Trane TR-SCS Series Installation, Operation And Maintenance Manual page 9

When ambient temperature drops, the discharge pressure
drops also. When the discharge pressure drops, the head
pressure control valve diverts discharge gas away from
the condenser to the receiver. Liquid flow from the
condenser is restricted, causing liquid to back up in the
condenser.
Flooding the condenser reduces the area available for
condensing. The desired result is to increase the pressure
into the condenser, maintaining a minimum discharge
pressure during low ambient operation thus ensuring
proper condensing temperature. The head pressure
control valve requires no adjustment.
Figure 3. Flooded head pressure control diagram
SS-SVX006C-EN
PRESSURE
RELIEF VALVE
REFRIGERANT
RECLAIM VALVE
RECEIVER
CHECK
VALVE
(SEE NOTE)
HEAD PRESSURE
CONTROL VALVE
REMOTE AIR COOLED
CONDENSER
This method of controlling head pressure allows the
condenser fan to run continuously. While the fan is
running, the flooded head pressure control valve
modulates the amount of discharge gas entering the
receiver. As the pressure increases, the valve diverts more
discharge gas to the condenser, allowing more liquid to
flow from the condenser to the receiver.
When using this method of head pressure regulation there
must be enough refrigerant in the system to ensure an
adequate charge at the lowest expected ambient
temperature in which the system will be operating. A
receiver is used to store the extra refrigerant when the
condenser is not utilizing it.
LIQUID LINE
DISCHARGE LINE
NOTE: SEPARATE CHECK VALVE IS PROVIDED
ONLY ON SMALL A/C UNITS UP TO 3 TONS
Introduction
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