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  1. #14
    Join Date
    Nov 2001
    Posts
    181
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    Quote Originally Posted by BillDX View Post
    Why are they almost always mounted next to the blower, which is likely to have micro vibrations, and in the return air stream?

    An exposed circuit board, especially modern ones with low voltage components and very tight traces, should be enclosed in air tight enclosure. Those boards have nothing on them that generates heat. Why mount them where they are exposed to an air stream and vibration?
    Enclosures cost money. 99.9% of customers will not pay extra for an enclosure. Hence, no enclosure. I worked for an HVAC manufacturer for years. This is the mindset.

  2. #15
    Join Date
    Jan 2014
    Posts
    61
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    Thread Starter
    How often is corrosion of contacts a problem?

    The terminals that I see that are soldered on the control boards are not rated for outside use. But that is certainly the case when it comes to condensing units.

  3. #16
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    44,140
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    One reason for the board in the blower area...

    Keeps it DRY!

    Constant air going across it... dries out humidity.

    If the system is installed correctly (which requires hiring an HVAC co based on quality, not lowest bid)...

    There will not be many board killing issues.
    GA-HVAC-Tech

    Your comfort, Your way, Everyday!

    GA's basic rules of home heating and AC upgrades:
    *Installation is more important than the brand of equipment
    *The duct system keeps the house comfortable; the equipment only heats and cools (and dehumidifies)
    *Cheap is not good, good is not cheap; however expensive is not a guarantee of quality!
    Choose your contractor wisely!

  4. #17
    Join Date
    Mar 2018
    Location
    Chico, Ca #StateofJefferson
    Posts
    1,851
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    All boards are built by price. A cheap, no frills furnace is going to have the cheapest board the manufacturer thinks will get them out of warranty- 10 years. The boards in higher end furnaces go bad much less often maybe on the order of 15-20 years before failure. Board life expectancy is much more dependent , I think, on if the furnace is properly sized (less cycling), where you live (Los Angeles vs St. Paul). I couldnt find it but I remember seeing a map of the US broken into geographic regions and how often the heat would cycle, in the Sacramento valley where I'm at 10k-15k cycles per winter could be expected and some place like St. Paul might be 30k-35k. Furnaces with PSC blower motors will often have a failure in the blower relays as these are line voltage and will often have twice the relays rated amperage go thru them on motor start. This is not an issue with ECM motors as the blower motor is always energized and the board only sends low voltage commands signals

  5. #18
    Join Date
    Dec 2002
    Location
    Houston,Texas
    Posts
    20,025
    Post Likes
    Come now! If they didn't install it in the blower area, it would not collect dust and overheat, and they wouldn't be able to sell you more boards. I have seen boards in the blower area where it had 1/8" of dust/dirt on it.
    __________________________________________________ _______________________
    “Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law

    "When the teachers become unteachable we're all in trouble"

    "It's what you learn after you know it all that counts." ~ John Wooden



  6. #19
    Join Date
    Aug 2009
    Location
    Beatrice, NE
    Posts
    10,719
    Post Likes
    I am a Trane dealer and I have only seen 2 boards (1 under warranty) fail in 2019 so far but we still have a ways to go till the end of the year so that number could go up.

    I don't have a problem with the board in the return except the older I get the harder they seem to be to get to, and then with bi-focals harder to see.

  7. #20
    Join Date
    Jun 2001
    Location
    San Diego, CA
    Posts
    1,191
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    and dry . . ie not in the supply air stream

  8. #21
    Join Date
    Dec 2002
    Location
    in a house, Appomattox, Va.
    Posts
    4,772
    Post Likes
    I've seen a few from coleman that had enclosures, but the units don't like the higher utility voltage in our area, so we're not likely to be installing many, and they're the high end version.

    York rtus were bad about eating boards and other components if you had an airleak into the board area. was in the return side and inside the insulation, so cold, and any air leak would condense like crazy on them.

    Also, downflow westinghouse air handlers, manuf will not honor warranty on those baords, even though every one I've seen bad was water leaking on them. manu has moved the board, which is what I do when replacing one.
    Col 3:23


    questions asked, answers received, ignorance abated

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