Roof Top AC Units

[Stu & Filo. T]

Getting to the point in my conversion where I'm going to be piecing the interior together, One of my plans is to have 50amp service with 3 DUCTED low profile roof mounted Ac Units, My neighbor thinks thats overkill & that 2 will be more than sufficient, I've got 2in of insulation on the floor with 1 & 1/8" T&G subfloor & will have 2 & 7/8" of spray foam on the walls & ceiling. All windows have been removed & skinned over & I'm installing tinted RV Windows where needed.

Whats been the outcome of other members? 2 units wish you had gone with 3, 3 would have been happy with 2,Wish you'd never started in the first place?? what are your thoughts.

[cadillackid]

I would put in 3 and here's why... unlike an oversized house system, with multiple units you can turn on as few or as many as you need for a particular situation...

you may find that at night once the bus is cooled down that 1 can maintain it.. but if you were out all day and had shut off the genny or were parked without shore-power.. then kick all 3 on and cool it down nice N quick...

you can still maintain humidity by turning off one or 2 if you are over- capacity..

those phoenix 120 degree days in summer if you happened to travel that way are gonna require more than you think to keep cool..
-Christopher

[Njsurf73]

I wonder. If you can afford 3, you may find that 2 does the trick most/all of the time... But having a third for backup or the couple of times a year that extreme temps show up (unless you have extremes all the time).

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[Stu & Filo. T]

Originally Posted by Njsurf73

I wonder. If you can afford 3, you may find that 2 does the trick most/all of the time... But having a third for backup or the couple of times a year that extreme temps show up (unless you have extremes all the time).

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I've seen higher priced S&S's running 5 Units, there will be times when we'll be in extreme areas plus humidity, As long as I'm able to take the edge off during the day I can cope but I need to be comfortable when I sleep. Since I'm going to be ducting I want to do it right the first time.

[Hvbuzz]

I started out with one 15,00btu roof top AC. 1 inch styrofoam in the flor walls and 1/2" with the factory fiberglass in the ceiling. Parked and not driving one did pretty good in 90+ high humidity. Black bus, 4 rv windows. Eventually the 1/2 on the ceiling let loose from the wrong glue so I took it down. Ever since then it struggles with 1 AC in 90+ temps. I did add a second 13,500 rooftop and can run both off my old onan genny, while runnning down the road. Makes it pretty comfortable. Only running the one down the road at those temps gets pretty warm. I made the mistake of only doing a 30 amp shore power service and should have done 50 amp.. That will change soon in the next couple years. Long story short, go 3 and you won't regret it. It's easier to plan for 3 now, then to try and add another later.

[Stu & Filo. T]

I sent a text to an old Air Force buddy who has a 40ft Class A with 2 AC units & he tells me he's happy with the two, spends most his time between Texas & Florida plus the bus is going to be far more insulated than his RV.

[JDOnTheGo]

I had two 13.5 BTU AC's in my 40' Newmar Dutch Star and always found them sufficient. I did avoid terribly high temperatures though. I'm planning two 15K units in my bus. If you plan to be 'in the heat' planning for three AC units seems like a wise choice.

[Njsurf73]

Originally Posted by Stu & Filo. T

I sent a text to an old Air Force buddy who has a 40ft Class A with 2 AC units & he tells me he's happy with the two, spends most his time between Texas & Florida plus the bus is going to be far more insulated than his RV.

Where are you sourcing them from?

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[Stu & Filo. T]

Originally Posted by Njsurf73

Where are you sourcing them from?

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Shopping eBay & Amazon

[cadillackid]

camping world up here just had a big sale on A/C units.. im sure the sales are regional, but seems they advertise every few weeks in summer for having A/C units for sale.. maybe their prices are too high? their biggest gimmick now is the "get a brand new motorhome for $499 a month out the door 0 down..
-Christopher

[BlackJohn]

I'd go three and place them strategically throughout the bus depending on your floor plan.
Besides you have backup if any should fail at some point. Get the hard work done by installing all three at once and have no regrets.

