellows type drain
valve is installed over a drain opening in the base pan.
This valve is temperature sensitive and will open when the
outside temperature reaches 40°F. The valve will close
gradually as the temperature rises above 40°F to fully close
at 60°F.
REVERSING VALVE
BELLOWS ASSEMBLY
DRAIN PAN VALVE
Figure 37
Figure 38
TESTING REVERSING VALVE
Occasionally, the reversing valve may stick in the heating or
cooling position or in the mid-position.
When stuck in the mid-position, part of the discharge gas from
the compressor is directed back to the suction side, resulting
in excessively high suction pressure.
Check the operation of the valve by starting the system and
switching the operation from "Cooling" to "Heating" and then
back to "Cooling". Do not hammer on valve.
If valve fails to change its position, test the voltage to the valve
coil while the system is in the heating cycle. If voltage to coil is
satisfactory, replace reversing valve.
Should the valve fail to shift from cooling to heating, block the
air flow through the outdoor coil and allow the discharge
pressure to build in the system. Then switch the system from
heating to cooling.
If the valve is stuck in the heating position, block the air flow
through the indoor coil and allow discharge pressure to build
in the system. Then switch the system from heating to cooling.
Should the valve fail to shift in either position after increasing
the discharge pressure, replace the valve.
NOTE: When brazing a reversing valve into the system, it is
of extreme importance that the temperature of the valve does
not exceed 250° F at any time.
Wrap the reversing valve with a large rag saturated with
water. "Re-wet" the rag and thoroughly cool the valve after
each brazing operation of the four joints involved.
The wet rag around the reversing valve will eliminate
conduction of heat to the valve body when brazing the line
connection.