OTR Drivers AC

[dougyes]

I saw a stock, from-the -factory MCI J4500 conversion model with a 24v drivers AC mounted in the tire bay. The evaporator is a Carrier but there was no name on the motor or compressor. MCI might be able to help.

[JohnEd]

Robert,

I can't decipher all that.  A ton is 1,200 BTU....right?  The RV stuff is rated in a different manner than the home AC.  It is overly optimistic and false advertising except that there is no actual spec that they must meet or declare.

Come back?

John

[Kenny]

I have this love / hate relationship with this board. Seems anyone of us have an idea that maybe near and dear to our heart. We post it and human nature being what it is, we hope and listen for replies that support our ideas and maybe tend to ignore the replies that don't. Then there are the times that you can't ignore some of the replies because they just make too much sense either technically or from a preference point of view even though they don't support our idea. I love it, but and I hate.

Sorry I just had to get something off my mind. Now back to the threads subject matter.

Probally my biggest factor in making the OTR drivers evaporator functional again is the following:

- All the parts and pieces are there and fully functional - Just need juice to make it work

- Seems the popular opinion is there is never enough AC directly in the drivers area. The large evaporator and ducting was designed for this area, why not make it work.

-Existing drivers heat / cool ducting and air flow path would allow for optimum windshield defrost using dry air through the evaporator and reheating through the heater core. 


So maybe , the challenge should be what's the best ways and means to get juice to and from the existing evaporator either electric or engine driven. How about a roof air mounted in the spare area, gut the evaporator and run the lines to the OTR evaporator?
Kenny

[luvrbus]

Kenny, I get a lot of info on what works for ac from these guys www.ackits.com I know oil is the problem on most long runs of lines


good luck

[robertglines1]

From the prevost maintenance manual.....central air is equal to 9 ton ....optional drivers or air units are 2 ton.....I am cooling a 40 ft prevost now with two 14700 window units and a 10000 portable (in bedroom closet) the window units are built together as a basement unit...much quieter than roof top and more economical...less amp draw for BTU delivered...use regularly in south east and midwest in 90 degree weather..presently run generator to supply elect to them going down road..keeps inside 70 degrees..I have no problem running generator going down road but it has quit on me several times and left me in 90 degree temp with no air....various problems mainly with fuel filters and debries out of tank...just need a back up and have parts on shelf to do it..

[crown]

 go to a salvage yard and pull the whole set up from a wrecked moterhome mine is from a monico that way you will have 40 ft lines
the right size condeser and all parts i can send some pictures if you want  john

[Kenny]

John, pictures would be great. Thanks Kenny

[mikelutestanski]

Hello ;   The question of oil flow is a good one.  I ran the lines under the floor in the walkway and just teed the lines to each evaporator. THe condensor is on the roof near the rear of the bus and the filter dryer is in the motor compartment where the lines come back from the front.   

    FYI  a ton of refrigeration is equal to 12000 btu per hour of heat removal and in terms of horsepower will require between 1.5 and 2.5 hp . 
     Just a few notes on the original system in my 7 which was 6 tons for the passengers and the side drivers window. 1 ton for the front windshields. All this was with R-12 which is/was the most efficient refrigerent known.
   R134 is not as efficient as 12 so when you convert a 12 system to 134 you will lose some cooling effect. In this case the front evap will only do about 9000 btu or 3/4 ton of refrigerent effect instead of the one ton effect which R-12 provided..
  The existing front evaporator will only put out approx 9000 btu converted to 134 refrigerent which is not enough.  By adding an another 18000 btu to the kitchen and closing the doors to the rear I can maintain 78 or so on a real hot day with the sun streaming into the front.  THis system only runs with the engine as the compressor is mounted on the blower box.
FWIW       
Regards  mike

[Kenny]

Mike, so I take it you replaced the original OTR compressor with an automotive type, kept the original drivers OTR evap, added an additional evap in your kitchen and replaced the original OTR condenser? 
Kenny

[TomC]

Round figures, a 15,000btu roof top A/C has a 1hp compressor.  Considering that the front A/C is probably more in the neighborhood of 35,000btu, you'd need a 3-5hp electric motor to power a car type A/C compressor to power it.  The only successful crossover A/C's I've seen is when an APU (auxiliary power unit) is mounted on a big rig that ties into the A/C system of the truck and the compressor is driven by the APU's little Diesel engine (that engine is usually around 10-15hp).  I would suggest using the dash A/C for only going down the road powered by a car type compressor on the engine and running new freon lines to the front of proper size.  If you want A/C when stopped, add a roof top or basement A/C.  Good Luck, TomC

[JohnEd]

Mike,

Thanks.  1,200 was a typo.

Yours seems the ideal system design.  OTR from and engine powered compressor with AC units that can be powered by the genny if the OTR fails.

One of the posters replaced his OE  evap in the front to get much more tonnage and used that evap for the driver and to cool the front.  I guess the options, pros and cons present if we are patient and tolerant.  A lot of people are getting smart on this post and we haven't even heard from them lurkers.  My definition of the ideal system is firming up...may never realize it but I know better what I "want".  I tend to require in-lace spares and  back-up system when I can do it.

Now, what is "that oil problem" and how can it be dealt with?  I  need that info.

John

[robertglines1]

All the experience I have is with the prevost system...a aux air on a passanger coach ;located against rear cap to cool the back of bus .It had the Tecumseh compressor...now have a salvage 45E prevost(98) that I am doing and it has the same system but with the hoses ran to the front..the aux system calls for 14 oz oil and the drivers system calls for 16...both compressors are the HGB-1000...the capacity figures covers the a total refill of oil if you have a new compressor it has 10 0z shipped with it so you would need 4oz additional to lubricate lines in the rear aux system or 6 additional oz for the front drivers air to coat the longer lines.I apologize for quoting the prevost manual but what they have does work.  oil type Castrol SW 68(POE) or Arctic 1 (POE) plus 6 lbs of 134A.....BOB

[JohnEd]

I have converted R22 sys to134 a couple times.  I did not get the old oil out and I didn't evac the system.  I did replace the dryer/filter.  Question:  Having overcharged a few systems with too much oil they seemed to run fine.  Does that extra oil simply pass thru the expansion valve and get back to the compressor?

Thanks,

John

[robertglines1]

the way I understand extra oil is what it takes to maintain 10 oz in compressor..you notice there is even 2 oz more to lubricate the lines for the run to the front evap.

[mikelutestanski]

Kenny:    RIght on.   I removed the original system completely and later decided to use the original drivers evap because I happen to have it.  If I was to do this over I would use 2 of the 17800 btu units . One I would have fit into the dash somehow. BUt I have what I have and it works for me.
    Welch air is a good place for compressors and hoses etc. I bought the red dot stuff on line at various dealers . One was in the midwest hilliard truck air i think.
        ANyway FWIW   good luck and keep cool
    REgards  mike