Friedrich SM21J30A4, Руководство по обслуживанию

Страница: 37 / 70

37
DUAL RATED RUN
CAPACITOR HOOK-UP
3. For dual rated, apply an ohmmeter lead to common (C)
terminal and the other probe to the compressor (HERM)
terminal. A satisfactory capacitor will cause a deflection
on the pointer, then gradually move back to infinity.
4. Reverse the leads of the probe and momentarily touch
the capacitor terminals. The deflection of the pointer
should be two times that of the first check if the capacitor
is good.
5. Repeat steps 3 and 4 to check fan motor capacitor.
NOTE: A shorted capacitor will indicate a low resistance
and the pointer will move to the "0" end of the
scale and remain there as long as the probes are
connected.
An open capacitor will show no movement of the
pointer when placed across the terminals of the
capacitor.
CHECK VALVE
(See Figure 36)
A unique two-way check valve is used on the reverse cycle
heat pumps. It is pressure operated and used to direct the
flow of refrigerant through a single filter drier and to the proper
capillary tube during either the heating or cooling cycle
NOTE: The slide (check) inside the valve is made of
teflon. Should it become necessary to replace the
check valve, place a wet cloth around the valve
to prevent overheating during the brazing
operation.
CHECK VALVE OPERATION
In the cooling mode of operation, high pressure liquid enters
the check valve forcing the slide to close the opposite port
(liquid line) to the indoor coil. Refer to refrigerant flow chart.
This directs the refrigerant through the filter drier and cooling
capillary tube to the indoor coil.
In the heating mode of operation, high pressure refrigerant
enters the check valve from the opposite direction, closing
the port (liquid line) to the outdoor coil. The flow path of the
refrigerant is then through the filter drier and heating capillary
to the outdoor coil.
Failure of the slide in the check valve to seat properly in either
mode of operation will cause flooding of the cooling coil. This
is due to the refrigerant bypassing the heating or cooling
capillary tube and entering the liquid line.
HEAT PUMPS: REVERSING VALVE
(See Figure 37)
A reversing valve is used to change the refrigerant flow within
the system to permit heating or cooling.
The reversing valve consists of a main valve body which
houses the slide and piston, plus a pilot valve which is activated
by a solenoid.
There are three tubes connected to one side of the main valve
body and one tube on the opposite side. The single tube is
connected to the compressor discharge line. The center tube
on the opposite side is the common suction line to the
compressor. The outside tubes are connected to the indoor
and outdoor coils.
The pivot valve is responsible for directing the refrigerant flow
to the indoor or outdoor coil. There are three small tubes
connected to the pilot valve body. The center pilot tube is the
common pilot tube and is connected to the center suction line.
The outside tubes are connected to each end of the main
valve body. The pilot valve consists of a needle valve and
spring.
When the solenoid is de-energized, the spring tension closes
one pilot port while the other remains open. When the solenoid
is energized, the opposite end is closed. The piston in the
main valve is pressure operated and will always travel in the
direction of the open pilot tube port which provides a path to
the center tube. Pressure which will increase in the opposite
side of the valve will escape through a bleed port located in
each piston. When de-energized, the valve will be in the cooling
position.
ONE-WAY CHECK VALVE
Heat Pump Models)
Figure 35
Figure36