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  1. #1
    Join Date
    May 2004
    Posts
    1,308
    An odd situation with a retrofit of two old downflow Lennox duracurve units with that nasty seven relay pack for twinning. Popped in a pair of Trane TDX furnaces.

    After a year of no probs... all of a sudden (and to no surprise) the boards have that dastardly issue of burn marks on the back of the boards at a pack of resistors nesltled snuggly on the center of the board.

    Normally, you'd get a series of intermettent 'false' problem codes, easily determined by the 'offending' part, is in-fact operating normally.

    We replaced both 'burned boards'... but get a intermittent fault code of nine flashes. Both ignitors have been replace. And the Thermostat was replaced with a digital H/W T5000 non-programmable. And for good measure, an isolating relay was installed to further alleviate T-stat probs.

    Is there anyone out there that is familiar with the Twinning of Trane Downflow furnaces and their potential anommolys?

    Situation:

    Application: Two 120,000 btu. Common return, common supply. Heating a small gymnasium. Heat load is correct.

    All installation requirements met. Common 120vac as per request for both furnaces. Solid 18/2 solid core stat wire. L1 - C = 123VAC, N1 - C = 1.3VAC, 3.2 MicroAmps flame signal on both furnaces. Gas pressures, and all conceivable tests were administered. But please feel free to overstate the obvious. It's a 100 miles out, and a pain in the arse to go to every other day.

    Any ideas?

    Thanks in advance.

    Ric
    Teach the apprentices right... and learn from their questions and ideas.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,316
    Burn marks on the board are typical of the Intell-ignition. Not related to twinning!

    Just follow the instructions, we've done a couple, I believe both have heat staged.

  3. #3
    Join Date
    May 2004
    Posts
    1,308
    Hey John... long time no hear.

    This set-up was installed and configured to the satisfaction of the installation guide.

    I discovered that the board issues were not due to twinning the furnaces. We have over sixty downflow furnaces in our area... every one of them are having probs with the CNT03076 boards. Once replace with the new board, CNT03798 ones... after about six months of ops, the discoloration is showing up again. We know it's not the board, but where it's mounted on the downflow... as it gets no cooling relief that the same boards do in the upflows that use the CNT03076 boards.

    The TDX120C960D3's are a single stage, nothing fancy furnace as you well know.

    As mentioned earlier, I keep getting locked out on 9 flash codes. Suggesting ignition failure or bad ground. It's a real head scratcher.

    It worked trouble free for a year, so air flow shouldn't come into play. I know I have approx. 4000 cfm to contend with, but the duct work is adequate for the load.

    I'm going to be calling the Trane Engineers on Monday, but just wanted to lay this out there, incase any other Choo Choo techs have run into this problem before.

    Cheers,

    Ric
    Teach the apprentices right... and learn from their questions and ideas.

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,316
    Those boards are a pain in every furnace, even the upflow with board in the cool return air. Haven't checked lately but our A-S supplier used to cover them regardless of age. Most common failure we found in the last year was 4 blinks, open limit despite all being jumped. Took a while to figure that one out the first time.

  5. #5
    Join Date
    May 2004
    Posts
    1,308
    Two thoughts then John...

    one: can you support the probs with these boards, as in how many failures have you found with 'false' fault codes, only to flip the board over to find that familiar burn mark on the back?

    Two: Any thoughts on this goofy 9 code prob I'm having with this twinned set of downflows?

    You have to have TWO answers... or else I'll think it's just a 13 year old responding... as we all know, if you ask six questions and only get the last one answered... You're 13.
    Teach the apprentices right... and learn from their questions and ideas.

  6. #6
    Join Date
    May 2004
    Posts
    1,308
    Oh... and here's a kick....

    I used to work for a HVAC/R wholesaler here in Western Canada. I was their HVAC/R tech support. Company is Sinclair Supply Ltd. (No, not the medical Sinclair Supplier in the U.S.) And about six years of venturing out on my own with troubleshooting stuff... I called my old compatriots for brand info on furnaces. I told them that there was this excellent web-site where this American fellow had the history on most furnace brands...

    They said... "you mean John Mills?"

    If I had a square arse... I'da ****e a brick!"

    Funny how the planet finds us all....
    Teach the apprentices right... and learn from their questions and ideas.

  7. #7
    Join Date
    Dec 2005
    Posts
    424
    isnt a nine fault code for ignitor problem on those furnaces? If furnace board thinks ignitor is open furnace wont work with sini ignitor. Checks resitance before furnace fires.

  8. #8
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,316
    Funny how that list shows up all over the net, some giving me credit, others not!

    What is 9 flash? I can't recall.

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