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  1. #1
    Join Date
    Jul 2016
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    Aaon make up air

    Iíve read this forum often but havenít posted anything until now. Had a call last year for replacing a roof top unit. I broke my foot so could not get there and sent one of my guys. He doesnít do much commercial but pulled some measurements and numbers. I also saw another companies proposal. Turns out it is an AAON make up air unit. I donít k ow anything about them so just got a price on an exact match. Holy cow they are expensive! The other company quoted a 5 ton Rheem roof top gas pack, not a makeup air unit. I told the owner I didnít think that was right. Then he got a quote from another Co. Who quoted a 7.5 ton Daikin roof top gas pack, again not a makeup air unit.

    The AAON unit is 100% makeup air. No return duct. Iíve walked away from the job but the owner owns a bunch of property that I service(residential). I donít want him to get screwed.

    Can you swap a 100% makeup air with a regular RTU gas pack?

    Thanks in advance.

  2. #2
    Join Date
    Jul 2018
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    Wisconsin
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    You need to exhaust what air you bring in. If they want to change to a MAU may be wise to get a engineer involved.

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  3. #3
    Join Date
    Jul 2016
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    Thread Starter
    They already have a makeup air unit. They got 2 quotes for replacing the makeup air unit with regular gas packs...

  4. #4
    Join Date
    Jul 2018
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    Wisconsin
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    What are they doing in the building?

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  5. #5
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    Jul 2016
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    Thread Starter
    Hotel

  6. #6
    Join Date
    Jul 2018
    Location
    Wisconsin
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    I would assume this is for a common areas such as a lobby or conference rooms. I would see no reason for 100% O.A. all the air brought into the building needs to go somewhere. There are fresh air requirments that need to be met tho. I'm sure you could use a RTU with DCV. I would check into a Modine Atherion, probably one of the most efficient RTUs with 100% OA capabilities. Heat recovery wheel, dehumidification and so on.....

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  7. #7
    Join Date
    Sep 2006
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    Obviously the nicest install is a “real” make up air unit, Aaon, etc. One of my customers has quite a few plain vanilla gas package units, 100% outside air. They are now 15 years old. They are in coastal Southern California, so, no ambient below 40F, not many hours above 90F. But they maintain space temperatures extremely close to set point. One system with very low airflow rusted out its heat exchanger. Two compressors have been replaced (18 others still pumping strong). Really don’t know how “regular” package units would fare in harsher climates.

  8. #8
    Join Date
    Jan 2004
    Location
    PA
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    Aaons are generally built site specific.

    There heat exchangers are made for operation at low outdoor temps.

    The one you were quoted may also include de humidification ability, and tie into a building automation system.

    It may or may not be a neutral air system/unit.


    I don't think a lot of checking was done to know what the unit being replaced does.
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    How many times must one fix something before it is fixed?

  9. #9
    Join Date
    Dec 2014
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    That unit is supplying make-up air for all the exhausts.
    I wouldn't be surprised if it's simply dumping air into the hallways , and maybe a couple open areas , and supplying tempering for those areas and dehum with reheat, and tempered make-up air for exhaust.



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  10. #10
    Join Date
    Jun 2014
    Location
    Dover, DE
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    Most of these hotel units, at least the ones I’ve worked on, are neutral air units supplying make up air for the exhausts in the building, as well as providing air exchange.
    This must be a very small hotel. As most of the ones I’ve seen, even on smaller buildings, are in excess of 15 tons.
    You need to determine what exactly the unit is there for.
    Modine is an excellent choice for a replacement with their Atherion line. They are expensive, and can be very complicated for someone that’s never worked on one, but they are very reliable, well built and efficient.
    ďI havenít failed. Iíve just found 10,000 ways that wonít work.Ē - Thomas Edison

    ďItís not whether you get knocked down, itís whether you get up.Ē - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

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  11. #11
    Join Date
    Dec 2014
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    Quote Originally Posted by rider77 View Post
    Most of these hotel units, at least the ones Iíve worked on, are neutral air units supplying make up air for the exhausts in the building, as well as providing air exchange.
    This must be a very small hotel. As most of the ones Iíve seen, even on smaller buildings, are in excess of 15 tons.
    You need to determine what exactly the unit is there for.
    Modine is an excellent choice for a replacement with their Atherion line. They are expensive, and can be very complicated for someone thatís never worked on one, but they are very reliable, well built and efficient.
    Any special tools needed to work on these Atherion units?


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  12. #12
    Join Date
    Jun 2014
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    Dover, DE
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    Not really, other then possibly a remote interface as they use Carel controllers that are mounted in the main electrical compartment. On 460V units the controller is not accessible without opening the disconnect switch. The trick is to run a small piece of ethernet cable down into the heating compartment and plug your interface into that. So if you have a problem with the unit, you can see what error it has without shutting off power.
    ďI havenít failed. Iíve just found 10,000 ways that wonít work.Ē - Thomas Edison

    ďItís not whether you get knocked down, itís whether you get up.Ē - Vince Lombardi

    "In this house we obey the laws of thermodynamics" - Homer Simpson

    Local 486

  13. Likes icy78 liked this post
  14. #13
    Join Date
    Aug 2002
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    Southold, NY
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    Quote Originally Posted by rider77 View Post
    Not really, other then possibly a remote interface as they use Carel controllers that are mounted in the main electrical compartment. On 460V units the controller is not accessible without opening the disconnect switch. The trick is to run a small piece of ethernet cable down into the heating compartment and plug your interface into that. So if you have a problem with the unit, you can see what error it has without shutting off power.
    I just love that Crap!

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