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  1. #1

    Confused Carrier 58MVC with a 3-stage thermostat

    Hi guys,

    I'm new to the forum, first post, so hello! I'd bother carrier with this, but they're not open till Monday and I'd like some experienced perspectives on this one.

    I'm installing a carrier 58MVC 3-stage furnace and a Vision Pro IAQ. The IAQ is capable of 4h/2c stages.

    How does one use the thermostat to control the three furnace stages? The docs seem tell me that I'll need to connect it in one of the following ways:

    A - Use single heating stage from IAQ, let furnace modulate H, M, L (3 stages, but furnace controlled)
    B - Use two heating stages from IAQ, force furnace to L and M (ie just 2 stages, switches set on the board)
    C - Use two heating stages from IAQ, force furnace to M and H (ie just 2 stages, switches set on the board)

    The terminals on the furnace board are W/W1, and W2. No W3. The IAQ has W1, 2, 3, 4.

    As you can see, there seems to be no option to have the stat control the three stages, and I'd prefer that for this application since the IAQ is brainy and it's wired up to an extra remote indoor temp sensor, an outdoor temp sensor, humidifier, dehumidifier (via furnace) and HRV, and I imagine this as the central control of the whole operation so it seems to make most sense to have it decide on furnace stages etc.

    Am I missing something obvious here? Are there advantages/disadvantages to having the furnace or the stat control switching stages?

    Admittedly, I'm not a pro, my Dad is though (we're doing this together) and he's stumped too (he's not too handy on a computer, so here I am..) Please forgive me if this is an inappropriate post for this forum.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,331
    It does fall under no the DIY rule.

    Why not use the Infinity control for everything.
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  3. #3
    Join Date
    Jun 2006
    Location
    Hastings, MN
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    417
    You are cheating yourself by not having the Infinity control.
    Aint Notin Sweeter, Then A Brand New Heater!!!!!!!!!!

  4. #4
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,317
    The IAQ 4 stages of heat is 2 stages of HP compressor and 2 stages of gas heat. Wrong control! 3rd vote for using the Infinity control!

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Did you ever take notice, it list 3 stages of conventional heat.
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  6. #6
    Quote Originally Posted by mwjhvac View Post
    You are cheating yourself by not having the Infinity control.
    My dad (who loves carrier..) kept telling me the same thing. Maybe I should have listened!

    Thanks for the advice guys, sounds like I need to swap out the IAQ.

  7. #7
    Join Date
    Apr 2008
    Location
    Alberta Canada
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    2,246

    Let the furnace do staging

    Quote Originally Posted by jdelisle View Post
    My dad (who loves carrier..) kept telling me the same thing. Maybe I should have listened!

    Thanks for the advice guys, sounds like I need to swap out the IAQ.

    The other guys are right that Infinity control is a strong recommendation, but if you don't want to spend money, the IAQ is fine and the furnace will stage itself based on time and memory with PL4 card on processor.
    Do it right the first time.

  8. #8
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    34,317
    Quote Originally Posted by beenthere View Post
    Did you ever take notice, it list 3 stages of conventional heat.
    I stand corrected. But what 3 stage furnace is out there? Will the MVC let it run 3 stages or does that require the Infinity control? A-S/Trane's requires its matching special IAQ.

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,331
    Quote Originally Posted by BaldLoonie View Post
    I stand corrected. But what 3 stage furnace is out there? Will the MVC let it run 3 stages or does that require the Infinity control? A-S/Trane's requires its matching special IAQ.
    There are/use use to be some electric furnaces that can be wired for 3 stages.
    Around here, no ones been foolish enough to have one installed in many years though.
    Don't know if it will work on the MVC.

    Maybe Honeywell heard some manufacturers were coming out with 3 stage, and just made it able to do it.
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  10. #10
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,317
    That's true, most electric that have 25kw or more can do 3 stages.

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