roof top A/Ci nstallation

busshawg · March 23, 2009, 11:35:50 AM

I will probably be installing another roof top. I have noticed in quite a few pics that some of you have installed these units on one side or the other of the main beam that runs down the centre of the bus's roof. The last one I installed I cut the centre beam and constructed new framing. My question to you guys is do these units work well on one side or the other of the main beam, as it wouldn't be sitting level. If they do work well in this fashion I would consider putting one up closer to the drivers compartment.

Thanks

H3Jim · March 23, 2009, 03:53:50 PM

My roof is pretty flat, but they work really well. The instruction say that it can't be more than 7 degrees from level. I suppose if I was parked on a slant it could become an issue.

Another idea, depending on your specific airconditioning unit is to leave the center rib in, the air will just flow around it. I have 3 Carrier low profile units, one regular mount, the other two I constructed the ducts. For these two you could leave the center rib in, but the unducted (built in) would not because of the placement of the cool air duct. The mounting bolts in the 4 corners do not interfere with the center rib, so its only the placement of the duct that is the determining factor.

One other bonus came from putting the units slightly off center is that I had just enough more roof space on one side to mount the solar panels I bought. Since I have front to back lateral arm awnings that take up about 6" along the edge, those few extra inches provided the space for two of my 4 panels.

Nick Badame Refrig/ACC · March 23, 2009, 06:17:37 PM

Hi Grant,

They will work on an angle however, they are designed so that the condensate water produced by the air conditioner will flow

into the the outside pan in the condencer area. This cold water is then picked up by a sling ring on the condencer fan blade and thrown

onto the condencer coil for added cooling of the hot gas in the coil. If the water is not presant there, on extreme hot days you

may not cool your coach as well as others do.

Good Luck
Nick-

TomC · March 23, 2009, 10:27:15 PM

I have three roof airs positioned on either side of the center beam since I figure the engineers know more then I do about strength. The front one is on the right side of the beam to be able to aim better at the drivers seat. The second one it in the middle offset to the left that lines up with my offset to the left hallway. And the third it over the bed also offset to the left. I usually go down the road on the front and rear one, and use the center for when parked. With my transits relatively flat roof, drainage has not been an issue. In fact the three Coleman 13,500btu A/C's have been 100% reliable since I installed them in 1994. Good Luck, TomC

busshawg · March 24, 2009, 07:34:09 AM

Thanks guys, sounds like I should probably stay with centre mounting them as the roofs on these MCI's are quite round. I do like the idea of leaving the centre beam in though, never considered that. Actually I wish I had asked this question before I installed my original one. Just the ducting to worry about.

Thanks again.

H3Jim · March 24, 2009, 07:59:54 AM

I guess one other comment. If the angle is an issue, your can shim the low side up so the unit is level. All it has to do is seal, so you might have to make a wedge, but thats not much.

busshawg · March 24, 2009, 10:16:21 AM

I suppose that would work to. Then I would be into welding a frame in wouldn't I? If I did keep it in the centre and didn't remove the centre beam I could probably get away without building a frame. What are your thoughts

H3Jim · March 24, 2009, 03:41:21 PM

The wedge could be made from wood, its only a spacer and will be compressed when the unit is installed. You'd of courese want to use dicor or some othersealant on it.

The frame depends on how far away any support beams are in the roof. Keep in mind that the bolts that hold it on squeeze the roof and ceiling together. Yes the center beam would give support to the unit. If the edges are floppy, all I did was cut some wood spacers, soak them in urethane and slip them between the roof and the ceiling.

gus · March 24, 2009, 04:22:40 PM

We GMC guys don't have to worry about that big center rib since we have two smaller ribs with space in between to mount rooftops!!

One good hint which I read in a S&S magazine and put to good use is to cut a hole in the plastic housing directly below the air duct in a rooftop AC so the air comes straight down to the floor instead of taking a 90* bend and being diffused. I covered the hole with a louvered floor vent cover from HD and it looks as if it was made that way.

My 4104 went from unbearable in really hot sunny weather to bearable and even comfortable sometimes! My biggest problem is the fwd AC is too far aft to really cool the driver and the aft AC is too far aft to really help the front.