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Feb 15, 2020
My wife and I purchased a Harman Accentra 52i Tc insert recently. We have a 2 story home in eastern PA with a heatpump zone for each floor. Both heat pumps are trane units with electric aux heat (pricey). My initial intentions were to wire the stove up to my thermostat to come on as the heat pump’s auxiliary heat during colder days of winter to cut down on my heating bill. I still also wanted to be able to use the stove for comfort purposes when I wanted and not just as my aux heat. I searched online and could not find anyone who has accomplished this successfully incorporating it in with a heat pump. From my digging I found that typically people splice a 24v relay into the stove’s thermostat wire and connect it to a smart thermostat. The problem with the new accentras is that they have the wireless battery powered temperature sensor and a back up hard wired temp probe. You would have to break both circuits and have them run independently for it to work how I intended.

First- I installed a Nest Pro thermostat and wired it per the wiring diagram I created. I jumpered W1/W2/W3 together at the Air Handler and ran the Thermostat wire to * (Emergency Heat) terminal. During set up of the nest I stated that I had a dual source electric heat pump with the second source being an electric radiator. I also programed the thermostat to switch to auxilary heat when the exterior temperature dropped below 38°. Note: If you need to power down the stove and still want heat for your home, you can select in the Nest to run on emergency heat which would be the heat pump coils.

Second- A new 18/2 thermostat wire was pulled from the nest (C & W2 AUX terminals) to a 24V Relay (7&8 terminals). The wired power supply was then installed into the back of the primary wireless sensor and the 12v Dc CCVT wire was fished down the wall to the 24v relay (3&4 Terminals). The 3v 1amp AC/DC adapter was then plugged into an outlet and connected to terminals 5&6 of the relay. When the nest calls for aux heat it will trigger the wipes on the relay to close the circuit energizing the primary temperature sensor.

Third- I spliced into one wire of the secondary temperature probe on the stove with 18/2 thermostat wire. This wire was then run to a second 24v relay and connected to terminals 3&5. A 24v wired transformer was then connected to terminals 7&8 and plugged into a smart plug. This sensor is primarily turned off and will throw a code on the screen of the stove saying the secondary temp probe is not connected. The only time I use the secondary temp probe is when the outside temperature is above 38° and we want to use the pellet stove for comfort reasons.

Attached are some photos of the work and a wiring diagram I drew up. Below are links to the items I used to complete the work. I hope this is able to help anyone with a similar idea.

Nest Pro Thermostat

AA Battery Power Supply

3v 1a AC/DC Adapter

12v DC CCVT Wire 2.1mm x 5.5mm

24v Relay

24v Transformer

Smart Plug

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