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Old 03-13-2020, 05:39 PM   #1
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how many btu to cool 40 ft bus

Im new in planing stage but i live in AZ how much aid condition does it take to keep a 40 ft bus cool
thanks in advance
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Old 03-13-2020, 07:07 PM   #2
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Probably a tough question to answer. There are many variables. Such as, are you eliminating windows? Adding insulation? Roof painted white?
I would imagine to cool a metal tube under the AZ sun would be a challenge.
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Old 03-13-2020, 07:14 PM   #3
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You should find this thread valuable
https://www.skoolie.net/forums/f9/th...a-c-27952.html
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Old 03-14-2020, 08:47 AM   #4
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You should find this thread valuable
https://www.skoolie.net/forums/f9/th...a-c-27952.html
Thank you I would have never thought it would take that much ,now I'm thinking leaving bus air in,
Then maybe 1 mini split in bed room and 1 in liveing Ares for when the bus is not running.
Thank you for thank you for the link.
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Old 03-14-2020, 10:21 AM   #5
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Unless you are talking powered campsites

your focus should be on extremely tight and thick insulation of as small an area as you can stand.

Powering aircon off grid gets **very** expensive, fast.
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Old 03-15-2020, 03:12 PM   #6
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Unless you are talking powered campsites

your focus should be on extremely tight and thick insulation of as small an area as you can stand.

Powering aircon off grid gets **very** expensive, fast.
I was thinking just bedroom maybe 8×6 at night and maybe a area about the same size up front??
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Old 03-15-2020, 04:28 PM   #7
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12K BTU each might be enough with good & tight insulation, at least when it's not **too** hot out.

Better to have too much capacity and let the duty cycling be controlled by a thermostat

rather than the unit struggling at 100%

Webasto makes a 16,000 btu unit can be powered by a Honda 2000i

but needs an EasyStart 364 to get past the initial surge required.
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Old 03-15-2020, 04:47 PM   #8
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Originally Posted by john61ct View Post
12K BTU each might be enough with good & tight insulation, at least when it's not **too** hot out.

Better to have too much capacity and let the duty cycling be controlled by a thermostat

rather than the unit struggling at 100%

Webasto makes a 16,000 btu unit can be powered by a Honda 2000i

but needs an EasyStart 364 to get past the initial surge required.
thanks for all the info will look into the 16.000 i agree on having more than not struggling. thanks again
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Old 03-21-2020, 03:46 PM   #9
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We have success with only 10K btu with a portable AC unit pushng from front to back. We are only half complete with full insulation and flooring, but with the aid of a box fan to help pull the cool air we do maintain a comfortable temperature inside.
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Old 03-21-2020, 04:18 PM   #10
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Thanks for info I'm thinking compartments closed off by pocket doors like driving and kitchen area as 1
Rear bedroom another l
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Old 03-21-2020, 04:44 PM   #11
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All depends on the temp delta needed

in Arizona or Texas summers 10 BTU hardly puts a dent in it,

vs just a 5-10° difference.

Just shading and ventilation in dry heat can help a lot once you get acclimated, even a "swamp cooler" or ice chest version can make a difference.

But dripping muggy humidity is a different story, places like Florida, Louisiana, the PNW, just move away!
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Old 03-21-2020, 11:31 PM   #12
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In Wisconsin our summers are fairly short and temps rarely get above 75 degrees. It does get humid however.

I see most campers up here even longer goosenecks get by just fine with one 13.5k btu roof AC unit.

Insulation and removing the stock school bus windows will help the most in my opinion. Also paint your roof white if it isn't already so.
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Old 03-22-2020, 01:36 AM   #13
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At Least 25,000

Hi there.
I lived in my 26 foot 5th wheel in Phoenix. (Mesa actually) for 3 years from 2015 to 2018. It required all and I do mean ALL of two AC units that were 14,000 and 8000 BTUs.

That would keep me cool for the most part.
I was thinking of building a 40 school in and I planned on at least two 14,0000 BTU units and a 5000 window unit.

Then I found a really neat mini-split that had a single compressor (condenser) unit and I could add three separate wall units (evaporators) for about 40,000 BTUs of cooling capacity and the nice thing about mini splits is you can get them as heat pumps and they will also heat depending on how cold it is outside. Anyway if you are going rooftop units plan on 3. Two in the common area and one for the main bedroom. That's my opinion and experience.
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Old 03-22-2020, 08:55 AM   #14
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Maybe someone with solar panels can chime in on this... I think if you install solar panels on the roof that stand off a little then they absorb both sunlight for energy and the corresponding heat which reduces the solar heat load on that 400 square foot metal roof. It would be about equivalent to parking under a canopy which doesn't change the ambient outside temperature but without the direct sunlight at least your cooling units have a chance. A big metal can in direct sunlight not so much. Anyone with roof solar panels have any insights on this?
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Old 03-22-2020, 09:20 AM   #15
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The underside of solar panels do emit a **lot** of radiant heat from the PV conversion process.

A larger gap helps a bit, but that's not ideal for driving.

A tilting rack helps more, also increasing solar efficiency a lot.

There have been attempts to capture that waste energy for heating water.

But bottom line, you need lots of insulation up there as well as a white surface.
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Old 03-22-2020, 10:40 AM   #16
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The underside of solar panels do emit a **lot** of radiant heat from the PV conversion process.
I hadn't thought of that. What is a lot? I would think it would be a lot less than heat generated by the sun on a white surface. That can easily reach temps of over 100° F on a sunny day.
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Old 03-22-2020, 10:46 AM   #17
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more.

can't keep your hand under there

enough to peel paint poorly done

I'm sure varies by type
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Old 03-22-2020, 01:14 PM   #18
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more.

can't keep your hand under there

enough to peel paint poorly done

I'm sure varies by type
Well carp! That ruins my aspirations.
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