How can I safely install Nest thermostats to replace line-voltage units?

December 17, 2016 7:04 AM

My apartment has in-wall heaters in each room, with a separate line-voltage thermostat each. I'd like to replace those with Nest thermostats, but my understanding is that it requires special work.

What I'm looking for is not a DIY howto, but rather an assessment of whether this is possible at all, and how to explain what I want to a nest installer in such as way as to actually get a safe installation done.

posted by ChrisR to Home & Garden (7 answers total)

Not from what you've said. If there's a low voltage controller at the wall heater then you could, but I doubt that's the case. The line voltage therms are simply breaking the full power to each heater. That's the control and therefore there's nothing for the Nest's to become a part of.
posted by humboldt32 at 8:33 AM on December 17, 2016

Best answer: Sure it's possible. I haven't got a Nest, but I assume it's basically a sophisticated switch for low-voltage circuits, whereas the heaters are line-voltage. Following from that I think you'd need a contactor to switch each heater, a low-voltage wire from the Nest to the contactor, and a transformer to make the low voltage needed to trip the contactor.
posted by jon1270 at 8:58 AM on December 17, 2016

Best answer: This is certainly possible; you need a transformer and a relay for each circuit. It's a job for an experienced electrician.
posted by mr_roboto at 9:51 AM on December 17, 2016 [1 favorite]

If this is indeed an apartment you are renting, not a condo or something else you own, make sure you get written permission from your landlord before you try anything like this --- if they object, it could be grounds for an eviction or a lawsuit.
posted by easily confused at 1:25 PM on December 17, 2016

Response by poster: Yeah, it's probably worth clarifying, I own the place.
posted by ChrisR at 1:37 PM on December 17, 2016

I know that in the UK at least, the Nest thermostat comes with an add-on device called Heat Link which handles the high voltage switching.
posted by w0mbat at 10:26 PM on December 17, 2016

Best answer: I'll mention that the relay+transformer needed for controlling line voltage heaters from a 24V thermostat are pretty big. However you don't need to locate them at the thermostat; you can instead run extra low voltage cable from the thermostat to a control panel next to or near your electrical panel. This allows you to run a single transformer to serve all your zones. Little cube relays are cheap; an electrician (probably a Commercial/industrial guy) could rig something up for probably a few hundred dollars in material plus the cost to fish thermostat wires and time to wire the control panel.

There isn't anything special about the European Nest compared to the US version; it is just designed to work with European standards vs American and so could be grey market imported and installed in your residence. However if the European Nest doesn't carry a US listing it is technically illegal to install and theoretically could void your insurance if there was ever a fire.
posted by Mitheral at 7:32 PM on December 21, 2016