Have HVAC Questions? Ask an HVAC Expert for Answers
Good morning. I am Kevin.
There are a couple of things to check. Do you know if your thermostats are battery powered or are they powered by the unit?
If they are battery powered, then you need to check or change the batteries and see if this resolves the problem. If they are unit powered (24v from blower unit, or furnace) then you need to make sure the switch to that blower unit or furnace is turned on. Check also the breaker for that blower or furnace ( I believe you have already said you checked, but I would recheck) After that we would need to test for voltage at the thermostat.
if it is a heat pump, it is related to "fan coil". Fan coil is or should be on separate circuit on your circuit breaker panel. Most likely a 2 pole breaker, because it may include electric heat "backup". There may also be a service switch associated with the "fan coil" unit, it is located usually within 6 feet of the unit. may look like a light switch. there may also be breakers directly on the fan coil unit (1), that may be shut off. Turn off then back on. This will make sure that you reset it if it is tripped. If the breaker clicks back to a "center" position or off, it means you have a more serious problem.
Good morning. I just see the picture of the circuit breaker legend. Should be circuits 32-34, 16-18. I think I would also check 2-4 down the bottom left, this is labeled duct heaters. If you cannot find anything off, I would suspect a bad transformer or possible blown fuse on the inside of the "fan coil" unit. If you do open the panel on the fan coil unit, make sure you treat it as a "live circuit" unless you turn off breaker or service switch. Even though your thermostat does not have power, we can assume that the unit does and something else is dropping the power to the transformer.