AC on mini bus.

Guysakar · 01-09-2014, 03:23 PM

Hi all, brand new to all of this and just trying to get my ducks in a row before I start making purchases.

I am looking to get a smaller bus (like the image below) and convert it. I originally was going to go with a window unit (8K BTU) but everyone keeps saying that it wont be powerful enough to cool it off in the hot summers of the south, so I am opting for a Coleman Mach 3 (likely the PS).

My concern is how difficult it will be to install on the roof. If it were a standard size school bus I could easily make a brace, but the roofs of these smaller buses don't seem to have the same frame work as a full size. Most of the ones I have looked at don't really seem to have any frame/support on the roof other than a joint of some type in the middle (I am going off of images at this point).

Anybody have any ideas or experience with this type of thing? I would really, really appreciate any advice.

Tango · 01-09-2014, 04:35 PM

Howdy Guysakar, and Welcome to the Funny Farm --- You will no doubt get a variety of responses and opinions regarding A/C units here so I'll go ahead and kick start the confusion. Personally, I've had a couple of Coleman rooftop units over the years and have never been impressed or satisfied with them. They are way too expensive for what they are and from my exposure have pretty lousy and expensive service records. The 13,500 rating both of mine had was fantasy as they never put out anything like "cold" air which a unit that size should. This time around I'm going with a little high efficiency 8,000btu window unit. I have tested it on my little Honda generator and it does make lots of cold air and without even kicking the gen-set above idle. Much more than either of my rooftops ever did. And the fact that I can fully replace this unit just about anywhere in the country for less money than what most RV shops want just to "look at" the average rooftop closed the deal for me.

That said, the other issues are insulation and air-tightness. It doesn't really matter how much cold you are pumping, if it is leaking out faster than you can make it, your rig will never cool down or stay that way. And you'll find quite a range of ideas & opinions on those topics here as well. Just sort through them, keep in mind your skills and budget and goals and you'll wind up with a plan of your own that fits your dream.

OK...I'll move aside now and let some of the other folks here jump in. But do keep us informed on how things progress. Best of luck on the "Hunt".

sdwarf36 · 01-09-2014, 06:49 PM

Heres a pic of the roof structure of my shuttle bus. There is plenty of support.

Guysakar · 01-09-2014, 07:06 PM

Quote:

Originally Posted by Tango

Howdy Guysakar, and Welcome to the Funny Farm --- You will no doubt get a variety of responses and opinions regarding A/C units here so I'll go ahead and kick start the confusion. Personally, I've had a couple of Coleman rooftop units over the years and have never been impressed or satisfied with them. They are way too expensive for what they are and from my exposure have pretty lousy and expensive service records. The 13,500 rating both of mine had was fantasy as they never put out anything like "cold" air which a unit that size should. This time around I'm going with a little high efficiency 8,000btu window unit. I have tested it on my little Honda generator and it does make lots of cold air and without even kicking the gen-set above idle. Much more than either of my rooftops ever did. And the fact that I can fully replace this unit just about anywhere in the country for less money than what most RV shops want just to "look at" the average rooftop closed the deal for me.

That said, the other issues are insulation and air-tightness. It doesn't really matter how much cold you are pumping, if it is leaking out faster than you can make it, your rig will never cool down or stay that way. And you'll find quite a range of ideas & opinions on those topics here as well. Just sort through them, keep in mind your skills and budget and goals and you'll wind up with a plan of your own that fits your dream.

OK...I'll move aside now and let some of the other folks here jump in. But do keep us informed on how things progress. Best of luck on the "Hunt".

Thanks for the reply. I was really wanting an 8K BTU wall unit, but everyone keeps saying (without empirical evidence is seems) that you need a 13K roof unit at a minimum.

I wanted to go with the Honda 2K EU and the Frigidaire 8K on Amazon. It is rated at around 800 watts so that is exactly half load on the Honda 2K. Which Honda are you running?

I would love to find some empirical evidence of how well the 8K wall units cool down smaller rigs.

Thanks again.

LuckyChow · 01-09-2014, 07:23 PM

Most of these have a fiberglass roof or frp board. All I have ever seen have metal framing under the roof supporting it. If it's not obvious, you can figure out where the framing is by using an ordinary stud-finder (not Kim Kardashian ) from the local big box.

Guysakar · 01-09-2014, 07:28 PM

Quote:

Originally Posted by LuckyChow

Most of these have a fiberglass roof or frp board. All I have ever seen have metal framing under the roof supporting it. If it's not obvious, you can figure out where the framing is by using an ordinary stud-finder (not Kim Kardashian ) from the local big box.

I bet it's huge.

Tango · 01-10-2014, 09:36 AM

Below is a link to the "Energy Star" page that has a chart on sizing A/C systems. This is what I went by. An 8K BTU is just right for 300-350 sf. That would be a bus about 40 feet long (8' x 40'= 320 sf). My "living area" is only about 120 sf. so in reality a 5 or 6K unit would be plenty.

http://www.energystar.gov/?c=roomac.pr_properly_sized

And my Honda genny is the 3K. Like I said, the A/C cranks out plenty of cold without the genset ever coming off idle.

BTW...if you are shopping A/C units, do check the "Energy Star" rating. The new units are remarkably efficient.

bansil · 01-10-2014, 10:59 AM

I will add this:

Nominal insulation on lower 1/3 walls nothing else...stock...8ft x 12ft bedroom....5500 btu window unit = ice box even in full sun on a 95* day in TN/NC

your mileage may vary....on low you shiver naked

roach711 · 01-11-2014, 04:50 PM

My 2001 Aerotech looks almost identical to the one you posted and had a big honkin' AC condenser mounted on the rear of the roof. They used 1 1/2" aluminum angle iron "feet" on both sides to spread the weight and bolted it through the roof with 1/4" bolts and big flat washers inside.

I've found some plywood glassed into the body running the length of the bus at the peak of the roof and some in the walls where the seat rails screw to the bus. I completely stripped the inner trim panels and I've never found any steel bracing in the body at all.

The fiberglass body is pretty rigid and I wouldn't hesitate to put an RV AC unit up there. I weigh 180 and the roof holds me fine.

ol trunt · 01-11-2014, 08:26 PM

I purchased the same Frigidare 8K a/c from Amazon. The unit seems to cool just fine sending out 20 degree F gusts. The unit seems to be noisier than what I recall of my roof mount 13K and it will probably wake me as it cycles on and off. The extra noise seems to be a theme with these energy star units as you will find when you read the coments people have posted about various brands. Make sure to buy a unit backed by Amazon--they are very good about return of damaged goods and several of the general sellers aren't so good. The first a/c Amazon shipped came in a flimsey cardboard box with no packing. The unit looked like it had been tossed from a moving UPS truck a couple of times and promptly let out all its smoke as soon as I pluged it in--Amazon took it back without a problem and I ordered another. The second unit was missing a few parts though none I cared about and had to be taken apart to unjamb the fan and pound out the dents in the case. Fortunately the plastic front survived shipment and none of the dented areas will be noticed by a scared nun trying to get out of the cross walk as I drive down the street.

I guess I could have sent the second unit back but it seems to work just fine and I don't want to press the "third times the charm" theory. Tango and I have pretty much the same busses. He may have tested his a/c in the Texas sun by now so you might ask him what he learned. I tested mine on a 70 degree F day but not in the direct sun and the thing froze me out.

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