An old mercury thermostat had to be set to allow a little temperature
drift to prevent short cycling. An electronic thermostat can be
programmed with a timer as well to prevent short cycling, so it can keep
tighter temperature control (that is, if it is in "cool" mode, and the
temperature rises quickly after the A/C shuts off, a mercury stat will
wait until the temp. rises 3 degrees or so to kick back on. The
electronic will kick on as soon as the temp rises past its threshold -
probably less than a degree - but will not actually turn the A/C on if
not enough time has elapsed since the A/C shut off. It'll wait 2-3
minutes to let the compressor unload and then let it start.

nate

allanc wrote:
Yes, I remember my parents house was oil heated and had a round
thermostat.
I think that it allowed a 2-3 variance.
But, that may have been part of the design of the thermostat.

On Sep 11, 11:17 pm, "Art" wrote:
Most electronic ones keep the house temperature much more stable than an old
mechanical one so even if you don't want to program it it is worth
switching.

Follow the instructions when changing it out. Specifically mark the wires
with labels indicating what they were attached to on the old thermostat so
you can hook them up to the new one.

"allanc" wrote in message

...
On Sep 11, 10:41 pm, "Bob M." wrote:

"allanc" wrote in message
...
It's a mechanical type.
I will take the cover off tomorrow in the daylight and try to get the
model number.
The unit is probably decades old.
Do you think the manual would actually have troubleshooting tips such
as when the temperature is off by 8 degrees?
Mechanical thermostat? Don't bother fixing it. Get a programmable
electronic one & save big money.
Someone once told me that in his opinion, there was a point of
negative return.
For example, in the winter, if you turn down the temperature *too* low
at night, the cost of warming the house to the daytime temperature
would exceed the savings that you obtained at night.

Comments?


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