Adjustments
HALOGEN LEAK DETECTOR TEST.--The
use of a halogen leak detector is the most positive
The adjustments of the many valves and solenoids
method of detecting leaks in a refrigerant system (fig.
have one thing in common--they are very sensitive and
11-27). It is a portable, battery operated electronic leak
only one turn, or two at the most, is all that is required at
detector. It is capable of finding leaks as small as
a time. Then, the system has to run for a while until all
ounce per year as well as large leaks in areas where
readings stabilize. With this in mind, you can see that
background contamination may be present.
consulting the manual (with all of its tables of normal
The instrument features a variable frequency alarm
settings and relationship charts) is a necessity when
signal that gives an indication of the concentration of
performing maintenance on an air-conditioning
halogen gases (size of leak). It permits the operator to
system.
"home in" on the leak source without continually
Superheat is adjusted by the thermostatic expan-
readjusting the instrument for the changing ambient or
sion valve, which meters the amount of liquid entering
background contamination.
the evaporator coil. When adjusting the valve, turning
The sensing tip (Qutip) at the end of the probe is not
the valve stem counterclockwise two full turns
adversely affected by large amounts of refrigerant, as
increases superheat about 1 degree. Turning the stem
are vacuum-type halogen gas detectors. Recovery time
clockwise decreases superheat about 1 degree for each
after the probe is removed from a contaminated area is
two turns.
virtually instantaneous.
The temperature control, which senses outlet air
This instrument requires no warm-up period, and it
temperature, is a two-stage control. Each stage controls
is ready to use following a simple balancing procedure.
a solenoid valve that, in turn, feeds liquid refrigerant to
It is equipped with a dual length flexible probe, which
each section of the aftercooler coil. As delivered air
can be bent to permit the sensing tip (Qutip) at the end
temperature falls below the set point, the first stage of
of the probe to reach normally inaccessible areas.
the temperature controls actuates and closes one of the
two aftercooler liquid line solenoid valves. Set the
Always be sure your instrument is off when
temperature to meet the needs of your climate area and
changing tips. The battery voltage is amplified in the
to your cooling needs.
sensing tip (Qutip). Failure to turn the instrument off
when changing tips can result in a mild shock and
Other adjustments available to you are the
possible damage to the instrument.
compressor cylinder unloaders, the hot gas bypass
regulator, and the condenser fan speed regulator.
When leak detection is necessary, make sure the
You should follow the settings in the technical
following steps are taken before use:
manual to achieve maximum efficiency from your
air-conditioning system.
Testing for Refrigerant Leaks
The best time to test joints and connections in a
system is when there is sufficient pressure to increase
the rate at which the refrigerant is leaking from the
component. There is usually sufficient pressure in the
high-pressure side of the system; that is, in the
Thermal
condenser, receiver, and liquid line, including
xxxxx
Model No. 1947
dehydrators, strainers, line valves, and solenoid valves.
However, this is not necessarily true of the low-pressure
side of the system. Where there is very little pressure,
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you can increase the pressure in the low-pressure side
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
ASf11027
pressure inside the system is at least 40 to 50 psi,
regardless of the method used to test.
Figure 11-27.--Halogen leak detector.
11-28
