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Controls for hot water heat loop on steam boiler
I purchased a house which has a fairly new (2016 install) Independence Burnham natural gas steam boiler. I am in the process of renovating the basement, which is heated by a hot water loop running off of the boiler (the rest of the house is heated by steam and controlled by a Nest). The hot water loop is fed by a Taco circulator, which is connected to a simple line-voltage thermostat. When the temperature drops below the set point, the thermostat switch is closes, and the water circulates. The problem with the way it is installed is that the water circulates regardless of whether the boiler is on or not, and if the boiler is off (e.g., the main thermostat has not called for heat) the thermostat connected to the Taco has no way of turning the burner on to heat the water. So, in that configuration, it will circulate water all day long, but not heat a thing.
I would like to replace the line voltage thermostat with a typical low voltage thermostat. I believe I can do that fairly easily by adding a Honeywell switching relay to the Taco line. But, I would also like the thermostat to turn on the burner when the Taco is running. I attached a wiring diagram of my system. Any recommendations for how to wire that?
Thanks in advance!