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Thermostats with dual heat system

Hello! We have just moved into a home that has a heat pump for forced hot air as well as gas furnace for hot water baseboards. The baseboard system has three zones, and Non-programmable wall thermostats on each floor (basement, first, second) that appears to operate each zone. There is an additional, programmable thermostat on first floor right next to other thermostat that controls the heat pump for heat/ac. So far, it seems we have to manually adjust the first floor baseboard thermostat whenever we need that heat to kick in if it’s too cold for heat pump. The aux heat seating on the heat pump doesn’t make the gas heat come on if the other thermostat is set at a lower temp. This is a challenge because we have the heat pump thermostat set to a schedule but the gas heat cannot be programmed to follow that schedule so we often wake up to or come home to a cold home. Is there anyway to integrate the two systems?


  • SuperTechSuperTech Member Posts: 1,336
    It seems to me that the house was meant to have the heat pump used in the spring and fall and the gas boiler in the winter when it's too cold for the heat pump to work effectively. It was probably originally just an A/C system at one point converted to a heat pump to save fuel in the spring and fall.
  • sascarolasascarola Member Posts: 5
    Ah okay. That makes sense! But our winter temps really seems to fluctuate especially in this first month. In the last 30 days average max was 48, average min was 31. Was very costly to use the gas heat, so on days when the heat pump will work, that seems to be much more cost effective. Are there any other options for having them work together?
  • sascarolasascarola Member Posts: 5
    Or, does it make sense to replace the non-programmable gas heat thermostat with a programmable one, so we have more control over the use of that heat during the day, or overnight?
  • Jolly BodgerJolly Bodger Member Posts: 209
    Get a new thermostat for the heat pump like a Honeywell VisionPro 8000 or IAQ installed with an out door air sensor. They can be programmed with an outdoor lockout temp for the heat pump and the stat will call for the gas. This will require a little knowledgeable wiring between the two systems. If you install two thermostats they will need to be carefully coordinated and will likely still be finicky, not taking full advantage of the HP.

    Using a single thermostat will allow you to set the change over temperature based on when the HP becomes less cost efficient than running the gas. I use a system like this to switch my hybrid system. I have a HP with a gas forced air furnace. Mine in not as elegant as a VP8000, it's old relay logic and mechanical thermostats.
  • sascarolasascarola Member Posts: 5
    @Jolly Bodger as it turns out, it looks like my hp thermostat actually IS the Honeywell VP 8000 and does have the outside temp sensor. But maybe it’s not wired to connect with the gas furnace. I have no idea
  • sascarolasascarola Member Posts: 5
    Or maybe it is just not programmed correctly. We think there is some kind of relay contraption in our basement and we have no idea what that is for.
    I would use the new Honeywell T10 Pro-Smart with Redilink Room Sensors. This unit does 3H/2C Heat Pump, it is dual fuel, geofencing, 7-day,5-2,5-1-1,1 or non-programmable, C-wire only and is energy star certified.
    Part number is THX321WFS2001W for the thermostat and C7189R2002-2 for the 2-pack of room sensors.
    You will never look at another thermostat again.
  • Jolly BodgerJolly Bodger Member Posts: 209
    @sascarola sounds like maybe it had been set up at one time. connecting the two heating systems on one control would need a relay. What you want it definitely doable. I suggest getting a HVAC Tech in there. If the two systems are not wired together correctly it can cause damage.
  • mikeg2015mikeg2015 Member Posts: 1,178
    edited February 1
    A vision pro 8000 or the T10 listed above is a great option or a white Rodgers IF95-1277 with the outdoor sensor. You will use seperate “R” for each system however.

    My preference is Honeywell because it has adjustable cycle rates. Boiler needs to be a CPH of 1 or 2. Heat pump a 3.
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