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Author Topic: Over The Road Air Conditioning  (Read 4369 times)
Fredward
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« on: February 02, 2008, 09:00:16 AM »

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
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Nick Badame Refrig/ACC
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« Reply #1 on: February 02, 2008, 09:07:44 AM »

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-
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cody
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« Reply #2 on: February 02, 2008, 09:55:00 AM »

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?
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« Reply #3 on: February 02, 2008, 10:38:08 AM »

I open the windows, but watch the paper towels.

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« Reply #4 on: February 02, 2008, 11:04:49 AM »

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?
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« Reply #5 on: February 02, 2008, 11:19:21 AM »

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-
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chris4905
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« Reply #6 on: February 02, 2008, 11:23:48 AM »

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.
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Chris & Cheryl Christensen
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« Reply #7 on: February 02, 2008, 12:23:00 PM »

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
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kingfa39
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« Reply #8 on: February 02, 2008, 12:40:37 PM »

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
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« Reply #9 on: February 02, 2008, 01:47:39 PM »

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
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« Reply #10 on: February 02, 2008, 02:03:02 PM »

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
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« Reply #11 on: February 02, 2008, 04:39:50 PM »

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-
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« Reply #12 on: February 03, 2008, 12:35:34 AM »

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
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« Reply #13 on: February 03, 2008, 06:53:12 AM »

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
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« Reply #14 on: February 03, 2008, 08:02:16 AM »

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.
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« Reply #15 on: February 03, 2008, 11:22:37 AM »

The nice thing about Red Dot is the many different configurations you can get.  With the marginal cooling on most buses, I would highly recommend using a remote mounted condenser with a built in 12v fan.  Personally I would think there would be enough unused space up front near or under the drivers seat that the condenser could be mounted there. Then all that would be added to the engine would be the belt driven compressor.  Red Dot makes the A/C systems for Freightliner, Peterbilt, Kenworth and others-so they are both tested and reliable.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #16 on: February 03, 2008, 02:05:13 PM »

I think air infiltration is the real FIRST ISSUE.  Insulate all you want and get as big an air conditioner unit as you wish, but leave a window open and you are going to be at ambient.  The frontal area of the bus has to be hermetically sealed and all the front has to be air tight cause that is a high pressure area and you let a really efficient flow of air into the bus with a comparitivly smallish hole up there.

Just sitting with the heat on I'll bet it is easy to keep toasty warm....even with holes in the front,  so that isn't proof of good sealing.


Good hunting.

John
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« Reply #17 on: February 03, 2008, 05:01:51 PM »

Fredward,
      You have way to many air leaks causing huge heat gain while driving. Things like door seals, window seals, unplugged old ducts etc.   I use a single 18,000 BTU/h ductless minisplit and can maintain 72 inside while driving 65mph on a sunny 95 degree day.  On a similar day parked in the sun it was 70 in the bus.
Your results are about what I was getting with 2 'portable' heat pumps rated at 10, 000 BTU/h.  The portables were simply fraudulently rated and really weren't delivering even 5,000 BTU/h . 
Regards
Jerry 4107 1120 

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Fredward
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« Reply #18 on: February 03, 2008, 06:52:26 PM »

Jerry,
I think that is my problem. The RV windows are cheap and they rattle when I drive which means they must leak. I don't know that I have any major leaks in the front, but obviously there is a lot of hot air coming in somewhere. I've considered replacing the new windows with higher quality new windows. I still like the idea of putting a Red Dot or similar supplemental AC because then i wouldn't need to run the generator as much. We have a 2K inverter which will handle anything else necessary while driving down the road.
Fred
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Fred Thomson
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« Reply #19 on: February 03, 2008, 09:38:19 PM »

Fred- the power to run the A/C has to come from somewhere-whether it be running the generator, having a belt driven compressor on the engine, or extra drag on the engine alternator running the A/C through the inverter.  Personally, just stay with the roof tops running the generator (it's what I have and like it) then you won't have the extra A/C system to contend with and the 35 ft of freon lines from the engine to the front of the bus.
Whether it be a 5hp draw on the big engine, 5hp draw to run two roof top airs, the amount of fuel burned is nearly the same to create the needed power for the air conditioning no matter what's powering it. Good Luck, TomC
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« Reply #20 on: February 03, 2008, 10:30:19 PM »

So how much do these Red Dot units cost on average?

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« Reply #21 on: February 03, 2008, 11:52:50 PM »

In my opinion, a separate engine driven bus A/C is the first class way to go.  If I bought a coach that had it, I would attempt to keep it going.  That is one reason I have considered a Wanderlodge in the past.  That stated, since the coach I have does not have one, I would stick with the roof airs.  For the front unit to really work for the driver, it would have to be as far forward as possible although I have seen a rooftop unit ducted to the front.  I suppose this could even be a for-the-road-only removable duct or some sort of booster fan could be included to get the air where you need it.  Our first regular motorhome had dash air but, since we lived in the desert, we found it best to curtain off the front of the cabin anyway.  Unless one has unlimited resources, it's always a matter of prioritizing time and money.  A new dash air system would not be at the top of my list.
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« Reply #22 on: February 04, 2008, 04:40:43 AM »

If I were to buy another bus, I would give serious thought to keeping the over the road air and heat. That said, the system I have in my RTS is very comfortable. There are two Carrier 13,500 btu ducted roof airs with ceiling vents located where we need them. there are four vents up front that keep it cool. Last summer we drove for several hours with an oat of 98* with the sun comming in my side window, and it was still very comfy with the air on low speed.On High it freezes us out. Granted I have a lot less interior volume than a lot of you, but a properly designed roof air system will work fine, provided there is good insulation.  Donn
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makemineatwostroke
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« Reply #23 on: February 04, 2008, 07:32:06 AM »

