Strong, gusty 45mph winds typical for Fall here have been messing with my induced draft blower vacuum signal to the pressure switch, especially the cyclonic nature of said winds this year.
Shuts the furnace down prematurely when alternating positive/negative pressure waves in the flue mess with the blower vacuum signal from gusts blasting across the furnace exhaust flue outlet above the roofline. Flue terminates approximately 22 feet above the ground, through the garage roof, along the split level exterior wall, through the adjacent eave of the attached main house terminating about 3 feet above the roofline. PVC 2.5 inch diameter.
Result: the pressure switch diaphram plunger taps the microswitch toggle just slightly enough to open the circuit making the furnace controller think the draft blower has failed--result, premature flame shutdown and begin another inefficient heating cycle. The flue top has a convex rain cap of course.
Draft blower is new last winter. Pressure switch vacuum tests prove ok for possible torn diaphram. Pressure microswitch continuity tests check ok at microswitch. I relocated the pressure switch closer to the draft blower with a much shorter hose a week ago when the wind was blowing thinking that would help with a stronger vacuum signal but particularly bad winds this weekend proved that futile.
Tonight it’s calm here for the first time in 4 days and the furnace is completing heating cycles normally. I’m now wondering what I can do to keep gusts from creating pressure waves down the flue or wind-capping the flue.
Does anybody know of a flue-cap product for just such a condition? Is there a flue cap made specifically for wind problems like this?
Edited by michla, 22 November 2012 - 11:55 PM.