In article ,
Jon Elson wrote:
:Pete C. wrote:
:
: No, it isn't. It was documented on a well monitored high efficiency
: model home where the backup heat strips on the high efficiency heat pump
: were kicking in in order to provide a reasonable temp recovery time
: since the heat pump itself did not have the capacity. The electricity
: used during the temp recovery was more than would have been used on temp
: maintenance due to the switch to lower efficiency backup (100% vs.
: 300%+).
:
:OK, this is a killer example, where the furnace efficiency goes down the
:tubes when it needs to raise the temp suddenly. It might be possible to
:stage the temp rise to avoid that with a suitable thermostat.
:
:But, many other heating systems have no such penalty for a rise in temp
:setting, such as a traditional gas forced-air furnace.

My gas furnace is 2-stage, and not particularly exotic (a common Trane
model, 80,000 BTU). Presumably it's more efficient when operating on
low-heat, as otherwise there's little point in the added complexity of a
2-stage burner and control. Except in really extreme weather, the only
time it runs on high-heat is during recovery from night time setback.

--
Bob Nichols AT comcast.net I am "RNichols42"