Electrical – Add A Sonoff To Home Thermostat

electrical

I would like my A/C to self turn on at 8pm, that is before I get home and have the ability to cut off power automatically. I have Sonoff basic devices doing this with my lawn lights, pool, etc. I have a 1 Channel Inching /Self-Locking WiFi Wireless Switch 5V 12V that's been sitting here unused:

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I connected it to 1 zone of my sprinkler system and it worked as expected – when the sprinkler controller turned on that zone I could turn on/off the Sonoff WIFI switch which then turned on/off that zone but for so long, then off. I thought it's summer, turn the HVAC selector to AC, find the power line, cut it, insert them in this low voltage Sonoff, and I can turn on/off AC on my phone or just use a set timer. The thermostat is a Honeywell RTH110B here is installation manual. Sonoff device is powered by cellphone charger or 12vc dc connectors.

Best Answer

This is an old question, but there are several solutions here that may help others who stumble upon it.

The easiest and most consumer-friendly way to do this is with a "smart" thermostat, these are designed to be controlled remotely and also can be activated when you're home/away, at a set time of day, minimum/maximum temperature, or when you reach a certain distance from your house (tracked by GPS).

The Sonoff you mentioned is capable of doing this as well, in a tinker/hacker way. I would actually recommend you use a 2-channel Sonoff so one channel can control heating and one channel control cooling. As you're configuring the Sonoff remember that "inching" means "momentary connection" and "locking" means "closed circuit" like a normal switch. I believe thermostats "lock" until the desired temperature is reached. Sonoffs contain relays with several hundred volts and several amps of capacity.

As @dandavis commented previously, I would wire these in parallel with your thermostat wiring so that your thermostat still controls your system also. The answers about what to connect with what should be in your thermostat manual, I haven't read it. If you're more of a "do-er" than a reader, you can use a voltmeter to check the thermostat's continuity during operation and figure out where to bridge your Sonoff that way.