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Old 05-29-2016, 08:18 PM   #1
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New and have an a/c question

I have a 1992 International 3800 with a Carpenter Bus Body that is converted. It currently has a portable a\c that doesn't work very well. I want to go with a roof top unit. It is a full size bus with the last 8 or so feet walled off for use as storage (not cooled). Will one 15k btu roof top u it work to cool the bus? I'm in Texas and I like it to be very cool! Thanks in advance
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Old 05-29-2016, 09:18 PM   #2
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Originally Posted by Jhughes08 View Post
I have a 1992 International 3800 with a Carpenter Bus Body that is converted. It currently has a portable a\c that doesn't work very well. I want to go with a roof top unit. It is a full size bus with the last 8 or so feet walled off for use as storage (not cooled). Will one 15k btu roof top u it work to cool the bus? I'm in Texas and I like it to be very cool! Thanks in advance
That entirely depends on your buses dimensions. However, if you have what i am assuming is 30 feet of livable space. No, you will need more cooling my skoolie of 21.5 ft by 7.5 ft wide by 6.2ft tall would use 15k btus to maintain cooling. Also as it is Texas you will probably need even more than normally recommended as the heat is at a higher temperture more consistently. Google btu to cool a space, you should see a few sites that have instant calculators. This will give you a rather accurate number on required btu's.
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Old 05-29-2016, 10:50 PM   #3
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depending on how many rows you have you will want 2.. and im assuming this is just for when you are parked.. if you want rooftop units to cool you while driving good luck... lots of engine and road heat is introduced into the bus when moving down the freeway at 65...

it also depends on how well your conversion was done when it comes to insulation.. and how quickly you want to cool it.. if you want to leave your bus shut-down all day (generator off).and cool it down quickly when you come home to it.. that also affects how much cooling you need..

if you are looking to cool it while driving you may need a unit that blows into the driver compartment.. maybe you keep that portable for that? or install Dash-air...

-Christopher
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Old 05-30-2016, 09:55 AM   #4
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I'll measure and take a few more pictures today. If I went with one unit I was going to put it in the front and **** the door to the back while driving. I think I'll do one now and then add the second later due to cost. I appreciate the responses, I'm very excited to have this resource.




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Old 05-30-2016, 10:50 AM   #5
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it also depends on how well your conversion was done when it comes to insulation.. and how quickly you want to cool it.. if you want to leave your bus shut-down all day (generator off).and cool it down quickly when you come home to it.. that also affects how much cooling you need..
Insulation is a huge key. Some converters don't pull any of the panels and leave the old insulation in place. Not only is the old fiberglass inefficient, but leaving the steel panels in place creates a huge thermal bridge that allows all your cold back out into the rest of the world, forcing the AC to work even harder. And if the wall between the living and storage space isn't insulated either, you have the same problem- a huge thermal bridge, forcing your 15k btu AC to work harder to cool the space in the bus.

A second key thing to remember is the roof. Is it white/reflective color or does it have a deck on top? Because if the answer is "No" to either, and you've left your bus out in the Texas sun all day, you're also forcing your AC to work harder to cool off that space.
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Old 05-30-2016, 11:25 AM   #6
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initial core cool down is the toughest thing your A/C will endure... you can drop the air temperature a few degrees fairly quickly.. and with Dash / road air you have the advantage you are blowing cold air on your body so you feel cool..

once the air begins to cool a few degrees.. then that air begins to take in the heat of the surrounding items on the bus... the reverse of radiant heating... your air now becomes the heat exchanger medium .. those core parts hold a lot of heat... metals.. woods, plastics, etc.. as azules mentioned, once you start cooling those parts down is where insulation and sun-shield becomes key..

unlike dash air, when you are parked, you are living in your bus more like a home and therefore want the core cool, not just the air.. thus when you sit in a chair, lean against a wall.. are away from the air unit itself you want to be cool.. (or warm in winter)..

in a home some of this is overcome because your A/C is often just turned on all the time so the core temp stays cool and the A/C has a fighting chance during the heat of the day by using the cool core to its advantage..

thus why I ask how you are planning to use the bus? if you plan on running the air even when you are away from it (but going to return later in the day).. or do you shut it off? if you are planning to run on the road alot, then you have engine heast to overcome.. and will likely want either a dash air.. or that portable up front to keep the driver cool.. those big windshields and engine bring in a lot of heat...

you will also want to seal up air leaks from your engine compartment.. dynamat the floors and firewall inside.. insulate and seal the dog-house, close your heater valves under the hood.. (or install electrically operated ones).. and Close the outside air intake for the defrosters.. (normally a lever on the driver console... oftentimes frozen open, so you will need to disassemble the heater box around the driver (good idea anyway).. and repair that air flap door...

-Christopher
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Old 05-30-2016, 08:25 PM   #7
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I'm going to use it as a camper only. So when I am using it the ac will stay on. I'd like to shut off the front and use one unit while driving. Me and my grandfather did this bus about 10-15 years ago. We used foam board in the walls and in the back wall then spray foamed the edges. Then ceiling insulation was not changed out so its the fiber glass. I'm am about to put a white thermal rubber type sealant on the roof that is supposed to seal and block some heat. I am going to also paint the firewall with it to help with engine heat. No windows were removed so I know that's a lot of heat transfer.

<iframe width="480" height="360" src="http://s1079.photobucket.com/user/jhughes08/embed/Mobile%20Uploads/story"></iframe>
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Old 05-31-2016, 04:34 PM   #8
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here you go

http://www.skoolie.net/forums/f10/ho...-op-11846.html


I did a step by step for photobucket
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Old 05-31-2016, 07:45 PM   #9
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Mobile Uploads Slideshow by jhughes08 | Photobucket
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Old 06-01-2016, 03:07 AM   #10
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That appears to be a Mitchell, IN built Carpenter bus. I have one as well (older model). These buses had some issues with faulty welds where the roof bows meet the tops of the windows, unfortunately since Carpenter is no longer in business and the problem was not discovered until after the fact, there's no real way to force a recall. Not all had this issue, I suppose it depends on who was doing the welding that day it was built. It probably won't pose any issue as long as it isn't involved in a rollover (which was how the problem was discovered in the first place).
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