Originally Posted by markz528
Originally Posted by poorboy
The simple direct questions are: Can I run two hot water heat boilers off the same thermostat?
Thank you, Gene


As someone that has lived in the electrical industrial world for a very long time and play with HVAC, I would just use an interposing relay. The thermostat runs the relay coil and 2 independent relay contacts run to each boiler.

Now is that the best solution to run both boilers off the same thermoset, I don't know. But this will definitely allow you to run both boilers off the same thermostat with no issues.


I was under the impression that all the thermostat did was pull in a relay to start the circulation pump and then boiler would fire as needed. You don't think one thermostat has enough power to pull 2 relays in at the same time?
Where would I get an "interposing relay"? Pretty much all we have around here are big box stores.