DIY camper conversion costs? - Page 5 - Ram Promaster Forum
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post #41 of 49 Old 01-10-2017, 03:43 PM
seapro
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Is 5000 or 6000 BTU air conditioning sufficient for a well insulated and only one window 159 WB high roof DIY camper? Anyone with experience?
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post #42 of 49 Old 01-10-2017, 04:41 PM
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It should be more than enough to cool a 150SF room in a house so I would say yes although I have no experience cooling van with one

2014, High Top/159 WB, 2500 gas Promaster fully converted for camping.
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post #43 of 49 Old 01-10-2017, 05:00 PM
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Garage
GaryBIS knows how to calculate it. See his calculator here: http://www.builditsolar.com/Referenc...anHeatLoss.htm

2015 136" HT Diesel Sandstone Metallic Born on 6/12/2015 Campervan build see: http://www.promasterforum.com/forum/...ad.php?t=37177
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post #44 of 49 Old 01-10-2017, 05:09 PM
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http://www.inspectapedia.com/aircond...hart.php#Chart

2014, High Top/159 WB, 2500 gas Promaster fully converted for camping.
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post #45 of 49 Old 01-10-2017, 05:57 PM
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Hi,
On an AC size for a 159 WB.

Did a quick run of the heat loos spreadsheet and came up with the numbers below -- you can download the spreadsheet and refine the numbers to what you actually have.
http://www.buildagreenrv.com/design-...n-conversions/

For 90F outside and 70F inside, I get a heat gain of 1200 bTU/hr. To this you need to add about 300 BTU/hr per person in the van, and if you plan to cook in the van add some more for that. So, maybe that gives you about 2000 BTU/hr with two people in the van.

This is for these R values:
Walls and ceiling R11
Floor R10
Windows R3
0.5 air changes per hour

The walls and ceiling could be 1.5 inches of poyiso plus paneling and air layers to get R11. This is somewhat more than most people insulate to, but if you are going to be using AC, its definitely worth it.
Windows are R3 could be a single glazed window with a snug fitting Reflectex shade inside.

Important to have reflective shades on the windows for AC. A window in direct sun can gain 200+ BTU/hr per sqft of windows -- so, 10 sqft of unshaded unreflectorized window would about double your heat gain!

These also assume parking pretty much in the shade -- parking in the sun will increase the gain for the half of the van in the sun as the van skin temp will be high.

If it was 100F outside, then the heat gain wold be about 1800 + 600 = 2400 BTU/hr ish.

So, it seems like a 5000 BTU/hr AC would be fine -- it would have some excess capacity for the initial cool down of a hot van, and it would probably run about half the time or less once it got the initial cool down done.

I think that being able to use a smaller AC (like 5000 BTU/hr) is a winner all around. Smaller/cheaper AC, smaller/cheaper/quieter(?) generator, smaller/cheaper inverter, and able to handle flaky shore power better. Maybe even run a on a big house battery for limited time.
There is probably enough margin to cover situations where you can't park in the shade or some additional miscellaneous internal heat gains.


Another thought would be to close off the cab area with an insulated curtain. This would cut down the heat gain for the large cab windows (but you still want the reflective shades on them).
If it was a good insulating curtain, this might cut heat gain by as much as 25%.

Would be good to hear from someone who has actually tried a 5000 BTU/hr AC in a well insulated van.

600 watts of solar aimed at the sun (not flat on the roof) would run an efficient 5000 BTU/hr AC on a 50 to 75% duty cycle and still be able to charge the house battery some!

Gary

Last edited by GaryBIS; 01-10-2017 at 06:04 PM.
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post #46 of 49 Old 01-10-2017, 06:26 PM
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Fifty years of construction experience tells me 5000 btu's will freeze your (socks) off

2014, High Top/159 WB, 2500 gas Promaster fully converted for camping.
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post #47 of 49 Old 01-11-2017, 10:46 AM
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As a former owner of a Winnebago Rialta with a 8K BTU roof air, the unit had a hard time keeping the insides cool at a comfortable level. In 2015 at Zion NP the temps in the afternoon were about 105*F and even with reflective covers on the windows, the inside temp was about 80*F until late at night. It was like a cave inside, dark and slightly cool. Some Rialta owners installed 13.5K units to overcome the heat inside the unit as the smaller unit had to work real hard to remove the heat.
Even with my new Trend, the 13.5K A/C unit has a hard time cooling the insides in hot climates. This is with double pane side windows and wraparound windshield outside cover with reflective foil. A box fan helps to circulate the inside air to aid in cooling.
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post #48 of 49 Old 01-11-2017, 10:50 AM
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Sonicsix had some discussions about an AC unit mounted under his couch/bed. Seems like 5000BTU mounted low didn't cut it, so he changed to a portable 10,000BTU unit.

More info here:

http://www.promasterforum.com/forum/...401#post248401

I'm still thinking about mounting a 5000BTU unit in my back door window area... removable and affordable (once I take out the existing glass and replace it with an aluminum piece with a hole big enough for an AC unit!)

Ed

Working on the van, and my website about it! Please visit www.empowersites.com/edsvan or here on the forum
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post #49 of 49 Old 01-11-2017, 07:27 PM Thread Starter
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Quote:
Originally Posted by seapro View Post
Is 5000 or 6000 BTU air conditioning sufficient for a well insulated and only one window 159 WB high roof DIY camper? Anyone with experience?


I don't have a PM but can share 10 years of experience with a 5,000 BTU/hr A/C in an extended Ford window van.


My van has a total of 12 windows (including windshield if I counted right), with windshield and front door windows getting covered from outside with vinyl RV cover when parked. Covering the windshield helps tremendously, particularly if sun comes through windshield at any angle.


At night the air conditioner's capacity is not an issue at all. The A/C can cool the van cooler than we want; and even then cycles on and off.


During the day if the van is in the shade, the A/C cools it down enough to make it comfortable by removing humidity, and by dropping the temperature at least 10 degrees or more. Keep in mind that I have lots of windows and essentially no real insulation.


If afternoon sun comes through the windows, particularly on a warm day, then the A/C doesn't keep the van cool enough. It's just too much glass which allows solar heat to overwhelm the 5,000 BTU/hr A/C.


To prevent solar heat from coming through windows and essentially turning the van into a greenhouse, we made vinyl external curtains that hang over the windows to match the one we purchased for the windshield. This makes a lot of difference, and allows the A/C to cool the van enough to be tolerable in Florida summer during the middle of the day. We camped that way at Disney World in summer and left A/C on while we went to park. When we returned it wasn't freezing but was comfortable.


I think that a van with only one extra window (not counting front windows and windshield) that is insulated adequately should stay far cooler than mine. Even though a PM is taller than my extended E-350, the surface area of sheet-metal isn't all that much bigger. My original plan for an Extended High-Roof PM was to have four mid-size double-pane windows (2 per side) plus the rear two windows. By cutting window area almost in half, and by adding some real insulation on all sheet-metal surfaces before building the interior, I think a 5,000 BTU/hr A/C will be good enough for us. On occasions the temperature could get a little warmer than one likes, but I can deal with that as part of camping (a little roughing it is OK). On the other hand I don't plan to camp in Death Valley when it's 120 F outside.
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