Figure 6-53.Connections for low-side charging.
the line with gas and clears the air from the line.
After clearing, tighten the connection.
Connect a line from the LOW (LO) valve
(suction) on the gauge manifold set to the
suction service valve of the compressor.
Start the compressor.
Open the valve on the cylinder and the LOW
(LO) valve (suction) on the gauge manifold set.
Open the suction service valve on the
compressor to permit the gas to enter the
compressor where it will be compressed and fed
to the high side. Add the refrigerant slowly and
check the liquid level indicator regularly until
the system is fully charged. It is easy to check
the receiver refrigerant level in some makes of
condensing units because the receiver has
minimum and maximum liquid level indicator
valves which show the height of the liquid level
when opened. If a liquid line sight glass is used,
the proper charge may be determined when
there is no bubbling of refrigerant as it passes by
the glass. The sight glass will appear empty.
Again, be certain the refrigerant cylinder is in the
vertical position at all times; otherwise, the liquid
refrigerant will enter the compressor and, liquid not
being compressible, damage the piston or other parts of
system is when there is enough pressure to increase the
The best ti me to test joints and connections in a
rate at which the refrigerant seeps from the leaking
joint. There is usually enough pressure in the
high-pressure side of the system; that is, in the
condenser, receiver, and liquid line, including
dehydrators, strainers, line valves, and solenoid
valves. This is not necessarily true of the low-pressure
side of the system, especially if it is a low-pressure
installation, such as for frozen foods and ice cream,
where pressures may run only slightly above zero on
the gauge. When there is little pressure, increase the
pressure in the low-pressure side of the system by
bypassing the discharging pressure from the condenser
to the low-pressure side through the service gauge
manifold Small leaks cannot be found unless the
pressure inside the system is at least 40 to 50 psi,
regardless of the method used to test for leaks.
Halide Leak Detector
The use of a halide leak detector (fig. 6-54) is the
most positive method of detecting leaks in a refrigerant
system using halogen refrigerants (R-12, R-22, R-11,
R-502, etc.). Such a detector consists essentially of a
torch burner, a copper reactor plate, and a rubber
Detectors use acetylene gas, alcohol, or propane as
a fuel. A pump supplies the pressure for a detector that
uses alcohol. If a pump-pressure type of alcohol-
burning detector is used, be sure that the air pumped
into the fuel tank is pure.
Figure 6-54.Halide leak detector.