a house's two furnaces are not working. the pilot lights are on. The lady's brother said there is no voltage at the thermostat. where does the 24 v come from? a transformer ? where?
There are two step down transformers either 208 to 24V or 120V to 24V. The transformer is marked what voltage its rated for and also can be verified with a volt meter. You need to check inside the furnace for voltage by removing the furnace panel. Try this turn the fan to ON on the thermostat. If the blower comes on your getting signal. And have 24V. Now if you have batteries in the thermostats then either the contacts are dirty or the batteries are dead. So check that as well. Also, if for some off reason you took the furnace cover off and did not put it back on right. There is a door switch. If the switch is not making good contact the unit wont do anything. Lastly if you have an older furnace that uses a fan combination switch that may be bad. Try running the unit with the fan set to ON and then turn the heat on. If the heat comes on then the fan combination switch is at fault and your on barrowed time till the high limit device fails.
The transformer requires 120 volts then steps down to the 24 volts needed to power stat etc.Check by the furnaces and see if you can locate a light switch that is off and powers the transformers.Both should have a switch close by each unit.If any breakers are off in the panel then they would need to be turned on as well.
there will be no Reference to the 24 volt ground at the thermostat so checking for voltage there is a bad idea. some ware in the control circuit there is a transformer. the pilot light does not require 24 volt to remain on. look at the schematics on the inside of the access door to help you locate the 24 volt source. on an older furnace you do not need any voltage to light your pilot light. you could have a bad fuse
should be on the furnace. however the pilot light doesn't need the voltage to light. the solenoid does need the voltage to open.
