On Jan 20, 5:50*pm, The Daring Dufas the-daring-du...@stinky-
finger.net wrote:
On 1/20/2013 1:14 PM, Ernie wrote:





" wrote:

The most inexpensive residential AC systems lack a factory
installed head pressure control which is why it's not prudent
to run them in cold weather.

Why couldn't a thermostat that can sense condenser coil temperature
be used to turn on the fan when the coils reach some pre-determined
temperature?

Because it's not needed and just one more thing to fail
and would then need to be serviced. *As for the AC being
damaged by operating it lower than 60F, personally I
think it's BS.

I don't think the AC would dammaged by low-temperature operation, but
clearly the efficiency of heat-transfer would be affected if the
operation of the condenser fan resulted in insufficient line-pressure in
the evaporator line.

This would explain why most residential AC units don't seem to cool a
house very well when ambient outdoor temperatures reach "room
temperature".

Believe me, running an AC unit during periods of very low ambient
outdoor temperatures CAN and WILL cause damage to the compressor unless
steps are taken to control head pressure in the system.

And that is like 59F? The claim was made that it can't
be run below 60F outside temp.




The refrigerant
can migrate to the compressor crankcase causing liquid slugging of the
compressor which is supposed to pump vapor not liquid. That why most
systems have a crankcase heater to keep the compressor warm to prevent
the majority of the refrigerant charge from winding up in the
compressor.

A residential AC doesn't. That's what was being discussed.
And if it's such a threat to destruction, why don't they have
a lockout that prevents it from running at 50F? Would seem
there would be a lot of AC systems shot from say a kid
or someone accidently turning it on under those conditions,
no?




One of the things I do for a living is servicing and
repairing refrigeration and air conditioning equipment. ^_^

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