adding outdoor thermostat to control boiler second stage

Dan_53

I have a two stage 300,000 btu boiler (NG) that has a high fire gas valve as well as the regular gas valve. The thermostat on our operating temp is set at a boiler inlet temp of about 170. The high fire valve also has an adjustable thermostat, which in the winter is set at about 145-150. So when the water temp at the boiler inlet is below 140-150, the high fire gas valve opens, and all 300K btu's are used. Currently, I have the high fire valve turned off. I only turn it on Dec-Feb. We live in northern CT. Is there any simple outdoor thermostat that I can wire into the high fire gas valve circuit that will allow it only to function when the outdoor temp is below 20 degrees? The boiler never has a problem with inlet water temps being too low. So I only need to run that high fire valve on the coldest days when all three hydroair zones are running as well as DHW. Thanks.

Unknown

Just a,,,

Normal HW spdt (single pole double throw)grey box t'stat with the proper range and a remote bulb will work. Sorry I don't have a number for you. I've used them myself for similar applications. Johnson makes a digital of the same configuration that works nicely as well. It needs power to operate though so the wiring is slightly more involved. I live in Hebron FYI.

Dan_53

Thanks...

does anyone know a model number of one that goes from say 0-50 and is compatible with 24v? I have found some, but they are compatible with 240v and 120 v. Would that mean that they are also compatible with 24v AC?