Robert11 ) said...

Hello:

A bit confused over the terminology on furnace thermostats.
Embarassed to ask, but really want to be sure I have it right.

Does a 2 stage furnace (where there are two gas valve settings; a high heat
and a lower heat output) require a 2 stage thermostat ?

Maybe in some cases, but I have a Carrier two stage furnace with a normal
thermostat. When the thermostat calls for heat, the 60,000 BTU burner
comes on. If the thermostat is not satisfied (meaning, the room temperature
has reached the setpoint) within a certain amount of time, it automatically
shifts to the "second stage" which means a second burner fires up to
provide a total of 100,000 BTU.

Only on the coldest of days is the the full 100,000 BTU actually needed.
There's probably a very small, if any, fuel savings since theoretically
the house still has to be heated to the same temperature relative to the
outside temperature. Losses due to inefficiency would be lower with the
lower stage burner, so some fuel savings is possible.

It does improve comfort on the days that are not the coldest. On these
days, instead of more frequent temperature swings from the full power
coming on and heating up the home in a shorter time and shutting off,
the lower stage can do a better job of regulating the temperature.

--
Calvin Henry-Cotnam
"Never ascribe to malice what can equally be explained by incompetence."
- Napoleon
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