Anyone doing dual-fuel heating systems?

[Sendero]

I just got A/C installed and decided to go with a heat pump instead of just an A/C unit. The interesting part of it though is that at certain temperatures I need to have the system switch over to use the gas furnace for heating instead of the heat pump. I have an RCS TR40 thermostat so that I can integrate with the ELK. problem is, it does not support dual fuel systems and switching over like that. I talked to RCS and they confirmed that

They did suggest that I may be able to use a relay or two, integrated with the ELK to setup the system to switch over to the furnace based on a temp probe. They did say that they had heard of people doing this both automated and just with a manual switch.

So, is there anyone on here that has setup a dual-fuel heating system or has some advice on how to go about doing it? I'm thinking I'm probably fine with a manual cutover b/c the only time I really need to switch to furnace heat is when the temp is below 40 degrees (maybe even lower), and I'd be happy to just use the furnace alone at certain times of the year. If anyone can help out with their own setup and/or some wiring diagram info I would greatly appreciate it. The system is up & running now with the heatpump providing both heat & cool, but by next November or so I'll need to be able to switch over.

 

[DavidL]

My home is heated with a geothermal primary and propane secondary furnace. The TR40 is setup in HeatPump mode and kicks in the propane when there is too much temp drop for the geo to keep up. In the summer, the change over signal from the thermo trips a relay that turns on the A/C system and not the heating system.
Is this what you were interested in?

I just got A/C installed and decided to go with a heat pump instead of just an A/C unit. The interesting part of it though is that at certain temperatures I need to have the system switch over to use the gas furnace for heating instead of the heat pump. I have an RCS TR40 thermostat so that I can integrate with the ELK. problem is, it does not support dual fuel systems and switching over like that. I talked to RCS and they confirmed that

They did suggest that I may be able to use a relay or two, integrated with the ELK to setup the system to switch over to the furnace based on a temp probe. They did say that they had heard of people doing this both automated and just with a manual switch.

So, is there anyone on here that has setup a dual-fuel heating system or has some advice on how to go about doing it? I'm thinking I'm probably fine with a manual cutover b/c the only time I really need to switch to furnace heat is when the temp is below 40 degrees (maybe even lower), and I'd be happy to just use the furnace alone at certain times of the year. If anyone can help out with their own setup and/or some wiring diagram info I would greatly appreciate it. The system is up & running now with the heatpump providing both heat & cool, but by next November or so I'll need to be able to switch over.

 

[Sendero]

My home is heated with a geothermal primary and propane secondary furnace. The TR40 is setup in HeatPump mode and kicks in the propane when there is too much temp drop for the geo to keep up. In the summer, the change over signal from the thermo trips a relay that turns on the A/C system and not the heating system.
Is this what you were interested in?

No, not quite. close though. How does your thermostat know when to not even both trying the geo system? For a heat pump, when the exterior temp is blow a certain level its just a waste of energy to even try it. What I need to do is figure out some rules and relays such that:

whenever OutsideTemp is <40, 'heat calls' go to the gas furnace
whenever OutisdeTemp is >40, 'heat calls' go to the heat pump and 'Emergency heat calls' go to the furnace as well
(by calls, I mean whatever signals are sent from the thermostat control unit)

I have to admit i'm not terribly knowledgable on this, but what RCS told me is that they do not support this in their TR40 by default. I'm not aware of what the wiring & relays involved would be to accomplish my above goal. The heat pump installer is happy to work with me, but (understandbly) they are not going to spend many hours in this working on something that is not their issue. They are on the hook a bit though as the salesperson did look at my thermostat and said he would do research to confirm it would work in the system.

In looking at the AprilAire 8870, it appears it has a separate module to handle this scenario. Anyone using a 8870 with a heat pump?

 

[DavidL]

You must be using an Air to Air heat pump? Mine is Water to Air and the Water is a consistent temp year round so I don't have to worry about that case. I do monitor that temp with the new ML1WirePro MainLobby plugin. I monitor the exhaust water too, as that is the most critical setting on the system. Must be 32.5 F or it is inefficient (if higher) or will freeze up if lower.

A PC based or ELK / HAI based monitoring system the rules you need would be easy. Not sure about Thermo exclusive choices to do the same.

 

[Sendero]

You must be using an Air to Air heat pump? Mine is Water to Air and the Water is a consistent temp year round so I don't have to worry about that case. I do monitor that temp with the new ML1WirePro MainLobby plugin. I monitor the exhaust water too, as that is the most critical setting on the system. Must be 32.5 F or it is inefficient (if higher) or will freeze up if lower.

A PC based or ELK / HAI based monitoring system the rules you need would be easy. Not sure about Thermo exclusive choices to do the same.

I'm ok with it being dependent on my ELK. I'm just not sure how to wire it up. I'm guesing there are two control wires coming out of the thermostat and I'd basically use two relays controlled by the ELk. I'd want them to default to the gas furnace in case I lose power or the Elk stops working. But when the ELK is running and the temp is over whatever the cutoff is, it'd turn on those two relays and switch everything over to the heatpump. Again, I don't know much about how furnace/heat-pump wiring works, so just looking for advice here and will work with the installer to get it all wired safely and correctly.