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Cooler/Freezer Diagnostic Protocol Cheat Sheet (DRAFT) by [deleted]

Diagnosis Problems in Coolers/Freezers

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Mainte­nance Helps Avoid Energy Waste & Repairs

Operations and mainte­nance issues should be addressed to avoid excessive energy use and costly repairs, as well as potential product loss. Additional mainte­nance issues can be reviewed in the Walk-in Cooler­/Fr­eezer Diagnostic Protocol table shown below.
Credit: Eric Borchardt, EIT, LEED AP, is an energy engineer for Michaels Energy,

Diagnosing Problems

Possible Cause
Power is on, but control board does not display.
1. Phase loss or fuse blown.
2. Power phase open or transf­ormer shorted.
3. Control board failure.
1. Check wiring for breaks and replace fuse.
2. Check Transf­ormer output voltage (12V)
3. Replace cold storage room control board.
Control board displays, but compressor does not run.
1. Compressor relay tripped.
2. Hi-Lo pressure safety switch shut down.
3. Defective contactor or coil.
4. Cold room temper­ature is lower than operation setpoint.
5. Internal thermal overload tripped.
6. Compressor malfun­ction.
1. Determine reason and take correct action.
2. Determine type and cause of shutdown and correct it before resetting safety switch.
3. Repair or replace.
4. Reset operation temper­ature setpoint.
5. Wait until compressor cools down for reset.
6. Check compressor motor winding.
High discharge pressure
1. Dirty Condenser coil.
2. Fan not running.
3. System overch­arged with refrig­erant.
1. Clean walk-in cooler and walk-in freezer condenser coils.
2. Check fan motor and its electrical circuit.
3. Reclaim excess refrig­erant.
Low discharge pressure.
1. Insuff­icient refrig­erant in system.
2. Low suction pressure.
1. Check for leaks; repair and add charge.
2. See corrective steps for low suction pressure.
High suction pressure.
1. Excessive load.
2. Expansion valve overfe­eding.
1. Reduce load.
2. Regulate superheat.
Low suction pressure.
1. Lack of refrigerant.
2. Plugged suction filter.
3. Evaporator dirty or iced.
4. Fan not operating.
5. Expansion valve underf­eeding
1. Check for leaks. Repair and add charge.
2. Replace suction filter.
3. Clean and defrost.
4. Check fan motor and circuit control.
5. Regulate superheat.
Large difference between actual cold storage room temper­ature and set point on control panel
1. Incorrect room temperature.
2. Sensor placement, wire too long.
3. Sensor contactor open.
1. Re-pos­ition sensing point of temper­ature sensor.
2. Enlarge wire section.
3. Reconnect sensor.
Heavy frost builds up on evaporator fins High temper­ature alarm.
Too much time between defrost cycles or incomplete defrosts.
Manual defrost and adjust defrost cycle
1. Overload and door open excessively.
2. Bad refrig­eration performance.
3. Heavy frost build-up on evapor­ator.
1. Reduce load and door opening.
2. See corrective steps for discharge and suction pressure malfunctions.
3. Manual defrost and adjust defrost cycle.
Coil not clearing off frost during defrost cycle.
1. Heater malfunction.
2. Not enough defrost cycles per day.
1. Check heater operation.
2. Adjust defrost control.
Ice accumu­lating in drain pan
1. Heater malfunction.
2. Not enough defrost cycles per day.
1. Check heater; replace if necessary.
2. Clean drain line.
Display screen flashes, unit emits humming noise.
Observe alarm indicator.
See alarm indicator for remedy.