Chapter 6REFRIGERATION AND AIR CONDITIONING
humidistat setting will close the heating switch,
energizing the reheaters.
Proper attention to maintenance checks will
often allow you to detect developing troubles in
time to take corrective action. Since most
breakdowns often occur at the most inopportune
time, periodic checks and maintenance will
prove to be well worthwhile to avoid
The two-position control system can easily be
checked out in a reasonably short time. The
checkout period should be at least every three
months or more often if it proves to be necessary.
Inspection and checks should be conducted at the
beginning of the cooling season and about mid-
way. The same should be done for the heating
Sensing elements should be inspected and any
dust accumulations removed. Thermostatic
sensing elements should have dust and dirt re-
moved with a soft brush, and the sensing elements
in humidistats should be blown off gently with
air so as not to damage the elements.
Magnetic valves should be checked for opera-
tion. Be sure that the valves are opening and clos-
Setpoints of the thermostats and humidistats
should be checked with a calibrated thermometer
and a reliable humidity indicator.
When servicing the two-position control
system there are three possible areas where trou-
ble may occur:
1. The sensing element and its associated
2. The magnetic valves that control the flow
3. The wiring system which connects the sen-
sing elements to the solenoids of the magnetic
valves and the controller of the electric heaters.
Faulty operation of the refrigerating and air
conditioning plants is indicated by various definite
symptoms. Information in figures 6-12 and 6-13
indicates some possible troubles that may be en-
countered, the possible causes of these troubles,
and the corrective action which may be taken. But
remember always consult the manufacturers
technical manual before attempting any repair or
adjustment on your equipment.