REFRIGERATION NOTES
(
Review vapor/compression system in introduction)
For many years, the most common refrigerant used in residential split air conditioning systems was R‐22, but with the
current changes in the industry, read the nameplate to determine the type of refrigerant used.
Filter driers will remove moisture from the refrigerant in a system, but there is a limit to their capacity. Some sys‐
tems are equipped with a moisture indicating sight glass. When the sight glass changes color, the system contains
excessive moisture and will need to be evacuated. The filter‐drier should be replaced anytime a system is opened for
servicing. If a strong odor is detected during the recovery process, a compressor burn‐out may have occurred. When
recovering refrigerant from a system that experienced a compressor burn‐out, watch for signs of contamination in the
oil.
A crankcase heater is often used to prevent refrigerant from migrating to the oil during periods of low ambient tem‐
perature. Refrigerant in the oil will cause oil foaming in the compressor at start‐up.
When evacuating a vapor compression system, the vacuum pump should be capable of pulling 500 microns (29.90” hg.)
of vacuum. The more accurate and preferred method of measuring a deep vacuum is in microns.
Warning: A hermetic compressor's motor winding could be damaged if energized when under a deep vacuum.
The use of a large vacuum pump could cause trapped water to freeze. During evacuation of systems with large
amounts of water, it may be necessary to increase pressure by introducing nitrogen to counteract freezing.
The source of most non‐condensables is air. Non‐condensables will cause higher discharge pressures.
Where there is a risk of freezing, charging of an R‐12 refrigeration system should begin with vapor from a vacuum level
to a pressure of approximately 33 psig. followed by a liquid charge through the liquid‐line service valve. This is also the
proper method to charge a system that contains a large quantity of refrigerant.
SAFETY
(Additional Safety and shipping information is covered in the core section of this manual.)
ASHRAE standard 15 requires a refrigerant sensor that will sound an alarm and automatically start a ventilation system
in occupied equipment rooms where refrigerant from a leak will concentrate.
Refrigerants CFC‐12, CFC‐11, and HFC‐134a are categorized as A‐1.
All refrigeration systems must be protected by a pressure relief valve (s) (must not be installed in series).
NEVER energize a reciprocating compressor if the discharge service valve is closed.
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