Emergengy heat?

[Mac Sidewinder]

I have a Trane heat pump furnace that has an emergency backup heat option that uses propane gas. This is run off a Trane XT500c thermostat. I also have a Classic Bay 1200 free standing pellet heater that runs off a Honeywell Lux 110 thermostat. When it gets too cold for the heat pump to keep up (around 32 degrees) we usually turn on the pellet stove (since this is the cheaper option than the emergency heat burning propane gas). But having the pellet heater on all the time is not cheaper than the heat pump only working. Here is what I would like to do...


I would like the heat pump to be the main heat source. When it can't keep up I would like the pellet stove to assist automatically. The two ways I can see this happen are:


1. Use the emergency signal from the Trane thermostat to control the pellet stove instead of the propane heater. I believe the signal from the Trane thermostat is on the X2 wire. Can I disconnect this wire and hook it to the thermostat wire going to the pellet stove? OR

2. Can i disconnect the emergency wire from the Trane thermostat (leaving it disconnected) and set the Lux thermostat for the pellet so that it comes on automatically when the heat pump can't keep up?

I am not very informed on how heat pumps work. I read on another site that besides calling for emergency assistance (via propane heaters) the emergency wire also is used for some kind of defrosting of the condensor unit? If I disconnect this wire will this harm my condensor?

The wire colors on the Trane are as follows:

Terminal - Wire color

B ---------- Blue

R ---------- Red

W ---------- White

Y1 ---------- Light Green

X2 ---------- Light Blue

O ---------- Red with Black stripe

G ---------- Green

The wire colors on the Honeywell Lux 110 for the pellet stove are both white (since I believe this is a simple switch connection type).

Also is there a way for the blower fan on the furnace to automatically come on while the pellet heater is functioning? I thought this might help circulate the warm air, or would this simply be pushing cold air out of the basement through the house?

Any assistance or other ideas would be appreciated. Thanks

Mac

 

[DMKNLD]

Also is there a way for the blower fan on the furnace to automatically come on while the pellet heater is functioning? I thought this might help circulate the warm air, or would this simply be pushing cold air out of the basement through the house?

Any assistance or other ideas would be appreciated. Thanks

Mac

Unfortunately I can't help you Mac on your heat pump / Quad CB interface issue - definitely above my pay grade.

But RE using your furnace blower to help circulate the pellet stove warmed air - if the furnace or central AC system is on the same floor level as your pellet stove it will work well. But if your furnace is in the basement, like mine is, then it will just draw the warm air down the cold air ducts and cool it to closer to the basement temps before sending it up the floor vents.

 

[Arti]

I don't know the specs on that particular thermostat, However it is possible that your Trane dealer can install a thermostat with 3 stages of heat. 1st stage would be heat pump, 2nd stage pellet stove, 3rd stage lp. Most likely you will need an isolating relay to make this work, It's not a good idea to mix control wire voltages from 2 different stoves.

Most heat pumps are setup to kick in the backup heat when the heat pump is defrosting when the heat pump is done it turns off the backup heat. The problem is that by the time that the pellet stove gets lit and producing heat the heat pump would turn it off !!

 

[DBCOOPER]

How much are you paying for propane? When the heat pump goes into defrost it reverses the Freon loop and puts it into air conditioning mode and pumps heat from the house thru the Freon and it melts the ice build up from the condenser coils. The emergency heat or stage two heat comes on to overcome the cold air that that is generated in this mode. It usually comes on based on time but newer units base it on actual conditions. so if you pull the stage two wire you'll get cold air when it goes into defrost. If you use this wire to control the pellet stove it will start the stove every time the heat pump goes into defrost. Emergency heat mode locks out the compressor and only uses the back up heat. You can do what you want to do but you need to be good with control circuits and wiring. What I did was build a circuit that that switches between heat pump and Quad CB1200i based on outdoor temperature.

 

[DBCOOPER]

 

[DBCOOPER]

 

[DBCOOPER]

I made it pretty complicated with backup if the stove doesn't function for some reason, like running out of pellets.

 

[Mac Sidewinder]

Thanks for the info DBCOOPER. I wonder if I can just simplify this alot by just turning off the propane gas at the furnace. Set the pellet stove a couple degrees lower than the furnace. Then when the heat pump can't keep up the pellet stove would turn on? From your description of the defrost mode of the heat pump I take it that only the heat from the house is needed to defrost the coils and no propane gas is needed? Any drawbacks to this? I just want to be sure that I don't hurt my heating system.

The whole reason for all this is that where I live we have to buy propane contracts a year in advance and right now we are under contract for propane at $1.80 a gallon. I have plenty of pellets (3 tons) and I would rather use as little propane as possible until the next contract date.

Mac

 

[Arti]

Turning off the Gas will make the furnace not light however it will still try to light, putting stress on the ignition system. Some furnaces have an interlock in them so if there isn't any gas pressure it disables the heating system, this is common in lp furnaces not so much with natural gas.

 

[DBCOOPER]

How new is your heat pump? Is it a variable speed newer one? I think your best bet would be to control it manually. The reason I went through all the trouble of wiring mine up was when it got warmer during the day I would still be burning pellets when the heat pump could do it more efficiently not the other way around. Plus my back up is electric at .18 a KWH.
Instead of turning off the gas, you could put a switch in the wire for your back up heat, I think it would be W2, and that way the thermostat could not call for back up heat if the switch is open. If I had a high efficiency heat pump with propane backup @ $1.80 a gallon my stove wouldn't be on that much.

 

[Mac Sidewinder]

Thanks for all the info guys - The heat pump seems to be able to keep up as long as its over freezing. I guess I will just shut it down on the times that it goes below and then turn on the pellet stove. I was just looking for someway to make it more automatic I guess.

Bill

 

[JDenyer236]

This should be easily doable. I would use relays and an outdoor temp probe to control things When temp is below 32F a relay closes and fires up the pellet stove. When the temp is above 32F this same relay opens and another closes allowing heat pump operation. You can get relays in various configurations that will allow you to do want you want from one relay box.

 

[JDenyer236]

Here is a very crude sketch of what you could do, basically relay 1 breaks the 24 volt control circuit to the heat pump at cold temps, and makes the circuit for the pellet stove at the same time, the reverse would occur at warmer temps. Because the pellet stove is millivolt you would not need 24 volts in that circuit, just 24 volts to the relay input to power the relay You may need 2 temps sensors to accomplish this. Like I said this was just a quick sketch so you would need to tweak it to the components that you use.