HVAC Logic Question

[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?

[ThePenIsMightier]

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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?

I know a little about this but no expert.
#4 sounds very wrong. If you're attempting to manually circulate and exhaust, it should definitely have that damper open so you're exhausting more effectively. This will also allow your air inside to become less humid. It's not technically dehumidifying it but it's sending the moist air out and letting it get replaced by air from outside that's most likely less humid. HRV units help with this but it sounds like you don't have one.
I disagree that you think it should be closed permanently while on auto. My HRV activates and brings in outside air on its own while my furnace is in auto. Sometimes during a heating cycle and sometimes not. I believe it's designed to target a certain # of Air Changes per Hour (ACH) and should still open during auto.

[realazy]

I spent a couple hours with a friend tonight thinking about the setup, my setup just seems to be wired wrong without a relay.

What the normally open damper (power close) needs is constant power to keep it closed and is interrupted when the furnace turns on OR the vent switch on to open. When just the fan is turned on through the thermostat when the furnace is off, the damper should remain closed to allow you to circulate the inside heat

I’m calling the builder tomorrow to complain. This is blantantly wrong and is messing with how the whole hvac system works.

[ThePenIsMightier]

Good luck.
Keep in mind that you can just leave a few windows and a door open for a half hour on a cold day and a ton of moist air will leave your house. Mine explodes out like a sauna when the door is opened on a super cold day.