Control 240 vac heating from low voltage thermostat (Nest etc.)

[keepersg]

Found this nifty relay for controlling 240 vac or 120 vac heaters from a low voltage smart thermostat. The devices have built in transformers providing 24 VAC for the thermostat. Available at Supplyhouse.com. I have no connection with the company. As an example, installation of a nest thermostat in our green house.

 

[JimS]

Those look nice and aren't as expensive as I expected. You can get a "fan control center" for less and does exactly the same thing but doesn't look as clean. "Relay in a box" also has some relays like this but you would need to add the transformer.

 

[LarrylLix]

I wouldn't put the stat over top of the heat producing relay coil and transformer. You would be surprised how many degrees it can throw the stat calibration off. People think they can compensate for the few degrees of difference but every time a breeze comes by (fans included) the accuracy changes.

 

[keepersg]

I wouldn't put the stat over top of the heat producing relay coil and transformer. You would be surprised how many degrees it can throw the stat calibration off. People think they can compensate for the few degrees of difference but every time a breeze comes by (fans included) the accuracy changes.

Yes, I wondered if that would cause issues. Mounted it that way for the picture and planned on moving it if that problem occurred (you saw the wire coil). However, the transformer only needs to provide minimal power (40 ma to the thermostat, 1.2 VA to the relay) to run the thermostat and relay. The devices stays cool in operation. I have other thermostats in the green house, one from Oregon Scientific that reads temperature and humidity and one from Ambient Weather. They all stay within +- 4 degrees F of each other. Two previous electromechanical thermostats (which failed after about 2 years each) were a disaster by comparison. Never could properly control the temperature with those.

 

[keepersg]

Those look nice and aren't as expensive as I expected. You can get a "fan control center" for less and does exactly the same thing but doesn't look as clean. "Relay in a box" also has some relays like this but you would need to add the transformer.

Yes, they're an improvement over my previous efforts of wiring a 24 VAC transformer and Picker 240 VAC/24 VAC relay together to do the same thing for some heaters in the house. Nice relay but a pain...