Dry contact/Sensor basics help needed

I just got an Ecobee thermostat which I had to power with a transformer to C. The Ecobee doesn't have a way to tell if there is power to RH. I have installed Ecobee suite and it was recommended that I use a dry contact with a sensor to determine if there is power going to the thermostat from the RH/W wire.
Dry contact to monitor boiler power

I have tried a search (here and google) but the results assume ppl know how it all works. Is there a basics guide somewhere or can someone explain how to use a dry contact and sensor for my need? A schematic might be helpful.

Inside that Ecolink Door/Window Sensor is a pair of screw contacts. There's a tiny notch in the base to allow wires to be fed through and connected to. the internal screw contacts. The Sensor detects the resistance across the contacts and triggers it exactly the same as the magnet would. Open Closed. In this Boiler scenario you'd wire the 2 contacts of a relay to the 2 contacts inside the Door Sensor.

The coil side of the relay would wire across the 24v of the Boiler. When the boiler had power, the relay would and close its contacts, which would be detected by the Door Sensor and via ZWave, tell Hubitat. When the boiler didn't have power, the relay wouldn't either and its contacts would be open, the Door Sensor would detect and tell Hubitat.

The only hard part is finding a place to mount the 24v relay where the boiler heat doesn't damage it. :smiley:


You get 4 spares with this set :smiley:

1 Like

Not sure which ecobee you have. I have a ecobee 3 lite. The manual has the following statement:


And its not clear how you would determine if the RH has power using a dry contact.