SERVICE AND ANALYSIS
REFRIGERATION
CHART
SYSTEM
MALFUNCTION
POSSIBLE CAUSE
SOLUTION
Compressor will not start - no hum
1. Line cord not plugged in.
1. Plug in the cord.
2. Fuse removed or blown.
2. Replace fuse.
3. Overload protector tripped.
3. Refer to electrical section.
4. Temp control stuck in open position.
4. Repair or replace temp control.
5. Wiring improper or loose.
5. Check wiring against diagram.
Compressor will not start - hums but
1. Low voltage to unit
1. Determine reason and correct
trips on overload protector.
2. Relay failing to close
2. Determine reason and correct, replace
if necessary
3. Starting capacitor defective.
3. Determine reason and replace
4. Improperly wired.
4. Check wiring against diagram
Compressor starts but does not switch
1. Low voltage to unit.
1. Determine reason and correct.
off of start winding.
2. Relay failing to open.
2. Determine reason and correct, replace if
necessary.
3. Run capacitor defective
3. Determine reason and replace.
4. Comp Mt winding is open or shorted
*4. Determine cause. correct, and replace comp
Compressor starts and runs, but
1. Additional current passing through
1. Check wiring diagram. Check for added fan
short cycles on overload protector.
overload protector.
motors, pumps, etc. connected to wrong
side of protector.
2. Low voltage to unit.
2. Determine reason and correct.
3. Overload protector defective.
3. Check current, replace protector.
4. Run capacitor defective.
4. Determine reason and replace.
5. Excessive discharge pressure.
*5. Check ventilation, restrictions in cooling
medium, restrictions in refrigeration system.
6. Compressor too hot - return gas hot.
*6. Check refrigerant charge (fix leak if
necessary). Check air flow across condenser.
Unit runs OK, but short cycles.
1. Overload protector.
1. Check wiring diag for correct wiring
2. Cold control.
2. Differential set too close.
3. Overcharge.
*3. Reduce refrigerant charge.
4. Air in system.
*4. Recover and recharge.
5. Undercharge.
*5. Fix leak and recharge with refrigerant.
Unit operates long or continuously.
1. Dirty condenser
*1. Clean condenser
2. Shortage of refrigerant.
2. Fix leak, add charge, correct charge
3. Temp control contacts stuck or frozen
3. Replace Temp control
4. Evaporator coil iced.
*4. Defrost
5. Restriction in refrigeration system.
5. Determine location and remove.
Start capacitor open, shorted or blown.
1. Relay contacts not opening properly.
1. Replace relay
2. Low voltage to unit.
2. Determine reason and correct.
3. Improper relay.
3. Replace.
Run capacitor open, shorted or blown.
1. Improper capacitor.
1. Determine correct size and replace.
2. Excessively high line voltage
2. Determine reason and correct.
(110% of rated max).
Relay defective or burned out.
1. Incorrect relay.
1. Check and replace.
2. Line voltage too high or too low.
2. Determine reason and replace.
3. Relay being influenced by loose
3. Remount rigidly.
vibrating mounting.
Space temperature too high.
1. Control setting too high.
1. Reset control.
2. Overcharged with refrigerant.
*2. Recover refrigerant and recharge with
proper charge specified on dataplate.
3. Inadequate air circulation.
3. Improve air movement.
Cooler freezing beverage.
1. Temperature control
1. Reset control.
Unit noisy.
1. Loose parts or mountings.
1. Find and tighten.
2. Tubing rattle.
2. Reform to be free of contact.
3. Bent fan blade causing vibration.
3. Replace blade.
4. Fan motor bearings worn.
4. Replace motor.
LAB
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RepCo
101 Witmer Road, Suite 700 • Horsham, PA 19044
Phone 1-800-521-0754 • Fax 215-442-9202
www.labrepco.com • [email protected]
