Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Bosch IDS Heat Pump + hydronic backup heat Aquecoil

marios Member Posts: 1
I recently had a Bosch IDS 2.0 5-ton heat pump and air handler (BOVA-60HDN1-M20G) installed as part of my ducted HVAC system. Along with this, an Aquecoil hydronic coil was added for backup heating purposes. This way we have heat in case of a power loss (a somewhat common occurrence in my area of Connecticut) or if temperatures drop below 15F. We utilize an IBC propane boiler for our hot water needs and have incorporated an additional loop/pump specifically for the HVAC Aquecoil system.

However, the installer is struggling integrating this setup with a Honeywell T10+ thermostat. What's the proper thermostat wiring for this configuration? Specifically, should the hydronic coil be configured as AUX heat, similar to an electric strip heater, or does this setup require a dual-fuel system approach? I'm also looking for any wiring diagrams or guidance that could assist in this matter.

Ideally, I'd like to setup a system that automatically switches to backup heat when outdoor temperatures drop 20F or below. Given that propane is here quite a bit more costly than electricity—approximately 2 to 3 times more expensive per BTU—I aim to operate the system as economically as feasible. Any insights or advice on how to achieve this, without overly complicating the setup, would be greatly appreciated.



  • yellowdog
    yellowdog Member Posts: 157
    Bosch will provide you with all of the wiring diagrams that you need. Why are people afraid to call the manufacturer for help? The system was probably bought from FW Webb. Who is the installers salesman? They should also provide wiring diagrams.
    tim smith
  • Ironman
    Ironman Member Posts: 7,376
    edited February 20
    The T10 should bring on the hydronic when set to “Emergency Heat” by energizing a relay that signals the boiler and pump to come on.

    Do you have a generator that’s capable of powering the system during a power outage? You’ll still need power to run the hydronic system and the AHU during a power failure.

    This is the best solution:

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • leekshuster
    leekshuster Member Posts: 2
    While I realize what I'm about to share is a forced-air-based HVAC solution, it DOES share some common elements with the Bosch IDS system @marios mentions.

    In the fall of 2023, my daughter installed the same Bosch IDS 2.0 Heat pump (outdoor unit -- inverter/compressor) to replace her 22-year-old AC-only DX unit. At the same time, we decided to replace the (Indoor) Tempstar forced-air (ducted) furnace which was powered by natural gas.

    Indoors, a new forced-air furnace (Amana) has an "A-frame" coil that connects to the Bosch which can cover all central (space) Cooling or Heating. In our area (Utah) the local utility provides rebate incentives to encourage "Dual-Fuel" or hybrid solutions. (Check your local area.) Bosch overs a complete turn-key solution, but an Amana/Goodman (indoor) solution was chosen to save her some $$$.

    <<DHW is by a separate (stand-alone) direct-fired 53-gal Rheem.>>

    There is an optional resistance-heat "strip" backup option which we did not employ, as natural gas is our "AUX" backup fuel of choice. The "balance point" or cutover from electric (air-to-air heat pump) energy to "AUX" is currently set at 25 .F. At that point it is cheaper to burn nat gas (AUX), as the heat pump COP starts to decrease. (But the Bosch IDS can continue running down to our Design Temp of 10 .F (and below) but at reduced COP.)

    I was surprised to find how easy the system was to control. In our case, the contractor recommended an Ecobee Smart thermostat. (Which also had local utility rebates). It turns out there is quite a bit of hidden "intelligence" built into the Bosch IDS to control the variable speed inverter-compressor and allows for just about any thermostat to be specified. The Ecobee easily allows the homeowner to specify the AUX balance point. So far this heating season, the comfort levels are improved. The Ecobee-controlled transfer between "PRIMARY" and "AUX" is seemless and is undetectable unless you observe the IDS fan outside.

    An added benefit, the Bosch IDS heat pump is taking advantage of excess net-metered, roof-top solar PV power. It is too early to accurately report, but this winter's natural gas CH heating is way down, while electricity is up. Next summer's cooling (AC) season should show reduced electricity when solar PV peaks.

    The trend is for vendors to specify total turn-key solutions, but that makes "open" custom solutions harder to design, control and install. In my daughter's case, we were able to save $$$ by not going "all Bosch," including their thermostat.

    I'm not trying to specifically recommend brands or products here on the Wall. Understand, I am sorry I can not offer specific wiring advice to marios or the contractor, with a slightly different system. I'm just trying to share our positive experiences for others to draw from. I'm certain once homeowners, contractors, and suppliers get more experience with heat pumps -- We will share our experiences, and more affordable, reliable solutions will become available.