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Author Topic: OTR Drivers AC  (Read 3793 times)
Kenny
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« on: April 25, 2010, 04:43:46 PM »

Gutted the OTR main AC and heat systems. Have kept the OTR drivers heat which is working perfectly. Have also kept the OTR drivers AC evaporator. This is where my challenge comes in.

Using the OTR drivers evaporator, how would I size an automotive engine driven compressor and  condenser unit?
Is there such a thing as oversizing the compressor and/or condenser?
The condenser would be mounted in the spare tire compartment at the front.
Would use the copper lines from the original OTR AC system to transfer freon back and forth.
Would these lines be to large for just the drivers AC evaporator?
Could I then tie in an electric compressor to run when engine is not running?

Kenny
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« Reply #1 on: April 25, 2010, 06:04:23 PM »

Kenny,

     I had Welch Industries recommended to me, but I haven't done mine yet.  I understand he has the spec for the evaporators for each coach and can engineer a system.  http://www.welchindustries.com/auxacsys.html.

     If you try them, post back and let us all know.

Art

 
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Art & Cheryll Gill
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« Reply #2 on: April 25, 2010, 07:55:18 PM »

I tried that link and it did not work.

WVaNative
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« Reply #3 on: April 25, 2010, 08:29:12 PM »

Try this:

www.welchindustries.com/

I shortened the URL and it seems to have worked.

No dog in the fight, though!   Smiley


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JCorey
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« Reply #4 on: April 25, 2010, 10:48:00 PM »

The idea of using an electric motor to drive the compressor is a bad one. For the stock OEM OTR you need a 30 HP electric and you can imagine the current requirements and the tonnage of the motor.  It just doesn't work out from aMATH standpoint.

While your driver only set up will require much less power I think you will be wasting your time.  I thought this was way simpler than Nick has informed me.  He is the resident expert and you should tr giving him a call PM.

My advice is to get the number and mfr and "what car it came in stock and pick one up at the wrecking yard.  Might carry off the condenser while you are there.  You will need a metal fabricator t put togeher the mountfor the compressor.  I think your main problem is going to be getting the system evacuated.  Maybe a vac pump from HF.  Get the biggest dryer/filter you can connect to the thing.  Start pouring in the 134 while monitoring the gauges.  My methode is to add freon till the bubbles in the sight glass start getting wispy....it starts out being a froth after a couple cans then gets more and more clear and perfectly clear is perfectly way to much freon.  Consider how much you will spend to re run all that tubing and a few extra pints/pounds of 134 starts to look good. But Nick might tell you that the lines are too much volume and?Huh and he knows best.  Get the electric fan off of the vehicle you rape and put that in for the forced air when stopped.  Maybe two of them.  Well I think you have already spent $75 or a little less depending on the wrecking yard and the model you are chasing.  Did you notice that your compressor and condenser are "matched"..   I would mount everything and let a shop charge and evacuate it.

Good luck and send pics.

John

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« Reply #5 on: April 25, 2010, 10:54:06 PM »

If you have the compressor in the rear and the condenser in the front then you will be sending very hot fluid up the center isle floor.  I would cool that before it starts its journey.  Also, engineer in a second evap for the bedroom so when you stop it isn't cooking back there and also to serve the one that is napping while you travel.  Prevos are built like that so don't let anybody tell you it can't be done.

Thermostats....fans....duct....ooooooooh. so much fun!

John
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« Reply #6 on: April 26, 2010, 02:31:32 AM »

Kenny,

I would also be interested in your findings on OTR driver's A/C. I have a MCI 5C with the evap still intact.
My PO installed the froward roof A/C a little far back and it does not cut it driving into the sun.

Thanks and Good Luck,
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« Reply #7 on: April 26, 2010, 05:51:28 AM »

I have a extra prevost aux air system it was mounted on rear wall of bus...is very simple set up...uses a compressor like was found on older fords the square type..also the freightliner motor I just purchased appears to be the same:the motor (60 series) just purchased for latest project was out of freight liner:The aux air conditioner has separate coil mounted on radiator. to clear post the freightlinner motor had a air conditioner compressor attached to it for cab air....
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« Reply #8 on: April 26, 2010, 06:03:48 AM »

So many units from emergency vehicles out there at good prices made by Red Dot, ProAir and others that will work for you without reinventing a unit,ProAir has one that works on 110V when parked and 12V underway I am sure there are others on the market. 



good luck
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Kenny
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« Reply #9 on: April 26, 2010, 06:44:48 AM »

To be sure all understand I'll restate what I'm thinking of doing.
Of all the OTR AC equipment, the only thing I have left in is the drivers evaporator coil, expansion valve, isolation valve and the large copper lines running the length of the bus.
My thoughts are to install a compressor from a donor car or truck and belt drive it from my 6v92.
Install a condenser in the spare tire area again from a donor vehicle including an electric fan.
Use the left over lines from the original OTR system to transfer freon to and from condenser /evaporator.
Will a donor compressor and condenser be large enough for the OTR drivers original evaporator?
Are the original OTR freon lines to large for this application or should they be replaced with smaller lines?
Is the distance from the rear of the bus to the front to far for this idea using an automotive compressor?
Yes I know I could simply buy a Redot unit but donor parts are plentiful and much cheaper.
Dumb idea or possibly feasible?
Kenny
   
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« Reply #10 on: April 26, 2010, 07:03:04 AM »

I would think they would be to large for that distance .mine are reinforced refrigerant hoses about 1 inch OD about 3/8 id The set up I have had a separate compressor mounted to motor for aux air. I plan on using it on new project and am considering two units ,one front and rear with 2 separate  Ford type (automotive )compressors..as far as distance My home ac unit is mounted 30 ft away from cooling unit in furnace but it is insulated and not large id 1/2 inch maybe....need experts on this one..I'm intrested in reply also...Bob
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« Reply #11 on: April 26, 2010, 10:53:32 AM »

Will a donor compressor and condenser be large enough for the OTR drivers original evaporator?

