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Posted by Brian on July 20, 2005, 12:01 am
>Brian wrote:
>> Problem (I think)
>>
>> I have a 3000 S/F ranch with central A/C. The A/C is controlled by the same
thermostat as my heat.
>> It's the standard issue Honeywell t-stat, round with A/C and Fan switches at
the 11:00 and 2:00
>> positions. Heres the thing thats strange. When I set the temp to say 80,
the A/C comes on but
>> doesn't shut off until the temps down around 70 - 72. This is according to
the thermometer on the
>> t-stat, as well as a digital thermometer I have on the other side of the
room. This same t-stat is
>> spot on in the winter months when used for heat. Why is there such a wide
swing in tempurature on
>> A/C but not with heat ???? When I pop the cover off the t-stat there looks
to be an adjustment
>> pointer on the bottom. what does this adjustment do ???? I'm stumped
here..... Thanks for the
>> help....
>Possibilities:
>1) The t-stat is out of calibration. What does the temperature rise back
>up to before it calls again for cooling?
It rises back up to the set temp before it comes back on.
Whats that slide adjustment thing on the bottom of the t-stat ????
>2) The t-stat may have a worn-out bimetal (that's the ribbon spring
>looking thing behind the bulb assembly). No problem in heat mode
>because it wasn't bad during winter.
Actually, this problem started at the end of last summer but I had forgotten
about it. The heat was
ok this winter though.
>3) Short, causing current to flow through the heat anticipator or
>cooling compensator during call for cool. This will fool the t-stat into
>thinking its warmer inside than it is.
>This is a typical problem in older Honeywell rounds when they pass about
>20 years in age. How old is this stat?
Just about 20 years old............. Now i'm noticing it's 12 degrees colder
than it's set for
and the A/C is still running........ Maybe it's time for a digital
t-stat............. Are they
any good ????
>In any case the t-stat seems to be the defective component. There are
>other possibilities, but most would cause erratic cycling which you
>didn't report. Given that this is a common fault for this t-stat odds
>are its due for replacement. HTH.
>hvacrmedic
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> I have a 3000 S/F ranch with central A/C. The A/C is controlled by the same
> thermostat as my heat.
> It's the standard issue Honeywell t-stat, round with A/C and Fan switches at
> the 11:00 and 2:00
> positions. Heres the thing thats strange. When I set the temp to say 80, the
> A/C comes on but
> doesn't shut off until the temps down around 70 - 72. This is according to
> the thermometer on the
> t-stat, as well as a digital thermometer I have on the other side of the room.
> This same t-stat is
> spot on in the winter months when used for heat. Why is there such a wide
> swing in tempurature on
> A/C but not with heat ???? When I pop the cover off the t-stat there looks to
> be an adjustment
> pointer on the bottom. what does this adjustment do ???? I'm stumped
> here..... Thanks for the
> help....
> Brian