cover the refrigerant in long runs of suction and discharge lines, etc. It is essential that the maximum operating
charge be determined, e.g., winter charge in air cooled condenser having flooded head pressure control, this being
much greater than the normal summer charge.
Safety Relief Devices
A refrigerant safety relief device is designed to prevent pressure in a receiver from rising above a safe limit when
operating controls fail or when the receiver is exposed to excessive heat. When a receiver, containing liquid
refrigerant, is shut off from other parts of the system a rise in temperature will cause a rise in pressure. If the
receiver is filled with liquid a small rise in temperature will cause a rapid and excessive rise in pressure due to the
expansion of the liquid. If the receiver contains both liquid and vapor, which is normal for refrigerant receivers, the
pressure will rise according to the temperature-pressure saturation characteristic of the refrigerant. If pressure
builds up high enough to cause the receiver to rupture, large quantities of liquid refrigerant are released. This causes
a sudden reduction of pressure so that the liquid released is vaporized almost instantly with explosive results. With
a suitable relief device installed on the receiver, the refrigerant is released at a controlled rate and a safe pressure
is maintained in the receiver.
NOTE: After a “Direct Type” relief device has discharged once, it should be replaced. Be safe and replace the device
after such an occurrence.
Refrigerant Receiver Installation
1. Install the liquid refrigerant receiver after the condenser and before the liquid line filter drier.
2. An NPT fitting is provided on select models at the top of the receiver for installation of a pressure relief
device. The installer must ensure the receiver is protected from over-pressure.
3. A 1/8 NPT fusible plug is included on select models to protect the receiver from over-pressure due to
excessive heat. Replace the fusible plug immediately if the stamped temperature rating is exceeded.
Head Pressure Control
The receiver has a head pressure control valve to maintain flooded condenser control. A receiver with pressure
control is provided for each circuit.
Receiver Levels
Identify and log the refrigerant level of the receiver of each refrigeration system using the Data Aire Monthly
Refrigerant Receiver Level Table. Be sure the refrigeration systems are not in winter flooding mode, or any other
condition that could affect receiver level. Compare the current refrigerant level with levels logged during previous
checks. A drop in the receiver level from a previous reading may indicate a leak in the system. A significant drop in
refrigerant level must be the result of a significant leak. Do not stop at the first leak found, especially if it is a seeping
connection or valve stem leak. Continue searching until a significant leak is found.
If a receiver is being used in a system for low ambient head pressure control, additional refrigerant will be required.
See below for the approximate receiver capacities. Note that receivers should not be filled more than 90% of full
internal volume.
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