Chapter 6REFRIGERATION AND AIR CONDITIONING
Trouble
Compressor short cycles on
low pressure control.
Compressor runs continuously.
Compressor short cycles on
high pressure control switch.
Compressor will not run.
Possible Cause
Low refrigerant charge.
Thermal expansion valve not
feeding properly.
(a) Dirty strainers.
(b) Moisture frozen in orifice
or orifice plugged with
dirt.
(c) Power element dead or
weak.
Water flow through
evaporators restricted or
stopped. Evaporator coils
plugged, dirty, or clogged
with frost.
Defective low pressure
control switch.
Shortage of refrigerant.
Leaking discharge valves.
Insufficient water flowing
through condenser, clogged
condenser.
Defective high pressure
control switch.
Seized compressor.
Cut-in point of low pressure
control switch too high.
High pressure control switch
does not cut-in.
1. Defective switch.
2. Electric power cut off.
2. Service or disconnect
switch open.
Corrective Measure
Locate and repair leaks.
Charge refrigerant.
Adjust, repair or replace
thermal expansion valve.
(a) Clean strainers.
(b) Remove moirture or dirt
(Use system dehydrator).
(c) Replace power element.
Remove restriction. Check
water flow. Clean coils
or tubes.
Repair or replace low pres-
sure control switch.
Repair leak and recharge
system.
Replace discharge valves.
Determine if water has been
turned off. Check for scaled
or fouled condenser.
Repair or replace high
pressure control switch.
Repair or replace compressor.
Set L. P. control switch to
cut-in at correct pressure.
Check discharge pressure
and reset H. P. control
switch.
1. Repair or replace switch.
2. Check power supply.
3. Close switches.
54.299.2
Figure 6-12.Trouble diagnosis chartContinued.
6-19
