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Thread: No visible return grille?
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06-19-2012, 02:55 PM #1
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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?
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06-19-2012, 03:41 PM #2
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If it was above a grid then most likely a common plenum with returns in the light fixtures.
Very hard to spot.
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06-19-2012, 03:52 PM #3
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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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06-19-2012, 04:01 PM #4
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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!"
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06-19-2012, 04:33 PM #5
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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.
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06-19-2012, 04:46 PM #6
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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.
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06-19-2012, 04:58 PM #7
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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.
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06-19-2012, 04:59 PM #8
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Ive seen them facing up before, it was done for noise reduction, that being said i would defanitly go up and have a look
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06-19-2012, 05:32 PM #9
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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.
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06-19-2012, 08:08 PM #10
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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.
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06-19-2012, 08:18 PM #11
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Maybe their using 100% outside air. I have a few units here in NY like that.
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06-19-2012, 08:42 PM #12
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Yep I bet that the return is facing up. Changed out 2-50 tonners this past weekend and both were like this.
Originally Posted by valdelocc
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.
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06-19-2012, 08:45 PM #13
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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. Originally Posted by valdelocc
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