Over The Road Air Conditioning

[Fredward]

Sitting here in Minnesota in the dead of winter, I am trying figure out why my coach was so hot inside last summer. Its an MC-5 with 8" roof raise and Hehr RV style windows. Two 13,000 BTU roof units and a 7K Kohler generator. Bus air was removed by PO.

When we were parked, we had plenty of cool air but going down the road on 90 degree days, the two roof units barely would keep it 86 inside. How can I fix this problem? Would adding a driver's air (automotive style) help? Or do i need basement air? or is bus air the only way to really keep one of these things cool.

Fred

[Nick Badame Refrig/ACC]

Hi Fred,

I would intice you to look into a dash system which runs off your engine.

Look in Red Dot's site or even call them, they are very helpfull with set-up information.

OTR engine A/C is going to be the only system powerfull enough to overcome the heat gain that

the wind and the sun creates while under way.

Good Luck
Nick-

[cody]

Good information nick, we have that problem too, on the road the bus gets pretty warm inside, can you post the red dot site for us?

[Kwajdiver]

I open the windows, but watch the paper towels.

Bill

[TrevorH]

So if one purchased a bus with a fully functional OTR air system would it be beneficial to them to keep the system for use during driving.  Then have a second system for while parked?  I was considering removing the OTR system to get some funds for other projects, would this be a good idea?

[Nick Badame Refrig/ACC]

Hi Guy,

Try this

http://www.rdac.com/Pages/product_pages/units_pages/5075_unit.html

or this
http://www.rdac.com/Pages/product_pages/units_pages/5040_unit.html

Nick-

[chris4905]

If the temps are high it's very difficult, if not impossible, for the roof air(s) to keep the coach comfortably cool.  Just too much heat in through the front windshield.

The front roof AC can be run of course by the generator, or a systems which allows the AC to be run though the Inverter and the big engine alternator/generator recharges the batts while going down the road, faster than the front AC can run them down.

Some people place a temp barrier directly behind the front air, such as a sheet or blanket.  The sheet is hung from the roof and stretched from wall to wall.  Works so well for some, they use it all the time during high temps.

If nothing else it will give some comfort till you decide "your way" for permanent.

[DavidInWilmNC]

I realize maintaining an OTR system, getting it to work in the first place, can be expensive.  The general suggestion for converters is to remove the OTR air.  I kept mine, and it works great, but I do have to add R134a each year.  How cool do buses that rely on 2 or 3 roof units really stay on a hot day, driving down the road, facing the sun?  Even a couple pounds low on refrigerant my OTR air will freeze the front 2/3's of the bus (the back 1/3 is comfy) on a hot July day in Georgia on the interstate.  I didn't even use the dash air.  Maybe my system's down in capacity (5-6 tons?) with the low refrigerant, but I can't imagine being cool enough with a couple of roof units. 

I also suggest something that runs off the engine.  I've seen some nice units (Red Dot, I believe) that look like they would fit above the windshield if one has a raised roof.  If not, I'm sure something could be mounted in the spare tire bay and ducted upwards... it would likely be lots quieter than a system mounted in the factory location in the dash or anywhere in the bus itself.  Another possibility would be a mini split, although not meant for vehicles, with the inside section mounted above the windshield or on the side right behind the driver.  A 12,000 btu unit will run off 120 volts.  If your generator is set up for 240 volts, you could use a 18,000 btu model.   I suppose the easiest option, though, would be another roof unit (15,000 btu) mounted close to the front and ducted to right above the driver to cool the area heated by sun on the windshield.  Good luck with it.  Let us know what you decide to do.  Being hot and driving for hours really sucks.

David

[kingfa39]

I made up my own system for my 4106, two 22500 btu evaporators, one in dash one half way back mounted in dinette seat, one condenser and a jap compresser, never run the roof air on the road, no need, these are small sized street rod evaporators but pack a pretty good punch. one of the best things i ever did to my bus
Frank Allen

[Devin & Amy]

kingfa39,
where did you get the stuff? took out my OTR air and have regretted it ever since. except for the genset space I gained.
Devin

[oldmansax]

Assuming the OTR system is gone and the gen set is now where the condenser was. You want to put in a dash air unit. Where do you put the condenser? The former AC lines to the engine compartment are now full of wires. Where do you run the new lines? I have a MC7 BTW. Suggestions?

TOM

[Nick Badame Refrig/ACC]

Assuming the OTR system is gone and the gen set is now where the condenser was. You want to put in a dash air unit. Where do you put the condenser? The former AC lines to the engine compartment are now full of wires. Where do you run the new lines? I have a MC7 BTW. Suggestions?

TOM

Hi Tom,

Behind one or both of your engine radiators is a good spot.

Nick-

[TomC]

I have a 40 x 102 transit with very large single pane windows with a light tint.  I also have 2" of sprayed in insulation in the walls and ceilings (nothing under the floor except my carpet with pad).  Last summer coming through mojave desert, it was 107 degrees and with the two front A/C's running (have three) was a comfortable 76 degrees inside while driving.  I also have a dash fan that blows air in my face that works well.

I think that instead of looking to add more A/C (those two roof tops should freeze you out of a 35 ft'r) you should look into insulating the bus better and look for air leaks going down the road that lets hot air in.  Good Luck, TomC

[rv_safetyman]

I installed a Red Dot 5045 and it is a great unit.  It is rated at 46K BTU heating and 33K cooling.  Think about it, that is more than two roof airs!

It fit very nicely under my new dash.  I have attached a photo that sort of shows the installation.

The unit has a cable controlled flapper that diverts the air flow from the front four fully adjustable outlets to the back opening.  On the back I made a plate with 4 outlets that connect to the defroster outlet hoses. 

I plumbed the heater to my AquaHot and that really makes a really nice setup.  This morning is was a bit cool, so I fired up the Red Dot and had great heat flowing towards the passenger seat where I was sitting.  I can defrost the windows without even starting the engine!  The heat going down the road has been sufficient for any condition we have encountered (have been in Zero degree weather) while going down the road

The AC is absolutely great and can handle most any condition we have encountered except heading west in the late afternoon on a hot day and even then it makes the drive bearable.  My bus is not well insulated and still has some air leaks that I am working on.

Jim

[belfert]

OTR A/C is on the bottom of my "I'll get to it someday" list.  Mostly due to money, but in part because I want to get the engine rock solid first and the interior mostly done.  I still have some fairly minor oil leaks on my Series 60 I need to fix.

On my bus it would be pretty well impossible to place the condenser behind the radiator.  With the cooling issues inherent to most buses would it be a good idea place the condenser in front of the radiator like modern cars?

I've been considering a rooftop condenser like Van Hool, but I don't want the big one like a Van Hool and the ones Red Dot sells are fairly small it seems although I really have no idea how much A/C I really need, especially the driver with the large Dina windshields.