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Abe
10-01-2002, 09:14 PM
Wondering if any members have come across a condenser fan controller on a Williams Freezer Walk In Room outdoor unit.

I say "controller" because Im not sure its a fan speed controller, which rather modifies the speed of the fan motor.

This controller cuts the power to the fan when the temperature of the coil reaches certain limits.

My question is, how does it work? and whats it supposed to do.
The marking on the controller has a knob which can be turned between 30 c and 60 c.

controller has a probe/sensor which is located at the bottom of the condenser coil.

Are these units prone to failure?
How do I test it? Or should I just replace?

Thank you

subzero*psia
11-01-2002, 02:42 AM
Sounds like a thermistor or pressure sensor... either one would work since there is a P/T relationship. The control may lower the voltage to the motor, like a potentiometer, causing the motor to run lower rpm's? Are there any other electronic parts wired in series with it?

Abe
11-01-2002, 11:16 PM
Hi sub,

Thanks,

No link to any electronic panel or component.
Works just like a switch, probe senses temp and cuts power to fan.

Ive linked fan directly to run with compressor
So far so good, everything working hunky dory

pss.. Wonder why OEM put this pesky controller in first place, I think it is designed to prevent over condensing of refrigerant during very cold ambient conditions

Ill ring Williams first thing Monday, so will keep you informed what this thingy is

subzero*psia
12-01-2002, 01:02 AM
What type of metering device is used on the evaporator? It would only seem sensible if it were on a captube system... even then why not run full rpm's?? I can see if the ambient temp were to fall too low... slow the fan to maintain an efficient compression ratio.

Some folks keep systems in areas where the temp drops dramatically in winter... they either have to restrict airflow, slow fan motor speed or use a headmaster. Perhaps this system you are describing slows the motor as the temperature drops... if the ambient is low and the fan runs normal speed, the liquid would back up in the condenser causing a high subcooling which would trip the switch to lower the motor speed and increase head pressure... but I would think you would need another sensor for the ambient as well. Otherwise what would it base the TD on?

Are you sure it is OEM... maybe a tech accidentally wired a high pressure cut-out to the fan motor instead of the compressor! LOL!! LOVE THEM COWBOYS... YEEHAAA! I shouldn't say that... I have done some really stupid things too... sometimes just by opening my mouth! LOL!! YEEHAAA! :p

Gary
12-01-2002, 03:21 AM
Actually, maintaining a minimum liquid temp leaving the condenser in low ambient might make sense. The head pressure should follow it pretty well.