alt Hacker NewsAnnoyingly, both Ecobee and (at least historically) Nest make controlling the fan independent of the heating and cooling hard. You have to enable either heating or cooling before being allowed to enable the fan. And you can't specify how long you want to run it for, but have to select one of a few options.
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flanz_10 • yesterday at 6:47 PM
i have an ecobee and it was pretty simple to hit fan on even when system is off. this may be a limitation of your hvac system being exposed awkwardly through to ecobee. some systems have a "fan only" wire, which mine does. but my guest house is a much older system, and it is like yours.
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Could just bypass with esp32 and relay. I think you just need to close a 24v AC switch/relay unless you have a newer/more expensive communicating system (although then I don't think you'd have an Ecobee)