How does a 2 wire 24 volt ac electronic thermostat work to control a gas fired furnace ?
Have moved into a house where previous owner replaced simple mechanical type thermostat (with mercury bulb) with an electronic unit. Mechanical type obviously just closes a contact to complete the gas valve circuit and so get 24V across gas valve coil. you are correct, the electronic tstat needs to be powered, some cheaper thermostats will operate on 2 AA batteries(junk in my opinion) or the other will actually be powered from the 24 volts on the unit transformer, verify that its wired correctly, is
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