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  1. #14
    Join Date
    Feb 2010
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    butler pa
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    1,073
    Quote Originally Posted by drewski11 View Post
    i'm surprised setting airflow to Max helped. seems like that would increase the static pressure and cause this error more often.
    i agree...id drop airflow to normal.
    id guess at max airflow you would be causing the stagedown w excess airflow/static pressure..

  2. #15
    I'll drop the airflow...perhaps it was just a coincidence that I was getting fewer of these readings with airflow set to MAX. So that I understand this, the less airflow allowed through the ducts, the less possibility of static pressure, and consequently an excess static pressure stagedown event? Dropping down to HIGH, or even MEDIUM if need be, would then resolve the excess static pressure stagedown issue?

  3. #16
    Join Date
    Feb 2010
    Location
    butler pa
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    1,073
    if you have a restrictive duct system..trying to get max airflow thru the system id think would cause your high static stage downs..see how dropping it does..

  4. #17
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,902
    You need to know what CFM is going through the cooling coil.
    A 5-Ton A/C with a TXV could go as low as 1700-CFM.

    The Return side & Supply side STATIC should be checked separate, may not have enough Supply-Air outlets & Return-Air ducting.
    Last edited by udarrell; 07-12-2010 at 09:40 PM. Reason: Removed & added content...

  5. #18
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,770
    It will take more then just a register or 2 to fix your duct system.
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  6. #19
    Quote Originally Posted by beenthere View Post
    It will take more then just a register or 2 to fix your duct system.
    What are you suggesting?

  7. #20
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,770
    You may need some major duct work alterations. Which will probably include some new trunk line, plus additional supplies and returns. And maybe even increasing the size of the existing ones.

    How big is your house?
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  8. #21
    The living area zone is about 1,200 sq feet and the bedroom zone is about 800 sq. feet.

    All new ductwork was installed in 3 of the 4 bedrooms, supplies and returns. New ductwork for the returns was installed in the living area zone, and some of the supplies runs are new as well.

    This only occurs when the unit runs in high stage, or only when there is a high demand for cooling (or heating). In low stage, no problems at all.

    Why doesn't the error always occur when the static pressure is greater than 1?

    Also, with the Infinity system being pretty smart, why does it allow more CFM into a duct than the duct can handle?

    Quote Originally Posted by beenthere View Post
    You may need some major duct work alterations. Which will probably include some new trunk line, plus additional supplies and returns. And maybe even increasing the size of the existing ones.

    How big is your house?

  9. #22
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,770
    Your trunk line has to be able to handle the extra air. Just increasing supply run outs doesn't help much.

    I don't think you get the error until it reaches 1.2" or more. But don't quote me on that.

    Its not that the control is trying to have the blower move more air then the duct can handle. It that you have smaller duct then the fan needs to move, that is the problem.

    What size was your old A/C?

    Was it a 4 ton?
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  10. #23
    Old A/C was also 5 ton. The house is probably about 2400 square feet with a basement that is about 2000 square feet. The family room has vaulted ceilings that are about 15 feet tall. The basement is its own zone, which does not kick on in the summer.

    If setting the airflow limits to medium or low resolved the issue and the house still cooled just fine, would that create any problems with the unit itself?

    There is almost no trunk system for the bedroom zone, and the runs are the round insulated flexible ducts. Do these round flexible ducts carry substantially less CFM than the rigid rectangular ducts?

    So I guess an extra dump run wouldn't help much? Although it would be a bit of a waste, if it would help I could add a dump to the garage.

  11. #24
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,770
    Shouldn't have a dump zone/duct with an Infinity zoning system.

    Try setting the air to low, and see if it stops the errors.

    Flex duct is often sized using a ductulator for sheet metal. So its often undersized.
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  12. #25
    I read in the manual that a dump zone is prohibited on the Infinity system. Why is that?

    In terms of my crawlspace, which I need to provide conditioned air to, would it be better off receiving air from each of the zones as opposed to getting fed by a dump off the main trunk?

  13. #26
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    Jan 2004
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    Lancaster PA
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    Probably best to just have 1 supply from one of the zones go to it. probably best to have it fed off of the smallest zone.
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