I’m on the verge of purchasing a Nest thermostat for my upstairs zone - which is not heating, it is air conditioning only. The reason I’m doing this is to configure the Ecobee4, which runs the downstairs zone (both AC and heat), to prevent it from putting heat into the house if the upstairs AC is running.
But that is expensive.
And I do not wish to put power flow sensors on the 220 line that feeds the air handler.
Sooo… I’m thinking about some sort of airflow sensor. Looking for ideas.
My first thought is a very lightweight flap in an air duct, attached to a very lightweight spring. When the air begins to flow from the duct into the room, the flap gets pushed down by the air. This disconnects a circuit attached to a sensor, and that sensor then reports the event.
As long as the circuit is disconnected, the ecobee is forced into a mode where the heat start point is so low that the heat never turns on.
Of course, in the long term there will be battery costs - both for the sensor, and for my existing thermostat. The Nest running off the AC common, plus its learning capability, might result in it paying for itself soon enough… so I have to think about that.
In the meantime, anyone have thoughts on such an airflow sensor? Pitfalls? Better ideas? As one possible pitfall, I’m imagining it might create whistling noises in the duct…