Guys, if its so easy to cool these buses with 1 or 2 units why does it take 5 or 6 units with over the road air to keep the converted Prevosts cool that are foamed at the factory.     just asking
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« Reply #24 on: February 04, 2008, 07:41:02 AM »

Maybe size or glass area.  I have 3 rooftop airs and I like to be cool.  When my over the road air developed problems on a trip last year, the rooftops didn't come close to keeping me as cold as I like.
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« Reply #25 on: February 04, 2008, 08:37:11 AM »

I also like to be cool ... some would call it cold... when I drive.  The 76° mentioned in an earlier post, although at very extreme outside temps, wouldn't be cool enough for me.  Our humidity sucks, too.  I'd like it closer to 70°.   The heat radiating off the windshield and driver's window is also pretty intense.  I'm thinking that some of the factory 'conversions' have so many units (5) is because they're often painted black or some other dark color on the roof and that it takes 3 units to keep it cool throughout the bus normally, 4 to cool the back area, and the fifth one for when one's trying to cool the bus down initially or if one of the other units fails.

David
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luvrbus
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« Reply #26 on: February 04, 2008, 09:43:50 AM »

Last year I purchased a Red Dot system like Jim has with a remote mount condenser I haven't installed it yet because of all the work so I am thinking about selling it and going with the 110 unit from Proair or Dan Hard that way the inverter or generator ( if I need the crusie air to help) can supply the power on the road or I can use a power pole at RV camp ground.I know it won't have the BTU as the Red Dot but I won't have the 40 ft of hose and freon to worry about
« Last Edit: February 04, 2008, 09:49:02 AM by luvrbus » Logged
steamguy56
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« Reply #27 on: February 04, 2008, 09:49:17 AM »

Removing the o/t/r for space in this area, the bus was equiped with helper system in the back, this removed. I would like to use it up front.
                         Danny
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« Reply #28 on: February 04, 2008, 04:36:14 PM »

What could one sell a complete working OTR air system for? (102a3)  I think this would have alot to do with whether one would keep in it and deal with the extra maintnence or look elsewhere...
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« Reply #29 on: February 04, 2008, 05:10:42 PM »

Many years ago, I sold a good compressor and condenser for $1000.00 and I don't expect their value has gone down. Those are the two components that get frequent replacement, while the rest of the components probably have not much resale value. Give them to the buyer of the compressor and condenser as a bonus if he gives you a good price.
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« Reply #30 on: February 04, 2008, 05:47:39 PM »

Stan, did you sell those to me in Peterborough, back a number of years?

Big factory conversions have 5 roof airs, because at that price point, I'm not waiting for the coach to cool down if it has been parked in the sun. There is NO EXCUSE for the AC to ever not cool the coach in a noticeable way. No waiting. Excess capacity is part of the price of entry.
Bragging rights to make up for hidden inadequacies might play a part as well...

Riches have their rewards, and their expectations...

In commercial use, think band/entertainer/VIP bus,  if there is a failure in a unit, there is redundancy and the coach can continue until it gets the time or to a location convenient for service (or is just left for the next user/owner by the less reputable leasers)

I was told, can't remember the source or the validity, that openings the equivalent of a 4 inch round hole would defeat our busnut efforts at AC, due to the air infiltration issue. Easily that kind of opportunity at the front of the coach, pedals through the floor, defroster, suction around the door is massive, through the electric panels beside the driver, the gap around the old door opening pushbutton on the front, the old air intakes on the sides, and out around every window seal, slider, crack and crevice.

Lots of places blow in by pressure, lots of places suck out by vacuum, due to the coach punching through the air.

Another reason the stock system was sized so large? infiltration, pull down and 39/41/43/47/55/56/57 people all living, breathing and sweating inside. Oh and the driver.... A busnut has only removed the large number of people, the rest of the loads remain.

happy coaching!
buswarrior
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« Reply #31 on: February 04, 2008, 07:15:25 PM »

I have gotten Red Dot units out of a 15 year old school bus for free because those in Florida convert them into “goat” units for orange pickers. You could look up salvage yard for roll-over or badly front end damage or coach body already removed from chassis. It is a large unit that sets next to driver and another heater unit near above the rear dual wheel. School buses are very hard to cool & heat due to thin wall or no insulation and never ending infiltration….in other words their heating & cooling are bigger to accommodate the coach design.

I would be sure all leaks are stopped before changing to larger unit.
You can find leak the easy way by temporary attaching a discarded furnace blower on top of overhead vent or escape hole. Close all vents & heater air valves, then pail of warm water with ¼ cup of dish washing soap. Take a sponge mop with handle and apply the soapy water over joints (seal, metal, and fiberglass) and look for bubbles. You can use portable hand-pump pressure tank to wet-spray over what mop can’t do. You will be surprised how many leaks you find.

FWIW

Sojourn for Christ, Jerry
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« Reply #32 on: February 08, 2008, 10:47:17 AM »

I noticed in this posting that several have mentioned putting equipment in the spare tire compartment.  Does that mean that you are running without spare tires?  If so, what is the logic, and if not, where do you put the tires?  Thanks
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« Reply #33 on: February 08, 2008, 11:02:00 AM »

Lin,
There was a poll on spares; you can see the results and comments at

http://www.busconversions.com/bbs/index.php?topic=7148.0
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