New answers tagged fans
They make much quieter fans for this. There are many how-to guides out there on how to do entertainment center exhaust fan systems. You can google Entertainment center exhaust fan and see some pretty slick designs. There were a couple that were 'automated' If you are using 120v you could always get a Attic Fan Thermostat and connect it inline with the ...
You can buy a motor speed control, but you have to check the specs to see if it will work with your fan. I'm not knowledgeable enough in the area to tell you, other than to tell you it exists. A thermostat controlled relay is quite easy - you can buy a simple 120v relay and attach it to a standard home thermostat. Or buy something smaller made for it.
I don't think there is any restriction against an exhaust going downward. A slightly downward direction is standard in some installations, like when a soffit exhaust vent (common in extremely cold and snowy environments) is used with a fan box which sits above the ceiling joists.
There should be a switch on the thermostat that says "ON AUTO", make sure it's set to AUTO. If the switch is set to auto, but the fan continues to run. You may have a short between the R wire and the G wire, or a problem with the control board in the furnace.
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