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  1. #1
    Join Date
    Oct 2017
    Location
    SW Michigan
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    FYI: Cozy Wall Heater Fan Switch

    We have a customer with a recently installed Cozy DVCF553, natural gas. Customer notifies us that it seems to be getting very hot, but the fan switches on and off every 20-30 seconds with a 5-10 second off period. The unit is in a garage shop, which is kept at 60F.

    After one day in operation, the heat exchanger has dark stress marks like it is getting too hot. We check operation, talk to manufacturer who tells us since the room temp is cooler, the fan will cycle shorter. Duh. Original fan switch was a 110-15F, 15 degree differential.

    Our solution: replace fan switch with a larger differential. 110-30F. Works like a charm.

    Thoughts?

  2. #2
    Join Date
    Mar 2013
    Location
    Billington Heights, NY
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    I would bet that in short order you will be replacing that unit. It'll condensate inside and the HE will puke. Heaters are not designed to be run in low ambient temperatures.
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"

    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

    Jtrammel - "I’m going to sell hvac systems derp derp derp"
    BBeerme - "every time he opens his mouth, he reminds me of a cow without the fart bag."

  3. #3
    Join Date
    Oct 2017
    Location
    SW Michigan
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    Thread Starter
    Thanks Marc, I understand your point. Is this an industry recommendation for direct vent heaters? I was always under the impression from condensing and non-condensing forced air residential furnaces to keep ambient temps at 60F or higher, so I thought we were in the clear. I should have measured temp rise, but it sure runs hot like most wall furnaces.

    If there is documentation that condensation will form on this HE running at 60F ambient, I would like to recommend to our customer to run it higher and any future customers, I would go for a different heating solution.

    How does Reznor get away with running low ambient temps 40F and cooler? (I know, wall heater vs. unit heater)
    I cannot yet post a link.. but if you search for 'Reznor cq3' there is a PDF for a relay kit that Reznor sells that can enable some of their units to run in sub-40F ambient temps.

  4. #4
    Join Date
    Mar 2013
    Location
    Billington Heights, NY
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    Quote Originally Posted by ron_t View Post
    Thanks Marc, I understand your point. Is this an industry recommendation for direct vent heaters? I was always under the impression from condensing and non-condensing forced air residential furnaces to keep ambient temps at 60F or higher, so I thought we were in the clear. I should have measured temp rise, but it sure runs hot like most wall furnaces.

    If there is documentation that condensation will form on this HE running at 60F ambient, I would like to recommend to our customer to run it higher and any future customers, I would go for a different heating solution.

    How does Reznor get away with running low ambient temps 40F and cooler? (I know, wall heater vs. unit heater)
    I cannot yet post a link.. but if you search for 'Reznor cq3' there is a PDF for a relay kit that Reznor sells that can enable some of their units to run in sub-40F ambient temps.

    It's pretty much an industry standard. Running cool/cold air across a primary exchanger when the heater is maintaining a low ambient is likely to cause condensation and rot-out.

    The cq3 kit is designed to keep the heat exchange temperature UP, as if it was operating in a "normal" temperature. The regular fan switch will then operate normally.
    Experience - knowing when to get the hell out of the way and plug your ears. "Don't be a sissy. Turn it on!"

    Poodle Head Mikey - "the world is well populated with the unknowing and the uncaring and the stupid."

    Jtrammel - "I’m going to sell hvac systems derp derp derp"
    BBeerme - "every time he opens his mouth, he reminds me of a cow without the fart bag."

  5. #5
    Join Date
    May 2006
    Posts
    3,376
    Post Likes
    most of the units i have fixed the blower turns on at about 110F and turns off around 80F your unit sounds like my furnace when the blower switch a themodisk switch was getting weak and not snapping on all the way.
    Put a new one in from empire and it works like a new unit

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