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  1. #1
    Join Date
    Oct 2012
    Location
    Sacramento,ca
    Posts
    196

    Carrier Furnace..any ideas?

    Have a 7 year old carrier 2-stage 95% furnace. I have cleaned all lines in this unit, checked ground, cleaned flame rod, getting the right flame sensing voltage all limits are working properly, gas pressure correct.

    The issue: It will throw a pressure switch code randomly and of course will never do it in front of me. I have been back to this house twice and found the machine locked out. Turned off power and starts up fine. I have started it dozens of times and every thing is normal on 1st stage and 2nd. Pressure switches close upon inducer spin up per spec and stay that way never drop out. This unit was installed with a single stage stat so it uses the board to determine when 2nd kicks in.

    My only idea is that when the inducer slows down for stage 1 after initial startup the switch is opening but it didn't do that in front of me. So, I jumpered the w1-w2 last time I was there and it is running fine now without any issues and no lockouts. Ideas?

  2. #2
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    2,101
    Vent pipe routing or termination, most likely the termination.

  3. #3
    Join Date
    Oct 2012
    Location
    Sacramento,ca
    Posts
    196
    Quote Originally Posted by kls-ccc View Post
    Vent pipe routing or termination, most likely the termination.
    Checked it perfectly clear only 8 feet straight up out the roof.

  4. #4
    Join Date
    Jan 2013
    Location
    Mistake by the lake
    Posts
    34
    I'm going with the pressure switch. Had a rheem 80%er do the same thing to me. Three visits later it finally showed itself.

  5. #5
    Join Date
    Jan 2011
    Location
    Ottawa, Canada
    Posts
    386
    Check for slope of furnace. Backed up water can slosh and trip the p/s randomly. Ive seen it a couple of times this year.

    Sent from my GSIII on Tapatalk

  6. #6
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,189
    I don't see where you measured the actual pressures being sensed by the switches. I recommend a quarter inch tee. Then you can watch it run.
    Perhaps you should have read the instructions before calling.

  7. #7
    Join Date
    Mar 2004
    Location
    Illinois
    Posts
    6,959
    Micro switch on pressure switch tends to be an issue on these. Jiggle the wire(s) on the terminal and see if it drops in/out, if so bad switch.

    Otherwise my crystal ball says circuit board.

  8. #8
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,189
    Quote Originally Posted by Senior Tech View Post
    Micro switch on pressure switch tends to be an issue on these. Jiggle the wire(s) on the terminal and see if it drops in/out, if so bad switch.

    Otherwise my crystal ball says circuit board.
    Part changer.
    Perhaps you should have read the instructions before calling.

  9. #9
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    2,101
    Quote Originally Posted by Barrettservices View Post
    Checked it perfectly clear only 8 feet straight up out the roof.
    The question is "Is there anything going on that wind will cause tripping?" I have seen some where they terminate with 90s or U bends out the roof. Most nuisance trips I see are either drain or termination related.

  10. #10
    Join Date
    Mar 2004
    Location
    Illinois
    Posts
    6,959
    Quote Originally Posted by jrbenny View Post
    Part changer.
    No... I direct the parts changers

  11. #11
    Join Date
    Oct 2012
    Location
    Sacramento,ca
    Posts
    196
    Quote Originally Posted by jrbenny View Post
    I don't see where you measured the actual pressures being sensed by the switches. I recommend a quarter inch tee. Then you can watch it run.
    I removed the hose and measured at startup before it cutout and it was within the switches spec. Besides you can see the plungers on the switches where it contacts to microswitch and they are always pulled in and away from the microswitch when running. The only odd thing I noticed was when I arrived once the code said 2nd stage pressure switch stuck closed but i checked that first and it was open.

    As for water this is an upflow perfectly level and i don't hear any sloshing and the water is draining great. Watched it run for 20 mins straight without water issues.

    As for the exhaust on the roof it is a concentric that is clear of debris so wind shouldn't be an issue and it has run for 7 years or so without wind issues.

    so it sounds like if it does it again the consensus is the pressure switches.

  12. #12
    Join Date
    Mar 2004
    Location
    SE Michigan
    Posts
    17,940
    Rarely have I seen a pressure switch go bad, especially on a 7 year old furnace.
    Behind the ostensible government sits enthroned an invisible government owing no allegiance and acknowledging no responsibility to the people.

    Theodore Roosevelt

  13. #13
    Join Date
    Aug 2012
    Location
    MN
    Posts
    80
    Water in pressure switches. Replace switches and remove and flush trap.

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