I am trying to understand the HVAC system in your house. Do you have two heat pumps and one oil fired furnace? Does each thermostat control a heat pump? Can either thermostat call for heat from the furnace?

How are the heat pumps integrated with the furnace?

Boiler or furnace?

Hi-

Sorry for not better explaining! Yes there are 2 heat pumps and one oil furnace. Each thermostat I believe controls a heat pump for each floor. There is an air handler for each floor (one in the basement and one in the attic.) Yes either thermostat can call for heat from the the furnace, I believe that is what the previous owner was doing manually.

The previous owner had a label (see attached image) on the top of each thermostat that directed him to put it into emergency mode manually for heat. In talking to him briefly he said emergency mode just calls for heat from the furnace vs. the heat pump. I have confirmed that since living here for a few days.

I hope that helps, please let me know if there are any other questions.

Chris

Do you have forced hot air heating from the furnace, or is it a boiler which heats up radiators or baseboards?

For the oil it's a furnace that heats up radiators. The heat pumps work through the forced hot air vents.

Your thermostat configuration is unique and complicated. It is beyond my expertise. I even think it would be a challenge for an HVAC tech.

Your 20+ year old heat pumps are living on borrowed time. My suggestion would be to not invest in new thermostats until you replace the equipment.

Depending on your electricity and oil costs, you may want to abandon the oil boiler. You could significantly reduce your energy costs with a pair of modern heat pumps.

Thanks, if you don't mind me asking, what makes this one unique and complicated? I've read a decent amount about hybrid systems, is this one a bit different?

I don't know how two thermostats can be wired to control one oil fired boiler. Do you have zone valves for your radiators? Have you followed the wiring back to the boiler?

The new thermostats need a common wire connection. This is not unique, but it is required. You may be able to use one of the wires you are no longer using and reconnected it at the air handler. If that is not possible you will need to pull an new wire if there are no other spares.

Let me see if I have this right:

You have two separate heat pump systems, one upstairs and one downstairs.n Both are forced air.

You have two separate thermostats controlling these systems.

You have a single oil-fired radiant heat system for the whole house. This system does not have its own thermostat. It is activated by either (or both) thermostat(s). The oil burner will activate whenever a thermostat calls for auxiliary heat or emergency.

Emergency heat will activate the oil system instead of the heat pump.

That new thermostat is pretty fancy. But it looks like most of the wires are the same, like R, O, B, Y, W and G. I whould have to look at the old Honeywell manual to see about X2 and T. I thought there was something on the Honeywell website that gives a chart for old and new wire designations.

You have to consult the Trane documentation of 20+ years ago to figure out how the heat pump connections (B, X2, and T) work in the old system. Not all manufacturers are consistent on how these operate.

The other interesting thing is that the heat pump works in either normal or emergency mode. The auxiliary mode is disabled. I don't follow how that works.

The is only one R connection on the old thermostat. This would imply to me that the same transformer is connected to the boiler and both heat pumps. This seems strange but I guess it is possible.

The other thing that needs to be done is to draw a wiring diagram. From that you can draw a diagram for the new thermostats. This can be done, but it is difficult to advise you without having all the wiring information.

Do you have an idea how much money it costs to heat and cool the house? The numbers may inspire you to start planning for replacement equipment sooner rather than later.