Friedrich VERT-I-PAK VHA-18K75RTP, Service & Parts Manual

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40 PB
COMPONENT TESTING
Reversing Valve Description And Operation
The Reversing Valve controls the direction of refrigerant flow to the indoor and outdoor coils. It consists of a
pressure-operated, main valve and a pilot valve actuated by a solenoid plunger. The solenoid is energized during
the heating cycle only. The reversing valves used in the RAC system is a 2-position, 4-way valve.
The single tube on one side of the main valve body is the high-pressure inlet to the valve from the compressor.
The center tube on the opposite side is connected to the low pressure (suction) side of the system. The other two
are connected to the indoor and outdoor coils. Small capillary tubes connect each end of the main valve cylinder
to the “A” and “B” ports of the pilot valve. A third capillary is a common return line from these ports to the suction
tube on the main valve body. Four-way reversing valves also have a capillary tube from the compressor discharge
tube to the pilot valve.
The piston assembly in the main valve can only be shifted by the pressure differential between the high and low
sides of the system. The pilot section of the valve opens and closes ports for the small capillary tubes to the main
valve to cause it to shift.
NOTE: System operating pressures must be near normal before valve can shift.
A
B
Figure 702 (Reversing Valve)