Series 7 Installation Manual
ClimateWorx uses a single valve head pressure control, with a heated receiver for factory ordered
condensers. The OROA is located in the liquid drain line between the condenser and the receiver, and has
a bypass line from the hot gas line.
During periods of low ambient temperature, the condensing pressure falls until it approaches the setting of
the OROA valve. The valve (non-adjustable) then throttles, restricting the flow of liquid from the
condenser. This causes refrigerant to back up in the condenser thus reducing the active condenser surface.
This raises the condensing pressure. Since it is really the receiver pressure that needs to be maintained,
the bypass line is required to heat up the cold liquid being passed by the OROA. Thus the liquid reaches
the receiver warm and with sufficient pressure to assure proper expansion valve operation. As long as
sufficient refrigerant charge is in the system, the valve modulates the flow automatically to maintain
proper receiver pressure regardless of outside ambient.
Charging
When head pressure control is utilized, there must be enough refrigerant to flood the condenser at the
lowest expected ambient and still have enough charge in the system for proper operation. After
completing the evacuation procedures follow these guidelines for charging:
1. Close the main power and allow the compressor crankcase heater to operate for at least one hour.
2. Connect the gauge manifold to both suction and liquid service valves, with the common connection
to the refrigerant drum. Purge the lines and open the refrigerant drum vapor valve.
3. Start the compressor using the test mode to energize the main fan and compressor.
4. Open the suction connection on the gauge manifold. Modulate the rate of charging with the gauge
manifold valve. Watch the discharge pressure closely during the charging operation to ensure that the
system is not overcharged. It is a good practice to weigh the amount of gas added.
5. Charge the system until the sight glass is clear of bubbles. The system is now correctly charged for
operating under head pressure control at the ambient temperature charging is being carried out.
6. If the system is designed to operate at ambient below the ambient that exists during the charging, additional
charge will have to be added now.
7. Read from the following table the percentage of condenser to be flooded at charging and that at expected
minimum ambient temperature, then calculate the difference:
Ambient Temperature in °F Percentage of Condenser to be Flooded
70 0
65 0
60 10
55 24
50 33
45 41
40 46
35 52
S7-IM2014.DOC 2014
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