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Old 06-16-2016, 06:03 AM   #1
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Beat the heat - improve air flow from ceiling AC unit

I’ve always had a concern about the roof top AC unit. It seemed like it doesn't put out the quantity of air that it should.

Last week I was removing the AC unit in preparation for re-coating the roof. I looked carefully at how the air flow is routed, and wasn’t happy with what I seen.

With the ceiling cover off I ran the AC unit. The large squirrel cage blower delivers a lot of air, straight down toward the floor. However, when the ceiling cover is installed, the air enters into the ceiling unit, and is restricted by abruptly 90 degree turn and a 2 inch restriction. the air then takes several more 90 degree turns before it exits out the vents on each end.

What the cover really needs is a vent opening just below the blower that allows the air to shoot straight down toward the floor, unrestricted.

See entire article with photos below.

Beat the heat – Improving air flow from the air conditioner ceiling unit | 2001 Coachmen Mirada 300QB

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1999 Fleetwood Southwind 35S (Ford F53 6.8L V10) - Toad 2003 Saturn Vue.

It won't do MACH 2, but I can get a sandwich and take a pee.
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Old 06-16-2016, 08:25 AM   #2
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Interesting project. I have never been impressed with the ducted system and I put some deflectors in my vents to help direct air down where it should be. Seems a lot of the cold air just passes over the openings as they are. When it is hot this could be a good idea to simply blast some good cold air inside the coach for a while and I am going to check it out with mine.

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Old 06-16-2016, 08:44 AM   #3
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I understand some of the newer ducted systems may already have a louvered vent near the intake that does exactly this. My system is unducted and older, and this made a BIG difference.
1999 Fleetwood Southwind 35S (Ford F53 6.8L V10) - Toad 2003 Saturn Vue.

It won't do MACH 2, but I can get a sandwich and take a pee.
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Old 06-16-2016, 01:07 PM   #4
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The plenums for my ducted system have louvers on 3 sides I can open to dump the air straight out. We do this on both units until we get the coach to the desired temp. Once there, we close the louvers and use the ducts.
Brian and Tammy
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Old 06-16-2016, 02:40 PM   #5
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I have what looks like the exact same AC unit. I guess I've got another project now

I assume the thought behind the original design is that it blows along the ceiling, cooling the air that's collected up there. Blowing it straight down would mean that there's more cool air low down, but not a lot at head height. It'll probably cool the coach more effectively anyway, just by virtue of putting out more volume.

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Old 06-16-2016, 03:24 PM   #6
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I have done many variations and it does work., However the noise level can be a pain.

Drop your round registers out and see if they are a bit too long inside the ducts., I trimmed all of mine for a better fit.,

In addition to that I lined the transition area inside the AC's with metal duct tape to smooth out the air flow.

My condensation units need to be cleaned well about every 6 months. I am full time and in Florida so the AC runs a lot.

Myron & Deborah
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ceiling, heat

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