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Discussion Starter · #1 · (Edited)
I have a Day and Night single stage high efficiency 80,000 btu furnace that is roughly six years old. I live at roughly 4500ft. I've had nothing but issues with my pressure switch since the house was built six years ago.

Every winter generally starting in December, it will trip constantly. Most often happens later in the evening or in the middle of the night. Switch trips three times and then locks our for several hours.

Basement is unfinished and the exhaust flue travels out the side of the house with a pitch in the exhaust. I'd say rough 1/4 inch per foot which is what it should be doing. I ve cleaned the flue with a dryer vent brush. Pet the instruction manual, with a 2 inch pipe, I should be fine up to 56ft. I have roughly 31 including elbows.

I've cleaned out the condensate trap several dozen times. Pressure switch has been replaced. There are two hoses on the pressure switch. One is like a molded foam and it runs to the inducer, the other runs to the condensate trap. Ive cleaned them numerous times. I've cleaned the ports on the switch with a paper clip. I've taken the inducer off and cleaned it out. The filter is brand new and I've even tried running the furnace with the doors off. The furnace is nearly spotless and clean. No rust, no standing or leaking water. A coil spotless as well.

I know it takes very little vacuum to close the switch and I've verified it by sucking gently on the hoses. I don't know what would cause the switch to open back up during operation. It ignites and runs for several minutes, sometimes has no issues. And then suddenly out of the blue it's acting up for days on end.

I'm using an ecobee smart thermostat and I've found a potential issue. The furnace by default should lock out when the pressure switch trips three times during a heating cycle. However, I'm noticing that the ecobee will call for heat, and show heating, when the blower is only running. It will try indefinitely to reach the thermostat set point which it never will.

With my old Honeywell thermostat, after three trips of the pressure switch, the furnace wouldn't restart until the lockout time had expired or until I flipped the breaker.

Not sure what the ecobee is doing.
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