Logan Shaw wrote:

Abby Normal wrote:

Rod Speed wrote:

Abby Normal wrote


come back and see me when you figured out how to
get multiple systems to share common duct work rookie.


Dont have to share the same ductwork, ****wit.


okay so you are going to instal 3 systems now, three independent duct
systems


I hate to say it, but I have to concur with Rod on this one. His
style of argumentation leaves a lot to be desired, but in this case,
I agree with his conclusion.

If you are coming off setback and using a secondary heat pump to
do only that, it doesn't need duct work. If it just heats the
air in one room, the primary system will be running continuously
(or nearly) and will be circulating the air around the house
anyway. Even if the secondary heat pump heats the air in one room
up to 95F in the process, eventually that'll even out as the other
system recirculates everything. And heating the air up to such a
high temperature is unlikely anyway, since by definition when
you are recovering from setback, the temperature is colder than
you'd really like it.

However, I do have to admit there could be problems if the secondary
heat pump (that's used only during recovery) is putting heat mainly
into the room with the thermostat. If the temperature in that room
rises faster than in the rest of the house, it could cause the
system to think recovery has finished when it hasn't yet gotten to
that point. And if the secondary heat pump is too far away from
the thermostat, it could cause the system to overshoot the target
and heat up the house too much. But, those are control issues
rather than duct issues, and they seem solvable.

It isn't going to work. If you raise the temp in one room to a point
higher than the desired temp, then you're going to have heat losses
through the exterior walls that wouldn't have occurred with a centrally
ducted system, thus defeating the purpose, at least to some extent. If
you feed it into an interior room then that room will simply get too
hot, no question about it. I hate to say it but it's not a very
intelligent alternative.

hvacrmedic