AC fans - type and how many CFM? - Fiberglass RV

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Old 08-24-2012, 11:11 AM   #1
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Name: Eric
Trailer: Scamp 13
Posts: 255
AC fans - type and how many CFM?

I'm adding AC to my 13' scamp. Roof mounted was my first choice (expensive, but didn't want to lose storage), but it doesn't sound like my 2009 Scamp was designed to support it. I intend to vent it out the floor. Hot air wants to rise, so forcing it out the floor is going to take a fan.

My question is how many CFM do I need. I know there are a lot of variables that largely depend on how much hot air I need to remove and how much "air resistance" I have due to not having perfectly open flow. I am debating a ~100+ CFM vs. a 200+ CFM fan. I am leaning the 200+ CVM fan just to be safe. Anyone have any real world experience to guide my choice?

Also, I hear of numerous people using the 3-5" muffin fans. Does anyone have experience with the blower fans favored by the marine industry and reasons why to choose one over the other? (example blower link)

Thanks for the help (as always)!

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Old 08-24-2012, 02:37 PM   #2
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Name: Mike
Trailer: 1984 13' UHaul
Posts: 543
It just needs to be vented. Duct work to isolate the out going air

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Old 08-24-2012, 07:18 PM   #3
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Name: Eric
Trailer: Scamp 13
Posts: 255
I was planning on separating the hot from the cold air. I will also measure the air temperature when I am done to make sure it is not overheating. But I have heard of some others using fans an was curious what they had used.
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Old 08-24-2012, 07:39 PM   #4
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Name: Norm and Ginny
Trailer: Scamp 16
Posts: 7,334
AC air management

I'm not an AC expert but here's what I did.

I mounted two 4 or 5" square computer muffin fans behind the air conditioner that blow the hot air thru the floor. I believe they're rated for 100cfm each. As well the airconditioner has an exhaust fan that pressurizes the added exhaust fans.

The cool air that blows thru the exhaust coils is driven by the AC's rear fan. The cool air for this comes from near the center of the trailer via a thin plenum box that feeds through a separate hole.

The output exhaust and the input air for the exhaust are isolated by foam pieces between the AC unit and the closet wall.

Of course the AC has a second fan that pulls air into the cooling coils and blows air out the front.

We have a 5000 btu AC. It draws 4=5 amps when running and is adequate to keep us cool. We do use a small fan in the trailer to blow cool air about.

I think there's pictures of what we did under Preparing a 1991 Scap 16 under Modifications.
Norm and Ginny

2014 Honda Odyssey
1991 Scamp 16
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Old 08-24-2012, 07:55 PM   #5
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Name: Eric
Trailer: Scamp 13
Posts: 255
Norm, Thanks for the information. I read your entire thread a couple of times and enjoyed it. I remembered you had settled on the two fans, but didn't know the CFM. Thanks!

We have a 5000 BTU AC as well. I can't figure out how to do the closet install through the floor in the 13' due to the wheel well. However, I am attempting to design something to go under the front couch in the center.
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