# 12v single shaft motor to run A/C by belt?



## Trinten (Sep 12, 2011)

So I've been doing some more googling - I'm actually a little surprised at how many "complete 12v DC A/C systems" there are out there, and how tough it is to just get the compressor by itself!

I figured if the torque question couldn't be answered, then I'd go back to trying to find a 12v DC compressor. 

It seems that MasterFlux has a questionable reputation? Some of the posts on the boards here have shown a mediocre feeling about them, at best. 

I did find this unit - http://www.made-in-china.com/showro...or-for-Vehicle-Air-Conditioner-XB135Z12-.html 

Trying to find someplace that sells in it in single units. Some other searching turned up that it uses 20 amps, which isn't too bad. This would fit the bill for my small-cabin car... assuming I don't need to worry about it burning itself out if it doesn't have some sort of electric cut-off in place of a clutch to disengage.

If anyone has any other compressor suggestions like that one, I'd really appreciate it!


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## mizlplix (May 1, 2011)

A common GM A6 compressor operating at it's max. Head pressure needs around 7 hp.

Having said that, there is only one reason to do a belt drive...space restrictions.

When you direct drive an AC compressor, you can cycle the motor to control your refrigerant supply. There is no need to just leave it run and burn up anything. 

Literally any compressor compatible with your chosen refrigerant will work fine. You need the compatible oil and o rings too.

As for motor....look no farther than a Grainger catalog. I would use a permanent magnet motor of the same voltage as your traction pack.

The one biggest trick to automotive AC success is to pull the system down to 500 microns before charging, to assure that all moisture is gone from the 
system. Any moisture at all left innit will cause a higher than normal head pressure and nothing but heartaches.


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## Trinten (Sep 12, 2011)

Thanks Mizlplix!

Can I ask where you were able to find that HP info? The Compressor I have is a GM HR6, maybe the same resource would know what requirements to drive that one would be as well!

I have a couple questions on the direct drive setup, instead of belt:

In a direct drive setup, to cycle the motor, I was thinking that it could be done by rigging up whatever tells the clutch to engage/disengage to tell the motor to kick on/off. I would think that would be more "fool proof" than remembering to cut the controls from A/C to vent and back every few minutes? Is this even possible?

Are you also implying that as long as the motor driving the compressor has the appropriate HP output and able to turn the compressor at about 1300 RPM, then I don't need to worry about the torque of the motor? 

My space constraints aren't too bad width wise or depth, length wise it's a bit tougher, that's why I was originally planning on putting the two motors side by side and using a belt - but I could put them nose-to-nose for a direct drive setup. 

Thanks again for the help and info!


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## mizlplix (May 1, 2011)

My "resource" was a GM salesman. He was defending that units use in school buses where they were failing every 90 days or so. It turned out that the condensers were sized 30% too small, not the compressors fault...

I have 35+ years experience with mobile AC systems in fleet environments. Literally everything from a pick up truck cab to a 84 passenger pusher transit bus. 

AC systems are actually basic. You attract heat into a medium, move it to another location and remove it. The AC must simply remove heat slightly faster than the cabin let's it leak in......

They need only to be as complicated as you want them to be. From a single zone to a multiple- layered climate control system. 

When guessing hp requirements of a given compressor, look no farther than the belt. What is the belt good for? The comp will be less than that.


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## Trinten (Sep 12, 2011)

Thanks again!

Any opinion on how to cycle the motor in a direct drive setup? 

The belt tip is a great one, I've always just bought belts by needed width and length, never even considered their rating.


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## piotrsko (Dec 9, 2007)

unless your system is a home build/ kludge style, it will have a control for the compressor clutch. use that wire through a relay for the motor powering the set up. switch is usually the temp control one.

84 passenger bus? odd number that unless you have full rear seat with 6 across. I've done 96, but 1 st graders only, 46 pass with high schoolers.


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## mizlplix (May 1, 2011)

Yes they are a pusher and have a continous rear seat, (unless you have an International with the DT466. It is so long it sticks into the rear seat area and cuts out 2 center seats.)

With the good Trans-Air AC systems, they run in the $120,000.00 range.

The bus seat rating is set by a 13" wide rump. To get full loads they have to be very friendly first graders...LOL

If you ever get to Vegas, check out the Clark County bus yard. They have a slew of them. Almost more than the entire state of Arizona put togather,

MIZ


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## piotrsko (Dec 9, 2007)

mizlplix said:


> The bus seat rating is set by a 13" wide rump. To get full loads they have to be very friendly first graders...LOL
> 
> If you ever get to Vegas, check out the Clark County bus yard. They have a slew of them. Almost more than the entire state of Arizona put togather,
> 
> MIZ


way off topic here, BUT our new busses are 102" wide, so the seats are even wider as is the aisle way. wouldn't think 6" makes that much difference.

Yeah, their yard is bigger than my school district.

We now return you to our regularily scheduled topic.......


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