Add a smart thermostat to a boiler

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Hi Folks,

Bridgerman here. I invented the ThermGuard product and I now have another product that may be of interest to this group.

I have a boiler with multiple zones in my Montana home. I wanted a way to connect a smart thermostat like a Nest to my boiler system. The Nest had issues power stealing from the zone valves on my heating system. Since there are only two wires running to my mercury thermostat, I couldn't provide constant power to the Nest since it needs at least 3 wires to work (Common, Red, and White). I invented a small device that will connect to the zone valve and allow me to operate the Nest using only the two wires that are in the wall. It is called +wire.

I use the existing 24VAC transformer at the boiler and using only two wires in the thermostat wiring, I can provide a 24VAC signal, a common signal, to the thermostat (to operate and send/receive wifi signals) and the boiler gets a 24VAC heat signal from the thermostat.

There are other products on the market that will let you add a common wire for a smart thermostat but they require at least 3 wires in the thermostat wire bundle and most homes with boilers, only have two wires.

Bottom line: If you want to add a smart thermostat to a 2-wire appliance such as a boiler or even a millivolt freestanding stove there is now a product on the market that will work for you.

I'm thinking $50 for the product with maybe an extra $20 if you need the transformer.

Any thoughts?

There is definitely a need for this product, however, in an already expensive segment, I know I couldn’t afford 50-70 on top of the smart thermostat cost
Thanks for the feedback!

I used one of these to supply power to my nest where I only had 2 wire running from an old furnace. Not sure if it would work in your situation or not.
Amazon product
Hi Gbawol42,

Using this transformer required the transformer to be connected directly to the Nest...right? This means you have wires running up the wall, or perhaps locating the transformer behind the thermostat and drilling a hole through the wall to get the the Nest? The product I am talking about locates the transformer at the heating appliance and just using the two wires to carry the three signals necessary to operate the Nest as well as the heating appliance. I was shooting for a clean solution that uses the existing wiring. I have seen some video about using a transformer at the thermostat. The product also works for millivolt appliances as well such as a standing pilot gas fireplace or freestanding stove.

Thanks for the feedback!