Defrost Control Concept
• Defrost Control is heat output for
electric and hot gas systems to prevent build-up of frost
•
Manual or automatic defrost setpoints – Time – Temperature – Pressure
• Setpoints control initiation and
termination
•
Initiated defrost heats coil
• Disables fans until termination setpoint
is met
Troubleshooting Error Messages •
E1
Not in program mode – If the E1 message appears when no keys are being pressed,
replace the control.
• E2 Settings are not properly stored in
memory – Check all settings and correct if necessary.
• EP Probe is open, shorted or sensing a
temperature out of range – Check to see if the sensed temp is out of range. If
not, check for probe damage by comparing it to a known ambient temp between -
30° F and 220° F. Replace the probe if necessary.
• EE EEPROM data has been corrupted – This
condition cannot be field repaired. Replace the control.
• CL Calibration mode – Remove power to the
control for at least five seconds. Reapply power. If the CL message still
appears, replace the control.
Meat Refrigerated Counter
Troubleshooting Defrost Timers Purpose Of
The Timer
•
Shut off the refrigerator's compressor and evaporator fan motor
• Turn on the defrost system at regular
intervals to rid the evaporator of frost How They Fail
•
Timer motor, motor bearing, or reduction gears wear out
• Occasional or constant noise comes from
the part
• Runs sometimes but not others, causes
occasional frost to build up gears jam or bearing piles up, timer stops
rotating
• Motor coil burns out and becomes an open
circuit, timer stops rotating
• Burnt out contacts stick together
If timer stops, different situations will
occur: Stops in run cycle
• Refrigerator fails to automatically
defrost
•
Evaporator builds up with frost and restricts air flow Stops in defrost part of
the cycle
• Food in the freezer thaws
• Refrigerator components do not operate
Why do I need a Defrost Control?
• Ice is a great insulator
• Frost build-up on evaporator coil makes
it less efficient
• Defrost control will determine when to stop
the cooling to allow the frost and ice build-up to thaw
• Decision is based either on a time
schedule (defrost timer) or a precise reading of the temperature or pressure of
your equipment (defrost control)
