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Re: commercial fan on evaporator cuts off after starting
There is an overheat klixon on the evaporator that stops the fan running until the coil gets below -11c This can take some time after startup. if the freezer runs more than an hour before the fan starting, check the klixon isn't faulty, and you have power to the fan. Also check the condenser grille is nice and clean as it will slow down the freezing process.
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The unit needs two fans running and good airflow, one fan outside cools the condensor coil and the other inside the unit blowing across the evaporator coil, warming it. The compressor must start up. The defrost timer stops everything and switches on a heating element to defrost the evaporator for several minutes. Please verify these conditions. The condensor coil may get clogged with dirt and lint, the evaporator may get clogged with ice build up, or the fan may quit working due to bad bearings, need for lubrication, or burn out. The defrost timer has an internal motor and contacts which may quit working, some have a way to manualy turn it to switch its mode in case it quits working.
The unit needs two fans running and good airflow, one fan outside cools the condensor coil and the other inside the unit blowing across the evaporator. The compressor must start up. The defrost timer stops everything and switches on a heating element to defrost the evaporator for several minutes. Please verify these conditions.
Check the defrost timer (in the base, circular knob you can turn till it clicks) If it doesn't heat up rapidly in the evaporator, there is a safety overheat device (thermistor) that may be cutting power to the heater, or there may be a fault with the heater itself. Are you sure the fans are working, and the condenser grill is nice and clean?
Could be a number of things. It has a thermistor that sits on the evaporator to keep the fan off until it gets cold. It also has a switch above the door that switches the fan on when the door's closed. It could be a loose connection in the wiring, or, lastly, it could be a seized fan
The defrost termination/ fan
delay control is a temperature-activated, single pole-double throw
switch. ). The control is wired into the
refrigeration circuit. The control is located high
on the evaporator where the frost is likely to clear last. The function
of this temperature-activated switch is to terminate defrost when the
evaporator coil has been defrosted, and to delay the evaporator fans
from coming on immediately after defrost. The coil must reach a temperature of 25* F. for the fan delay to close allowing the fans to operate.
Most all commercial freezers like yours have, what is called, a fan delay. It is located in the evaporator case and is usually attached on or very close to the actual cooling coil. It may also be a combination switch known as a defrost terminator/ fan delay. It's purpose is to keep from circulating warm air. If the cooling coil does not reach a preset temp, the fans do not come one. Another thing is that the fan motor may just be bad. If you have more than one fan, then chances are that it's going to be the fan delay. I would start there to see that either the fan delay switch is bad or there is a reason that the coil is not getting cold enough to activate the switch.