Heatpump with Propane backup and pellet stove

[irontodd]

Hi there, new homeowner with my first pellet stove. well, and first heat pump.

Previous owners told me that they used the pellet stove down to 30 degrees outside, then let the propane kick in below that. but it's a air exchange heat pump so that doesnt make much sense to me. seems to make more sense to me to use the heat pump down to 30 then let the pellets kick in , and if the pellets aren't pulling the whole weight, let the propane kick in.

right now the heat pump is connected to a Honeywell TH8320 thermostat, and I've locked out the aux heat so it doesn't run on propane until below 30. The stove is a Kozi 100 series, and is connected to its own thermostat (basic 2 wire).

the blower of the stove is directed at the heat pump's thermostat, so I intend to move it, well out of way of the stove output. in considering this move, I thought it would be great to run it all on one thermostat if possible.

the TH8320 is capable of running 3-stage heat, which appears to be what I've got, in my eyes (1. Heat pump, 2. Stove, 3 Propane backup)

I want to use the heat pump blower to distribute heat from stove to the rest of the home, via intake air return ducts. (stove on main floor, heat pump/aux heat in basement)

so I think i need to hook this stuff up as if it were a 3Heat system.
Current Terminal Setup
L - Equipment Monitor
Aux/E - Aux heat (Propane)
Rc/R - Power (Heat pump unit)
O/B - Changeover Valve
Y - Compressor relay
G - Fan Relay
C - 24AC
S1/S2 - Outdoor Sensor

proposed terminal setup
Y2 - to stove ---- this is what I think I need to add
L - Equipment Monitor
Aux/E - Aux heat relay (Propane)
Rc/R Power (one run to heat pump, and one to stove) ---- and this I think i need to add
O/B - Changeover Valve
Y - Compressor relay
G - Fan Relay
C - 24AC
S1/S2 - Outdoor Sensor

would that do what I am hoping?

Thanks In advance,
Todd

 

[DBCOOPER]

If you hook your stove up to y2 you'll send 24 volts from your heat pump control circuit to your pellet stove. Not a good idea. If you hook up a 24 volt relay so the when Y2 calls for heat, the relay will close the stove thermostat circuit. But I think you will be very unhappy with the stove short cycling. The Honeywell stats control real close to set point with very little "swing". Best to keep them on separate stats and do the switch over manually unless your really good with control circuits.

 

[smwilliamson]

You could make an isolated MRB (mechanical relay board) that would control the g wire contact when the stove Tstat closed. I'll find you a link to something similar.


Bravocontrols.com or look up MRB relay in google

 

[smwilliamson]

Here it is, tempcocontrols.com

 

[irontodd]

f you hook up a 24 volt relay so the when Y2 calls for heat, the relay will close the stove thermostat circuit.

DB, is it really as simple as installing a relay? seems simple enough to do so, I understand how relays work, but not so much as to how HVAC work. if I can find another TStat with a wider swing, should be pretty easy to swap that out at a later date if i don't like the Honeywell swing.

but scott's comment about Isolated... would i need to be concerned about Isolating with a simple relay?

I assume (based on the Tstat thats currently on the stove) that I just need to complete a circuit to kick the stove on.

if i'm thinking about it correctly i think i'd need to hook the Y2 to the energizing pole of the relay coil, and the other end of the coil to ground (back at the heat pump control board). the other two NO points on the relay would hook to the stove terminals.

 

[DBCOOPER]

if i'm thinking about it correctly i think i'd need to hook the Y2 to the energizing pole of the relay coil, and the other end of the coil to ground (back at the heat pump control board). the other two NO points on the relay would hook to the stove terminals.[/quote]

A relay does isolate the different control circuits. You are thinking about it correctly Y2 to the relay coil and ground and no contacts to the stove.

I don't know what your paying for propane (its pretty cheap around here this year) or electricity but if I had propane for a backup to my heat pump I would only burn my pellet stove for ambiance this year.