Drivers A/C & Heat

[Doug1968]

Fellows,

I would like some feedback regarding mounting a heat & A/C system out of late model motor coach into spare tire area of my MCI 102a3.

The unit is about 20" square and also about 20" tall. Would have the factory wire loom and dash controls but I would have to build new ducting to fit my application. This unit came out of a diesel pusher so I assume it would be adequate for the drivers area of my coach.

The compressor is a Sanden Model 4641. Some questions I have are:

1) I assume the compressor can be engine mounted at the rear and still handle the requirements?
2) I would have to make new freon lines to run from front to back. Any issues or anything special required for this?

Any recommendations or comments would be appreciated.

Thanks,

Doug

[luvrbus]

Doug, call Sonnie @ 903-815-2141 he will tell you where to install the oil loops on that unit to keep from having compressor problems and anything else you need to know about the install of the unit.
If that unit is a Pro/Air 963 I have books for it I'll send you 

good luck

[Boomer]

Hi Doug.  I forget if you are taking out your 05G compressor, but the copper OEM lines running forward from that will be too big.  You need #6 and #8 Aeroquip or equivilant for the Sanden so will have to pull them all the way forward.  If you can find a bracket it can be driven from the cam pulley.  Should be fine to put the condenser in there with the discharge blowing down through the floor.  Best to have cool air feed it, but I couldn't bring any into mine, did not want to cut a hole in the siding, so it just picks up ambiant air in the tire compartment and works just fine.  Are you using the evaporator/heater from the wrecked motorhome also?  Don't forget to make a way for the condensation to drain out.

[Boomer]

Doug I have diagrams for the system or if you want to check out mine, come on over anytime.

[JohnEd]

Doug,

Why aren't you using the drivers air/heat system that came with the bus?  Something inherently wrong with that system?

Boomer,

Why would he have to reduce the size of the lines?  Thanks.

John

[Doug1968]

John,

I would like to keep the factory a/c but those I have talked to say the upkeep is expensive?

Mark,

What do you think about mounting the a/c unit in the current a/c bay? There is more room than under the driver and it already has the vented door for air flow? It would require longer ducting to get to the dash?

Clifford,

I'm not sure of the manufacturer or model number. I will let you know and I will talk to Sonny if I go this direction.


Doug

[JohnEd]

Doug,

The OTR Prevost AC uses a compressor that would handle a office building.  It was sized to chill a bus that had been sitting in 120 degree Az. sun "as the 50 passengers" were boarding.  OVERKILL!

It cost a lot to operate that system even if it is trying to conquer only 85 degrees and the heat generated by two souls on board.  The compressor, condenser and passenger evaps are just to large to realistically consider.  Maint and upkeep are truly expensive and beyond our ability to support.  BUT......that evap unit up front that services the driver and the extreme front of the bus is ducted, fan equipped, thermo controlled and maintainable with parts from Pre or used or commercial.  If you hook up a freon source and hot water you have a canned system that will cost you practically nothing to "install".  The freon comes from a auto sized compressor that is driven by the engine, just as the original system was but with greater efficiency.  Add a evap in the rear and you cool the entire coach....but with a much much smaller compressor.  There are more details but they are just that.....details.

Good luck with your project,


John

[Doug1968]

John,

I would like to look into your idea. So to do this would it be a matter of replacing the compressor (with a smaller unit) and running new lines to from the compressor to the front? You mention adding a back unit and water?

What do I use for the large condensor that I tear out? Do I add a small condensor?

Doug

[JohnEd]

Doug,

I have heard form Nick no less, that "all" the components in an AC system must be sized correctly.  That is the party line as I understand it.  That would mean that the compressor neds to be at least of an adequate size and that is your primary limiting factor as far as cooling capacity band, I think, a starting point.  The capacity of the common auto ac is a couple tons but that is just my spit ball.  They do make them in much larger sizes and I think that is what you want.  Problem is I don't know what that size is but the bright side is I am not selling my expertise.  Here is what I do know....the size you need for a Pre is, in fact, known and this has been done many times before.

Get a reading on the size compressor you need.  Consult an AC shop for what car an AC compressor meeting that spec is standard equip on.  Shop the wrecking yards for the compressor.  Make sure it is known to be reliable, efficient and very common...read cheap.

Your AC shop can sell you a condenser that is sized for your standard equip evap unit in the front.  You might consider installing the condenser at the front of the coach to take advantage of ram air but I would rather use the engine radiator location to take advantage of that fan.

Recently I read that the "lines" running to the front of the bus were too big to operate only a drivers air evap.  I have never had it explained how a condenser or the lines associated with it can be TOO big but a lot confuses me.  That I should understand, though.

If you use the stock sys lines you should be able to get by with installing new lines in the engine compartment only.  You do have to cap off the passenger system and the stock condenser.

There are air handler/ evap systems sold that are compact and very powerful.  They are used in trucking and ambulances and all sorts of aps.  I think Red Dot is one mfr but there are more than a few.  Look at what they have to offer and the options such as heat and remote thermo and multiple speed fans, etc.

Your drivers heat and defroster system should be the best you could want.  Keep that by capping off the passenger system and maybe install a rear heat exchanger.

I have no numbers for you.  They are often peculiar to your individual situation anyway.

Good luck,


John

[Dreamscape]

There must be a calculator out there somewhere to determine how to size it. Anybody have any ideas on who might have one?

I'm A/C illiterate and would like to learn the proper procedure.

[Boomer]

Doug, I'll explain and give you some diagrams when you come over Thurs.  Thanks

[JohnEd]

Paul,

I don't think calc will work.  Too many variables.  I have never seen a pre with more than 4 roof top units and I can assume that they are 1,500 BTU units.  That would be 6000 BTU for the entire bus.  Many have installed a single one ton unit for the drivers area and they seem happy even though I think that is not sufficient.  It doesn't matter how much larger the compressor is in terms of BTU as the front evap is also rated and that is the governing factor.  Were you to install the compressor from a mini van that would be more than enuf for the drivers air without doubt.  If he wants to install OTR for the coach he could simply add a second compressor for that part.  An AC shop could most likely provide guidance for using one large auto unit and two evaps and I think that would be the most efficient.

I don't think you can size the components by "figure'n".  It has all been done before, though....like how many rooftops.  But then I did make it clear I am ignorant....right?


Wonder why no one has chimed in with the answer for the guy?


John

[luvrbus]

How does 60,000 btu sound to you John 6000 is a little on low side 

good luck

[JohnEd]

Clifford,


Well is my face red...... OR WHAT?

I keep doing that, dang it.

Thanks for the correction that might have led others to a mistake.  Heck, I reread my own posts and that mistake might have led my own self to screw up on my own typo..  Hope thats clear. LOL

Thanks,


John

[robertglines1]

Doug : think you got your answer rite off. I'm doing same thing. My drivers air compressor was missing on the on the salvage shell I am rebuilding. The engine I purchased out of a freightlinner came with the ac compressor very close to the same size as the original drivers AC compressor from prevost. (I have one on my 89) to compare to. I was told the equivalent Btu out put would be in the 24,000 range.  Just general info. Just need to add about 6oz extra oil for the line length of tubing/line length.  FWIW   Bob