Bryant Evolution two-stage furnace
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  1. #1
    Join Date
    Nov 2006
    Posts
    4
    My wife and I recently moved into our new house that has a Bryant Evolution two-stage furnace.

    Everything was working fine for the first month or so until we recently saw the System Malfunction error pop up on our control pad.

    We made a call to our HVAC installer who came out, checked the furnace and looked up the diagnostic code for the system malfunction. He relayed to me that the code indicated that the furnace's low-stage would not fire-up which he believed was due to wind blowing across/against the furnace flue and causing back pressure thereby preventing the low-stage from igniting. He suggested I put something around the exhaust pipe to block any strong winds from it. He also said that I could turn the system off and then reset power to the furnace to clear the warning.

    I've taken up his suggestion and I got a couple signs to block the wind from directly blowing against flue exhaust while giving it enough clearance so as not to block the intake or the exhaust (it's a concentric pipe). Everything was going good for about 2 weeks until it got very windy and I would keep getting the system malfunctions.

    Are there any kind of devices/contraptions to place the flue's exhaust to prevent this problem? Or could there be some other problem?

    Also, things have calmed down for the past couple of days and I still have the warning pop up on the control.

    I'm ready to call my HVAC installer but would like to have more knowledge about the matter.

    John

  2. #2
    Join Date
    Nov 2006
    Location
    Montana
    Posts
    134
    Hmmm...Strange indeed.

    At this very moment, the wind outside is howling and my 2 stage Evolution furnace is purring along.

    The technician can look up the history of faults to see how far back this problem goes.

    There might just be a problem with the low pressure diaphram switch. I doubt very highly that it is caused directly by the wind.

    ~Chris

  3. #3
    Join Date
    Apr 2004
    Posts
    7,680
    Can you tell us more about the vent? What size is the furnace (btuh's or model number), what size is the vent pipe, how long, how many elbows, increased or decreased at or near the furnace?

    IS there any archatecture or outdoor features that would funnel air into your vent? (carport, inside corner).

    Pictures would help.

    Oh.. is the drain installed into a plumbing stack or is it going to a floor drain or condensate pump?

  4. #4
    Join Date
    Jul 2002
    Location
    37725, work @ 37760
    Posts
    410
    Check the condensate trap and drain for pvc saw dust. Check the flue and intake for wasper nest or any other obsruction.

  5. #5
    Join Date
    Nov 2006
    Posts
    4
    The vent is about 2.5 inches in diameter. And it extends about 10 feet or so into the crawlspace and connects up to the furnace. There are 3 or 4 elbows along the pipe and the diameter is the same all the way to the furnace.

    The condensate drain is connected to a pump which is also fed by an Aprilaire 700 humidifier attached to the furnace and a dehumidifier that runs in the crawlspace.

    I believe the furnace is a 355 MAV, I'll have to look for the manual. I don't know the rated btuh, but the house is 1675 sqft and it's an energy star house.

    There's nothing that would funnel wind into the vent.

    I'll see if I can get some pictures to post tomorrow.

    Thanks,
    John


  6. #6
    Join Date
    Nov 2006
    Posts
    4
    Here are the pictures:

    Image 1: The vent to outside




    Image 2: Vent coming into house splits into Y for the inlet and exhaust




    Image 3: Vent pips leading from house wall to the furnace, point of view from furnace.




    Image 4: Inlet and exhaust pipes connecting to furnace




    Other info about the system. We have a 2-zone system with the 1st zone as the first floor and the 2nd zone as the second floor. I've noticed that the furnace has a system malfunction more often when the low-stage needs to kick on for the 2nd floor. The problem doesn't happen as often when the low-stage kicks on for the 1st floor.

    Thanks,
    John

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