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Old 11-13-2022, 02:28 PM   #1
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Proper Cooling Air flow thru van

I have a panel van with no windows with a 15,000 but AC on the roof, a single Maxx Fan on the mid rear of the van with two 12x12 custom hatches on the roof one in the front right corner and one in the rear left corner as partial vents or have it fully open. My question is what is the proper air flow when i have the AC running, is it to have the fan also running with both 12x12 vents open or leave everything total shut with the maxx fan off and closed when the ac is running.

This is referred to in the summer months only when its hot at 90 degrees out.
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Old 11-13-2022, 04:08 PM   #2
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Run AC...leave roof vents closed

RV AC is a 'closed circulating system'----inside air is cooled and recirculated to be cooled again

Opening Roof vents allows cool air to go outside and hot outside air to come in


Mommy always saud
"close the door we are not trying to cool the neighborhood down
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Old 12-02-2022, 12:28 PM   #3
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Quote:
Originally Posted by CaptainBo View Post
I have a panel van with no windows with a 15,000 but AC on the roof, a single Maxx Fan on the mid rear of the van with two 12x12 custom hatches on the roof one in the front right corner and one in the rear left corner as partial vents or have it fully open. My question is what is the proper air flow when i have the AC running, is it to have the fan also running with both 12x12 vents open or leave everything total shut with the maxx fan off and closed when the ac is running.

This is referred to in the summer months only when its hot at 90 degrees out.
This summer, I did a power test in my self-built van on three 100 degree days (Maxx Air up front, 12v Dometic Roof AC in the back). I wanted to see how much power it would draw on battery alone. My AC is only about 6500 BTUs. I let the van get over 100 degrees before starting the test each day. I did AC alone on day one, fan plus AC at the same time on day two, and AC alone but closing off the bed area on day three (the AC is over the bed). My thinking with the fan was that since cool air sinks and hot air rises, it should evacuate the hot air near the roof while the cool air falls and cool faster. However, it cooled about the same as not using the fan so there was no benefit and it actually used a little more power. The most energy efficient way for me was to open everything up to evacuate the heat so it at least gets to ambient and then cool with the AC alone. And for ultimate efficiency, the lowest power consumption was seen when closing off the bed area so only that area gets cooled (for night sleeping). Once it reached temp (74 degrees) it only took about 17 amps of power to keep the temp stable.
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Old 12-03-2022, 10:25 PM   #4
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Wow great test. I keep my AC on low setting cause it draws about 120 AMPS when the compressor is on during summertime im not sure how much BTU im getting only at low. At high i would kill my batteries real quick. Sealing off the bed area at night is a great idea. I've taken your advice along with others replying back that i close every vent and block the sun from coming through the hatches and maxx fan vent using vent insulators. Thanks for testing and replying back.
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Old 12-04-2022, 07:51 AM   #5
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The compressor draws the same amps on high or low.
High and low are fan motor speeds. Small difference in amp draw.

Roof A/Cs take inside air in and cool it ( actually remove heat ) before sending it back out. No outside air comes in.

Close every other opening to keep the hot air from coming in. The only time you would want some air exchange is if cooking during hot weather.
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