Any Carrier Dealers ..need some info
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  1. #1
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Ive ordered 2 carrier rooftop 7.5 ton package gas units to be installed on top of a hotel..model 48TMD008---5. These units will have a horizontal supply duct. There is no existing return duct and is open 100 percent to outside ambient. The units im replacing are carrier 7.5 ton units and they are ducted this way and have worked fine for many years. My question is this. I was going thru my carrier book the salesgirl gave me and noticed that it says that when this unit is ducted horizontal that the accessory barometric relief or power exhaust MUST be installed on the return ductwork. I was not told of this before I ordered the unit and salespeople were fully aware of the setup i have. Its gonna piss me off if i have to send for this fan accessory as i did not quote that in part of my bid price. How important is it that this accessory be installed in this particular application. My thinking is that it will help with head pressure. Any info you can give me will be greatly appreciated. The existing units appear to have been altered in slowing the fans down by altering the pulleys and I will be doing the same with these units.

  2. #2
    Join Date
    May 2004
    Posts
    1,462
    Barometric relief or power exhaust have nothing to do with head pressure control. They are to relieve over pressurization of the building when you are pulling in outside air. It sounds like you are using all outside air so the building will be positive pressured unless you have some way of relieving it. Since you do not have any return duct, the relief must be elsewhere on the building.
    If all else fails....Try reading the directions!

    Tell it like it is and let the chips fall where they may.

    Any views or opinions stated here are strictly my own.


  3. #3
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Thanx plain spoken..pardon my ignorance on the matter but i grew concerned. I had to ask to be sure as i do not like doing half arse type work.

  4. #4
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Actually I should have looked more closely at the description of the accessory because it plainly states exactly what you just told me...lol.

  5. #5
    Unless I am missing something you are gonna rust out them heat exchangers by using 100% outside air.
    Hey cockroach, don't bug me!

    www.AskTheDiceman.com

    www.TheColdConspiracy.com

    www.Pennwood-HVAC.Com

    Bring Em Home....

  6. #6
    Join Date
    May 2004
    Posts
    1,462
    I had already thought of the same thing, but marketing in their zeal to sell has signed off on 100% OS air. Not sure if that would hold true in your area, but in the Carolinas it is done.
    If all else fails....Try reading the directions!

    Tell it like it is and let the chips fall where they may.

    Any views or opinions stated here are strictly my own.


  7. #7
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    Yes that maybe true however in this particular instance not much i can do about it. There is no possiblility of adding return ductwork to these units...5 story hotels and the units cool hallways in the lower floors and elevators. I have examined the hx in the two units im replacing and to be honest they look fairly normal for units that are over 20 years old. However the new hx they make may not fair as well. Regardless the guys at carrier know full well what the situation is and all they wanted was the check. Told me it would void no warranties ect..a few other companies in the area have told me theyve run into similar situations. Kinda makes you wonder who the hell designed the hvac system for these hotels and how in the hell did it ever pass inspections and codes.

  8. #8
    Join Date
    Nov 2003
    Location
    South Carolina
    Posts
    1,167
    As a note on the hx...I probably could have gotten away with just putting a straight air unit up on this hotel as the furnaces rarely if ever ignite during the winter...usually almost warm enough in these hallways that it is closer to calling for cooling than heating in winter.

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