Chapter 3 HVAC Tools, Equipment, and Service Information 43
changes in an object cause the infrared waves given off
by the object to change. A sensor in the gauge reads the
change in infrared waves as a temperature change. Internal
circuitry converts sensor readings to digital temperature
readouts. See Figure 3-7.
Leak Detectors
Leaks in the refrigeration system will cause the system
to lose its refrigerant charge. Loss of refrigerant will cause
the system not to work properly and could also damage the
ozone layer. In many cases, it is diffi cult to determine the
exact location of the leak as well as how severe it is. Leak
detectors are needed to accurately locate leaks. The vari-
ous kinds of leak detectors are discussed in the following
sections.
Note: Chapter 15 contains more information
on the use of leak detectors.
Electronic Leak Detectors
Using an electronic leak detector is the most accu-
rate way of locating leaks. Electronic detectors use a small
solid state sensor that can detect extremely small leaks. The
detector also has a probe used to draw refrigerant into the
sensor. The probe tip may contain a fi lter to catch oil and
debris. Most electronic leak detectors will make a ticking
noise which increases in frequency as the probe encounters
refrigerant. Large leaks raise the ticking to a high pitched
squeal. Many electronic leak detectors have an LED (light
emitting diode) display which indicates the leak rate. The
detector may use different color LEDs or may progressively
illuminate extra LEDs as the refrigerant concentration
increases. Some electronic leak detectors can automati-
cally determine the type of refrigerant in the system.
A typical electronic leak detector, Figure 3-8, always
uses a small internal battery to power the unit. The detec-
tor will also have an on-off switch, and may contain a
range selector switch to allow for checking large and small
leaks.
To use an electronic leak detector, turn on the detector
switch. Adjust the sensitivity to produce an occasional tick-
ing. Then pass the detector probe end under the suspected
refrigerant leak areas. Since refrigerant is heavier than air,
it will fl ow downward from a leak. If refrigerant is leak-
ing, the detector rate of ticking will increase. Large leaks
will cause a high pitched squeal. When through using the
leak detector, turn the control switch to the off position and
replace the detector in its case.
Figure 3-6. The mechanical temperature gauge shown here is
useful for determining air temperatures at the outlet vents.
Figure 3-7. An infrared temperature gauge gives an accurate
and almost instant temperature reading. (Raytek)
Figure 3-8. Electronic leak detectors are needed to fi nd small
leaks on modern systems. Most detectors can locate both
R-134a and R-12 leaks.