RP wrote:
Rod Speed wrote:

RP wrote:

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.


Corse it'll work.


If you raise the temp in one room to a point higher than the
desired temp,


That isnt going to happen when the secondary system is
JUST used to come off the setback in a reasonable time.


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.


Nope.


If you feed it into an interior room then that room will simply get
too hot, no question about it.


Wrong again.


I hate to say it but it's not a very intelligent alternative.


Corse it will work fine. No reason why the secondary system
cant have a slightly lower than normal temperature set so it
recovers from the setback in a decent time and then stops and
leaves the primary system to get the temp back up to normal.
Thats going to happen fine since the temp difference is well
within its capabilitys.

Supposing that I grant your every point, what would be the point of such a
system?

It makes setback viable with a heat pump.

Wouldn't it be much easier to simply install a larger staged system?

Nope, and likely quite a bit cheaper not to too.

If there was not going to be anyone in the house during the day,
I'd personally run the setback right thru to the afternoon and
have the system come back off setpoint at a time that would
ensure that it was back to normal temp by the time everyone
came home again and thru the evening. Go back onto setback
after everyone has gone to bed.