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NOTE: System operating pressures must be near
normal before valve can shift.
REVERSING VALVE DESCRIPTION/OPERATION
The Reversing Valve controls the direction of refrigerant fl ow
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 PTAC 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.
ELECTRIC SHOCK HAZARD
WARNING
Disconnect power to the unit before servicing.
Failure to follow this warning could result in
serious injury or death.
TESTING THE COIL
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.
1. Turn off high voltage electrical power to unit.
2. Unplug line voltage lead from reversing valve coil.
3. Check for electrical continuity through the coil. If you
do not have continuity replace the coil.
4. Check from each lead of coil to the copper liquid line
as it leaves the unit or the ground lug. There should
be no continuity between either of the coil leads
and ground; if there is, coil is grounded and must be
replaced.
5. If coil tests okay, reconnect the electrical leads.
6. Make sure coil has been assembled correctly.
ELECTRIC SHOCK HAZARD
WARNING
Unplug and/or disconnect all electrical power
to the unit before performing inspections,
maintenances or service.
Failure to do so could result in electric shock,
serious injury or death.
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.
CHECKING THE REVERSING VALVE
NOTE: You must have normal operating pressures before
the reversing valve can shift.
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.
Occasionally, the reversing valve may stick in the heating
or cooling position or in the mid-position.
Sealed Refrigeration System contains refrigerant
and oil under high pressure.
Proper safety procedures must be followed,
and proper protective clothing must be worn
when working with refrigerants.
Failure to follow these procedures could
result in serious injury or death.
WARNING
HIGH PRESSURE HAZARD
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