Why is there a potential of 24 volts between the R terminal and the other terminals on a thermostat sub base when the thermostat is not calling?
A) The common side of 24 volts is supplied through the coils of the devices that are not operating.
B) Thermostats are wired with both sides of 24 volts. One side is supplied to the R terminal and the other to all the remaining terminals.
C) The meter is reading voltage that is left in the thermostat wire from the previous operating cycle.
D) Thermostats have battery backup which can be read between R and the other terminals when the thermostat is not calling.
A
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