Originally Posted by
realazy
So i've been trying to control the humidity better in the house after I had windows sweating during the cold snap last week and some water dripping afterwards from my ensuite speaker from frost melting. Hygrometer read around 36-37% during the cold snap (which I now know is too high) when it's -20°C outside). I lowered my humidistat setting so that the hygrometer now reads ~27%.
One suggestion was to use the ventilation switch a couple hours a day which runs the furnace fan as well as the bathroom exhaust fan upstairs. I have a basic Emerson programmable thermostat.
Poking around, I made some observations which seems like it's not logical. I have a fresh air intake damper that is normally open. This fresh air intake is tied to the cold air return on the furnace.
Its a simple damper that is 2 wires, 1 tied to the C (common) terminal and 1 tied to the G (fan) terminal at the furnace.
I observed 4 scenarios:
1. When I set the fan setting on the thermostat to AUTO and the furnace is OFF, the furnace fan is OFF, and the damper is not triggered (so it remains open).
2. When I set the fan setting on the thermostat to AUTO, and the furnace is on, the furnace fan is on, and I believe the thermostat does not send a signal on G therefore the damper is not triggered (so it remains open)
3. When I set the fan setting on the thermostat to ON, the fan continuously runs, and the thermostat must be sending a signal on G, therefore it triggers the damper ( so it closes).
4. When I use the ventilation switch below the thermostat on the wall, it turns on the furnace fan and the main bath exhaust fan, but this also sends a signal to G and triggers the damper (so it closes).
This logic doesn't make any sense to me and it seems like the builder installed the wrong type of damper? My logic thinks that I should have a normally closed damper on the fresh air intake so that it's closed normally, even when the furnace is running with the fan setting on AUTO. The damper should only open to fresh air when I manually set the fan to ON or use the ventilation switch.
Am I right or wrong?