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Thread: Not getting 24V, but cooling and furnace fan work (but no heating)

  1. #1
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    Not getting 24V, but cooling and furnace fan work (but no heating)

    My setup is a gas furnace connected to an ecobee, plus I've got the Y terminals rigged through a couple relays to turn on my swamp cooler for cooling. Earlier this year I didn't have the cooling hooked up and the heating was working perfectly (the ecobee and furnace are both only about 3 months old). A few months ago I got the swamp cooler hooked up and after some trial and error, the cooling has been working perfectly all summer (with the small downside that the furnace fan turns on in cooling mode, but that's not a huge deal). However it's about to get cooler here so I tried to run the heat the other day to check that it was working, but it wouldn't turn on. I can get the furnace fan to turn on by sending a test signal from the thermostat for fan only, but if I call for heating, nothing turns on. I can see the 24V at the G wire when I call for fan only, but when I call for heat, either stage one or stage two, none of the relevant wires have voltage. Cooling works fine though. Is this just an issue with the Ecobee, like an internal fuse on the heating side or something?

    Last edited by bbrannon4; 10-04-2019 at 08:49 AM.

  2. #2
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    It was a silly mistake. There's a setting in the ecobee stating if both R terminals are connected or jsut one, and I only had one wire, but it set to two, so it was trying to pull power from Rh which had none.

  3. #3
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    Not so silly in my book, I had a similar experience with my heat pump o/b wire that switches the reversing valve. Apparently some units require activating the valve on cool and some require it switched on heat. These are programmed during the installer setup.

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