On Tue, 20 Dec 2005 18:43:51 GMT, "Dr. Hardcrab"
wrote:


wrote in message
roups.com...
I have a Lennox Heat Pump and a Honeywell Chronotherm IV 8611
Thermostat. I understand the concept of the heat pump. I am a little
confused about the Auxilary electric heat though. I live in Connecticut
and it's been ranging from 2F to 20F degrees at night. I have the
thermostat set at 65F. Some nights the unit runs almost constantly. I
had a service call yesterday and the tech said this is normal in the
winter. He checked the Auxilary heat and it does work. He explained
that it is only supposed to come on if the temperature is 2 degrees or
more from the target temperature. If this is the case it seems to me
that the Auxilary heat would NEVER be used as the heat pump itself will
activate as soon as the temperature falls 1 degree below the setting.
My question is does the Auxilary heat work by temperature or should it
help the heat pump reach the desired temperature if it knows it will
take an hour to get back to the deired temp. If I set the temperature 2
degrees or more higher the Aux heat kicks in, but if I leave it at 65
constantly it never comes on regardless of the outdoor temp. Is this
normal?? I just want to make sure it's working the way it's supposed to
be! Thanks for any advice!

It's normal.

If it is getting down to the low teens/single digits, it WILL run
constantly. Hopefully the aux heat will cycle and not run constantly
too.....


That's true, but you're wasting a lot of energy melting the ice off
the outside unit during the defrost cycle.

I live in western NY, so have similar or colder temps than Connecticut
in the winter. We have a similar heat-pump/electric-furnace system,
with a Chronotherm III.

When it gets that cold out, I switch the thermostat to "emergecy
heat", which disables using the heat pump and just uses the furnace
(auxiliary heat). This is as efficient (probably more efficient) than
the heat pump at these temperatures. That's because a) the heat pump
inherently gets less efficient as the temperature difference becomes
greater, and b) to avoid ice build-up on the outside unit, the system
has to run a defrost cycle. In the defrost cycle, the system runs
backwards (essentially in air conditioning mode), to heat up the
outside unit and melt off any ice. Similar to defrost in a freezer.
All that energy is wasted of course, as you're literally heating the
outdoors.

One thing to watch out for if you stay in emergency-heat mode for a
long time. Snow and ice can build up on the outside unit. When you
switch back to heat pump mode, the fan may not have any place to push
the air to. So you may need to go outside and brush off the unit. (If
you're running the heat pump all the time, the fan being on keeps the
snow and ice from building up.)

Terry