YES!  The consideration was that you would have to choose wisely to get one that would also have the capacity to handle the rear evap.  They size the evaps by "cubic inch displacement".  A car has a 6-8 CI unit and a limo has a 10 but the Jeep uses a 10 incher curiously.  They make bigger but those get scarce and more expensive.

I heard you about using the OEM drivers area evap and ducting.  I am sure Clifford did, as well.  His comment about using a Red Dot/Pro Air pertained to putting a unit in the rear of the bus "also".  Not rethinking the front.  I would take your path for the front myself and I only remember reading a single post about replacing it.

Call an auto AC shop and tell them of your dream. Get their recommendation for a compressor and find out what vehicle(any) came with that unit.  Call a wrecking yard for the unit. 

Now, way back I suggested to Nick that the OEM condenser would male a spiffy unit for exactly the system you are describing.  I like overkill and that unit has a 8 of 10 TON capacity.  Any way...its huge.  Nick said that the OEM unit would not be properly "sized" and that my plan was not advisable.  He didn't say my system would not work but only that..... Here again, someone has been exactly where you want to go and all the questions have been thought thru and answered.  What I, and others, are sharing is what we have learned and nobody thinks that this is all that can be known.  All of us want to know what you decide and want to follow your adventure in the detail you can conveniently provide.  We all luv ya. Grin

John
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« Reply #12 on: April 26, 2010, 01:49:45 PM »

Hello:     first you should determine what you need and what you want to cool. The front glass is probably 95% of the heat gain. With my mci 7 one roof unit was not enough to do the job so I installed a split system utilizing the existing front evap and a new red dot unit installed in the kitchen cabinet.  Check with Mr Welch to see what the front unit is capable of delivering in terms of BTUs. The original may be around a ton or so but that was with R22.  The front evap in my 72 MCI 7 was  only cabable of about 9000 btus after conversion to R134. (to convert change the guts in the expansion valve)   mr Welch has the parts
  SO with that in mind I installed an 18000 btu unit in the kitchen cabinet  with a 3 speed blower for a total of about 27000 btu . You can mount the compressor on top of the blower in the rear and run it off the same pulley.
   The condensor is the problem . To get the maximum benefit you should put it on the roof.  Red dot has a unit that is available for about 700 or so.  you can find cheaper condensors if you figure out where to mount it down low.
   I bought most stuff from Welch industries . THey are nice people to deal with and they will install the whole system for you
     I would expect that you would be in the 2500 dollar range for the parts  and installation is extra.
       The bottom line is that it is possible
     
Regards and happy bussin   mike
 
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Mike Lutestanski   Dunnellon Florida
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« Reply #13 on: April 26, 2010, 02:07:16 PM »

Mike,

Great info!  Now, that "split" system has the compressor on the engine and after the condenser is there just a "Y" to the different evap units?  I was worried about trapping the oil in a loop or turned off evap or somthing.  Did you pay any attention to gravity flow of oil back to the compressor?

Thanks,

John
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The price of apathy towards public affairs is to be ruled by evil men." Plato
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« Reply #14 on: April 26, 2010, 04:36:10 PM »

FYI  the prevost aux air system is 2 ton..that's equal to almost 1 and2/3 of two roof units..so if I have two of these separate systems would that not equal 3 and 1/3 roof top units and cool the coach in 80 degree weather?Huh? I have these units left over from previous projects...Info came from maintenance manual...cooling with 37000 BTu now::: would that not equal 50000BTU??before I plan any farther tell me why not to use them...Tecumseh compressor HGB-1000
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« Reply #15 on: April 26, 2010, 06:35:00 PM »

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.
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« Reply #16 on: April 26, 2010, 09:10:38 PM »

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
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"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
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Kenny
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« Reply #17 on: April 27, 2010, 04:27:33 AM »

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






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« Reply #18 on: April 27, 2010, 05:18:42 AM »

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
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« Reply #19 on: April 27, 2010, 05:38:57 AM »

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..
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« Reply #20 on: April 27, 2010, 05:51:34 AM »

 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
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Kenny
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« Reply #21 on: April 27, 2010, 05:55:48 AM »

John, pictures would be great. Thanks Kenny
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« Reply #22 on: April 27, 2010, 06:31:33 AM »

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
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Mike Lutestanski   Dunnellon Florida
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Kenny
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« Reply #23 on: April 27, 2010, 09:04:14 AM »

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
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« Reply #24 on: April 27, 2010, 09:06:47 AM »

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
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« Reply #25 on: April 27, 2010, 09:41:01 AM »

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
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« Reply #26 on: April 27, 2010, 11:21:06 AM »

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
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« Reply #27 on: April 28, 2010, 12:29:47 AM »

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
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« Reply #28 on: April 28, 2010, 05:24:37 AM »

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.
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« Reply #29 on: April 28, 2010, 03:33:09 PM »

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
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Mike Lutestanski   Dunnellon Florida
  1972 MCI 7
  L10 Cummins  B400R  4.625R
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