Attic Fan Bypass Switch
02:00 PM: I installed a bypass switch on the attic fan, because the fan wouldn‘t run enough when it got very cold, though these times are precisely when it should run the most, to keep excess humidity and moisture out of the attic.
Before the switch, temperatures below 30 degrees tripped the thermostat OFF, even when set to the coldest activation setting possible. Therefore, the fan would not operate when temperatures plummeted too low. So, as frigid as it’s been the past few days, we’ve seen little fan operation. Correspondingly, there’s also been an increased buildup of condensation in the attic, intensified by our vent-less gas heaters in the basement.
To better combat this dampness, I wired the bypass switch in parallel with the thermostat. Now, moving the switch into the ON position bypasses the thermostat. Thus, the fan operates, even when the thermostat is OFF. That is: when in bypass mode, the fan runs, regardless of the setting of the thermostat. Eventually, I plan on installing a humidistat, which would activate the fan when the humidity in the attic reaches an appropriate level. But, until I can bring myself to spend the $50 that a good humidistat costs, the bypass switch should make a good stop-gap measure. True, with the humidistat, the fan might not run as much as it will when in bypass mode. But it’s a small fan and consumes little electricity. So I doubt that adding the humidistat would pay for itself in electricity savings any time soon.