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  1. #1
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978

    No visible return grille?

    I was at a local store today and noticed the RTU's had a supply trunk with normal supply grilles, but the separate return trunk came down a few feet and then 90'd into a trunk of about ten feet with no visible grilles; the only way these returns would have a grille would be on the ceiling facing side. Has anyone ever seen a return with the only grilles it has is on the ceiling facing side? Is it possible somebody forgot to put grilles in the returns and the RTU's are getting their only return air from the economizers?
    An answer without a question is meaningless.
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  2. #2
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    If it was above a grid then most likely a common plenum with returns in the light fixtures.

    Very hard to spot.

  3. #3
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    No it's not like that. This is just a situation where you can look straight up and see the underside of the flat roof. You can see where the supply & return trunks some straight through the corrugated metal of the ceiling. The supply trunk comes down 2 or 3 feet and 90''s over accross the ceiling and you can see the various supply registers. The return comes down a few feet and 90's the opposite way for about 10 feet or so, but there are no air grilles on the sides, bottom or end, so they would have to be on the ceiling facing top of the return trunk that is running paralell to the ceiling. I don't know why anyone would do that, but the alternative is that somebody forgot to cut in return grille openings and the RTU is getting all of its return air from its economizer.
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  4. #4
    Join Date
    Mar 2004
    Location
    Chester County PA
    Posts
    428
    You would have to go up there and see. You could test it but shutting the economizer and see what happens to your airflow.
    Typical poor distribution for RTU's.
    "That motor's done, he let the factory smoke charge out!"

  5. #5
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    I called my old boss who said he will send someone over there to check it out when they are in the area. He said it sounded screwy also. The only reason I could see for placing the grille facing the roof would be sound reduction 'cause the return trunk is so short.
    An answer without a question is meaningless.
    Information without understanding is useless.
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  6. #6
    Join Date
    Nov 2004
    Location
    up in the hizzy
    Posts
    1,441
    I'had seeing it facing up, with a screen on top (plugged up with lint). The outlet mall in Niagara falls has some stores set up that way.

  7. #7
    Join Date
    Apr 2012
    Location
    Paper Street Soap Company
    Posts
    2,304
    It might be a very big sound boot.

    So it would be on top pulling in nice hot return air.

    Ive got a split set up that way. Txv running high superheat because its pulling ine heat from the underside of a metal roof.

  8. #8
    Join Date
    Oct 2005
    Location
    B.C. Canada
    Posts
    904
    Ive seen them facing up before, it was done for noise reduction, that being said i would defanitly go up and have a look

  9. #9
    Join Date
    Nov 2004
    Location
    Austin, TX
    Posts
    888
    I've seen a lot of RTUs that draw the air from the top side of the return duct. Pulls in the warmest air to cool. Have a building with about 12 of them installed that way.
    “I am for doing good to the poor, but...I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it. I observed...that the more public provisions were made for the poor, the less they provided for themselves, and of course became poorer. And, on the contrary, the less was done for them, the more they did for themselves, and became richer.”
    ― Benjamin Franklin

  10. #10
    Join Date
    Jul 2006
    Location
    Anytown USA
    Posts
    2,064
    I see it all the time like that..

    Get up there and look at a few sometimes, they are usually very dirty because no one ever looks at them.

  11. #11
    Join Date
    Jun 2012
    Location
    Queens, New York
    Posts
    66
    Maybe their using 100% outside air. I have a few units here in NY like that.

  12. #12
    Join Date
    Jan 2008
    Location
    Dallas ,Texas
    Posts
    3,725
    Quote Originally Posted by valdelocc View Post
    I'had seeing it facing up, with a screen on top (plugged up with lint). The outlet mall in Niagara falls has some stores set up that way.
    Yep I bet that the return is facing up. Changed out 2-50 tonners this past weekend and both were like this.
    UA 100

    It takes three people to do anything around here. Two do the work, one explains to the crowd of people who showed up when they seen smoke and flames.

  13. #13
    Join Date
    Dec 2008
    Location
    Buffalo NY
    Posts
    3,145
    Quote Originally Posted by valdelocc View Post
    I'had seeing it facing up, with a screen on top (plugged up with lint). The outlet mall in Niagara falls has some stores set up that way.
    I love some of the RTUs at that mall. I saw one this last winter that was melting the snow on the roof because it was not set on the curb right.


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