Quoth Carl:
>Most window air conditioners have a little sticker next to the
>controls: "Do not turn on until this unit has been off for three
>minutes."
>Why not? What happens if you turn it off, then on again one minute
>later?
******
You're supposed to give the AC's refrigerant system a few minutes to equalize.
Y'see, the refrigerant (let's just say "Freon", o-tay?), in a gaseous state, is
compressed by the, uh, compressor. It travels to the condenser (located at the
OUTSIDE end of the AC) where the gas is cooled (subcooled, more like it),
forced thru an itty-bitty capillary tube, and goes on to even more adventures.
But, you didn't ask for the rundown on how the AC *works*, just WHY you should
give it that 3 minutes.And here it is:
In an AC that has been off for more than 3 minutes, the pressure of the Freon
at any one point in the closed refrigeration system is equal to the pressure at
any other point. "Equalized", in other terms. To start up the AC's compressor
at this state of equalization is nice'n'easy on the comp's motor.
However, after the unit has been running awhile, there is the differential in
pressure that I spoke of. If you try to turn the AC "on", the compressor's
motor cannot begin to turn before it draws so much "locked rotor" current
(amps) that your circuit breaker trips. Keep this up, and the compressor will
burn out.
In most AC's, there is a device known as a "thermal overload" that senses the
extra current being drawn by the compressor. The TO, being a bimetal switch,
heats up, and disconnects the compressor from the line. The bimetal cools down
after a few minutes, pops back into place, reconnecting the line. The
compressor tries to turn on, and it either indeed does turn on, or if the
pressures haven't yet equalized, the TO will kick out, only to reset in another
few minutes. You can demonstrate this for yourself by:
a) Run your AC for about 5 minutes
b) Turn the THERMOSTAT control down until you hear the comp stop running (just
the blower fan will be going now)
c) Wait 3 seconds, then turn the THERMOSTAT control up to whatever setting it
was at before.
You will hear the compressor groaning as it tries to overcome the unequal
pressures, then it will stop groaning as the TO kicks out.
After a few minutes, the TO will reset, and the comp will try again.
The TO, which costs the AC manufacturer about 95 cents, isn't designed into
all ACs (I wonder why not?). But a lot of Mfg's mold the words "Wait 3 minutes"
onto the units that actually HAVE a TO. Here it saves the cost of having to
mold the line on some plastic grilles, but not on others.
regards,
Keith (And the warrantee is VOIDED if you fail to keep the AC free of
NEMATODES, too) G
<This sentence is a palindrome emordnilap a si ecnetnes siht>
