I have a honeywell rth8580wf heating thermostat. I wonder what the output of the "white" terminal is (heating control). Is it only going from 0V to 24V or is it continuous depending on the room temperature?


closed as off-topic by laptop2d, pipe, uint128_t, Wesley Lee, Dmitry Grigoryev Mar 20 '17 at 10:11

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  • \$\begingroup\$ Try contacting Honeywell for the data sheet. \$\endgroup\$ – Leon Heller Mar 18 '17 at 15:15

It's a contact closure. When the thermostat wants heat, it closes a contact between the "Rb" and "W" terminals, which allows current to flow.

Here's a good reference for thermostat wiring in general.


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