Smart thermostat

7 min read
Technically it is possible to use a smart thermostat such as the Nest with electric baseboard or wall heaters, but we no longer recommend it.

Update Oct. 24, 2016

After further research and discussion with Honeywell, we’re revising our stance on smart thermostats.

We no longer recommend that you attempt to install a smart thermostat to use with our products.

In the past few weeks we’ve been in discussions with Honeywell to get more solidified recommendations on specific relays and thermostats that can be made to work with line voltage heaters. We even began the process of bringing new parts and products into our system so we could sell the solution directly.

Somewhere along the way we learned that the relays Honeywell was recommending for this install don’t actually provide enough power to support smart and wifi thermostats for the long term. Even though we have performed successful testing with the Lyric and Nest thermostats in our engineering lab, we have concerns about the ongoing reliability and durability of this work around. We suspect running a smart thermostat with one of these relays as the power source may lead to the draining of the thermostat’s internal batteries.

We’re attempting to get more information from Honeywell and will post any updates as soon as we have concrete information.

We’re truly sorry for those of you who found this post in the past. Our goal with our blog is to support our customers' needs and to provide good, useful information to make them successful using our products in their home. We felt there were a growing number of you who were interested in having a smart thermostat or wifi control option with our heaters. In the past we felt this was a good solution. Unfortunately we don’t anymore.

We want to make sure you have the latest information.

Thank you for understanding.

We've updated the original post (below) to be more in line with our current stance on smart thermostats:

Looking to hook up a smart thermostat to your wall or electric baseboard heater? It's technically possible to make one work but you'll need to do a lot of extra work and research. Here's why: The Honeywell Lyric, Nest and other smart thermostats are designed to work with central home heating systems. Those are controlled by low voltage thermostats, which use 24 volts. Electric baseboard and fan heaters work with line-voltage thermostats, which can be either 120 or 240 volts. If you hooked up a low-voltage thermostat directly to one of our heaters it would fry the thermostat. Not the best way to spend $250. But that's where relays and transformers come in. The transformer converts the line voltage power into low voltage power to provide energy to the relay and the thermostat. The relay is then a bridge between the thermostat and the heater, allowing the low voltage thermostat to control the line voltage heater. (Keep in mind that you'll need one smart thermostat for each older thermostat you are replacing.) You'll want to make sure that you have a relay that's properly sized to provide power to your heater. You'll also need to get a transformer that's properly sized to power your relay and thermostat. (This is where you'll need to consult your thermostat, relay and transformer manufacturers.) You also need to check and make sure your transformer and relay works with your heater's voltage.

Installation outline

The specifics of the installation process will depend on what thermostat, relay, transformer and heater you have in your home, but here's how it will work in general:

  • The relay and transformer will need to be installed somewhere out of the way that is still accessible (like inside a closet, in a crawlspace or in an attic).
  • Line voltage wires will run from your circuit to the relay/transformer.
  • Line voltage wires will then go from the relay to the heater; all line voltage connections with the relay must be made inside a surface mounted metal junction box.
  • Low voltage wires will be connected to the relay/transformer (outside of the junction box with the line voltage connections) and will run through the wall to the thermostat, which will be installed on the wall. The relay turns the heater on or off using the signal from the thermostat.

Which smart thermostats will work?

We've tested this setup in our lab with the Honeywell Lyric and Nest but we can't verify this method will work with all low voltage thermostats or in all situations. We also suspect that this installation method may drain the thermostat's batteries, making it necessary to replace them on a pretty regular basis. If you have to have smart features or Wi-Fi connected thermostats, this method will potentially work for you but we hope to have a better solution in the near future.