John

[Rusty]

Mike has pair of 15k units in a 40' sprayfoam, no windows bookmobile. Works good enough for me.

When calculating loads for AC , consider windows (size, panes & direction facing), insulation and people.

Single dude in a RV puts off a lot less heat than family of 6. Engine running will add to thermal load. Vehicle color will have impact.

That being said, I'm probably going to add even more insulation as it is cheapest long-term solution to thermal migration.

[Robin97396]

Amen to that. In this one winter I recaptured about 65% of the cost of insulation with reduced heating bills. That sounds good for normal circumstances, but this was an unusually severe winter in this area.

[PNW_Steve]

On my last bus we insulated with 1.5" of spray foam in the walls & ceiling. We installed two roof airs (12.5k) and they kept us cool until outside temps passed 110F.

We spent plenty of time in the Mohave Desert in August and saw temps run in the mid to upper 120's for weeks at a time. I would have killed for a third AC at that time.

On my next bus I am going to install similar AC capacity. I will NOT be visiting AZ in August though......

Equip for the climate you will be spending time in. If you see yourself traveling in extreme climates be prepared. If, like me, you will be in the North during the Summer and South in the Winter then 3 AC's would not be needed.

[Stu & Filo. T]

Originally Posted by BlackJohn

I'd go three and place them strategically throughout the bus depending on your floor plan.
Besides you have backup if any should fail at some point. Get the hard work done by installing all three at once and have no regrets.

John

Yea I've always been the type where I rather have it & not need it than need it & not have it, But it is another $1000.00

[cadillackid]

Originally Posted by Stu & Filo. T

Yea I've always been the type where I rather have it & not need it than need it & not have it, But it is another $1000.00

then run the wires for it and leave the roof space for it... if you cant swing the $1000 now but find you need the A/C later then its just a matter of cutting a hole and dropping a unit in.
-Christopher

[chev49]

I have two 13.5 on roof.... and in the wall small window unit above the head of my bed in the back of the bus, which vents out in the small room for the washer n storage above the engine compartment... Nothing like cool air while one snoozes. Wish I had done this trick on the other 4 busses i converted over the last 30 yrs..

[Dog Rescuer]

How challenging (for the sheet metal challenged) would it be to cut 14" x 14" hole in the roof for a roof vent? I didn't want to cover the emergency hatches just yet...
I need a roof vent in the hotest of ways!

Originally Posted by cadillackid

then run the wires for it and leave the roof space for it... if you cant swing the $1000 now but find you need the A/C later then its just a matter of cutting a hole and dropping a unit in.
-Christopher

[chev49]

v ery easy to cut a hole in the roof... however i make one side next to a roof rib for support. Also quite easy to cut the side of the bus out and install a rv door with its frame. In the case of a bus with lower compartments, the compartment floor is the first step for the stairs, and the floor has to be cut out as well. If i do another bus, i will do with the roof as i have seen one bus. Cut it off same as for raising, save it for a run to the crusher, and use new tubing and steel sheeting to make flat roof. Then inside is nice and square like a house ceiling. Is an extra 1k or so for steel, but so much easier to work with instead of the rounded ceiling, the escape hatches, speaker holes and so forth.

[Booyah45828]

Originally Posted by Dog Rescuer

How challenging (for the sheet metal challenged) would it be to cut 14" x 14" hole in the roof for a roof vent? I didn't want to cover the emergency hatches just yet...
I need a roof vent in the hotest of ways!

It's really simple. I used a hole saw in a drill and a set of good tin snips to cut the hole(both left and right cut snips are a must). I put mine in the middle of the roof ribs and then went overboard and welded a 3/16 inch thick square plate for the gasket to sit on(I wanted it to be as flat and sturdy as possible). I also inserted 2x2 wood in between the inner and outer skins and ran 2" screws from both top and bottom to hold it all together. Mine has 0 movement, and also 0 leaks