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Refrigeration System Head Pressure Control

The condenser has to be sized for the heat of rejection during the summer conditions. During colder outdoor temperatures the condenser is oversized and low head pressure results. This will cause erratic operation of the expansion valve. Some method of head pressure control is required. The selection of which method is dependent on how cold the ambient conditions are and what reliability is required. The two commonly used methods are condenser fan speed control and flooded condenser control.

Refrigeration System Head Pressure Control
Refrigeration System Head Pressure Control

Fan Speed Control

The condenser fan speed control can provide reliable operation when the outdoor temperature is as low as -29 deg C. The components required are, a condenser fan motor designed for variable speeds to be used in conjunction with a solid state fan-speed control and a refrigerant transducer. The transducer senses the head pressure of the compressor and the fan speed control varies the speed of the fan to maintain a constant condensing temperature. On a multi fan condenser the additional fan motors are controlled by ambient thermostats.

Flooded Condenser

With flooded condenser control we can provide reliable operation when the outdoor temperature is as low as -34 deg C.

The components required are, heated and insulated receivers and a head pressure control valve.

The heated and insulated receivers maintain sufficient pressure for starting at -34 deg C.

The head pressure control valve restricts the flow of refrigerant from the condenser in the cold weather. T

his causes the refrigerant to back up in the condenser which reduces the effective condenser surface. As the head pressure control valve is restricting flow from the condenser it is also bypassing hot-gas into the receiver insuring proper head pressure is maintained.

Refrigeration System Head Pressure Control

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