York Affinity 9.C LP furnace intermittantly doesn't work
My house is about 6 years old I bought it 1.5 years ago. My HVAC system is a York Affinity 8T series heat pump (model # YZE06011B), a York Affinity 9.C gas furnace (burning LP, model # PC920N120DH11A). It has 3 zones, controlled by a Honeywell TrueZone (model HZ432). Each zone thermostat is a Honeywell model # TH8321U. The original installer is out of business and no one in my area services York HVAC stuff. My problem is that the gas furnace intermittently does not kick on when it’s supposed to (colder than 30 degrees or so). I’ve had two different service outfits come in. One replaced the pressure switches, rerouted the pressure switch hoses, and then threw up his hands and said “it’s the nature of the beast!” and quoted me a new furnace. The other guy changed the control board to a Honeywell TrueZone model # (the original control board had a blown resistor). On my own, I’ve cleaned out the condensation trap, added water to the trap, blown out the drain hoses, changed the filter, and drilled a drain hole in the horizontal vent pipe since it looks like it’s sloped to the left (let out a bunch of water!). I thought this was my breakthrough, but on the last cold morning the furnace didn’t come on. Both guys pointed out that a prime suspect is my vent pipe having too many elbows. It’s about 18’ of 3” PVC pipe from furnace to roof with 5 elbows (the York installation manual allows for 35’ with 5 elbows). I’ve also read up on the TrueZone and the thermostats, gone through all the checkouts, and all the wiring seems to be in order. I’ve already spent $1000 on this and am not convinced that these service guys can help further. Link to some pictures: https://picasaweb.google.com/reallyt...CPvwh5H0mNPoMg I’m not a service guy but am an engineer and can diagnose basic stuff. If anyone has any ideas, I’m all ears. Go onto the york website and hit find a dealer. A good dealer should be able to work with york (or maybe a rep of york) to resolve the issue. ------------------------------ Other ideas: When the furnace fails, does it give an error code? (flashing led?) You said it fails when it's below 30F. Does it ever fail in mild weather? Is the furnace in a cold garage? High efficiency furnaces shouldn't be installed in cold spaces - at least without taking precautions to prevent the condensate lines and trap from freezing. Has the furnace had this problem since day one? You can rule out the zone controller by disconnecting the wire connected to W and jumpering R + W at the board. ------------------------ and drilled a drain hole in the horizontal vent pipe since it looks like it’s sloped to the left (let out a bunch of water!) That might be part of the problem. Horizontal vent runs must slope towards the furnace so condensation doesn't accumulate. Any water in the exhaust pipe is supposed to drain back into the furnace. ----------------------- Ducts look kind of small for a 120 000 btu furnace, but i could be wrong. There's no dealer within 50 miles from me. 1) the board flashes 3 red's. 2) It works just fine in mild weather. 3) The garage also contains 2 gas fired water heaters so if the garage doors stay shut, the garage stays above freezing. 4) I'd say this problem has happened intermittently for the last two years. I bump into the previous owner once in a while, so I'll ask him. I installed that drain line just recently and haven't tried it long enough to see if it makes a difference. I think I might try re-doing the vent myself by going straight up, using 45 degree elbows and eliminating any horizontal runs. Thanks for your response. update on this problem: The three flashing reds indicated a stuck pressure switch. I tested it and sure enough, the new pressure switch was stuck open. I replaced it and all is well for now.
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