Ideal A/C compressor RPM

[Xephius]

Hey,

Does anyone know the ideal RPM for the A/C compressor equipped in our vans?

The reason I ask is.... I am thinking of building a Tramper (but cooler), and using the installed rear A/C in the van back. So then it would be just a matter of mounting an evaporator and fan under the van body, then connecting an AC/DC motor to the compressor. All easy to do. I just don't want to hang a window unit or a roof mount RV style system on it. I must maintain my low profile and aerodynamic advantage so as to out run other "Tramper" haulers...

-X
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[LiftedAWDAstro]

Well, you can figure the engine normally spins at what 1500 - 2000 rpm's and has a 7" crank pulley. The a/c pulley is about 4.5" to 5" so it would be spinning around 30 - 35% faster.

[Xephius]

Yea, I thought of looking at the belt system on a stock Astro, but I don't have one to look at! I was hoping someone out there may know, or be able to go look. ;)

Thanks, that gives me a place to start. I will need to gear up a "standard" A/C motor to hit the ideal. Most A/C motors spin at about 1350RPM on 115 VAC.

Thanks for the heads up.

-X
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[peter]

Actually, most standard start-capacitor-assisted motors spin at 1750. I think you'll prolly need around a 1/2 hp version. May I suggest (seeing as you wanna run the compressor on a 120v motor) that you rig up a nose-to-nose set-up, also known as a direct-drive. Direct drive reduces drive losses which should help if you're using a generator to power this contraption up. Forget about bothering with direct-drive if you're connecting to 120v campground juice.

In theory, I believe that the typical a/c compressor runs at/around 1:1. Running a 1050 rpm motor will consume less in energy at the cost of reduced capacity. But seeing as the a/c of a car is supposed to be sufficient in heavy traffic, the engine's only running at 800 rpm anyways. That's why you'll notice that on excessively hot/humid days, raising the idle slightly while in traffic reduces the air temps coming off the a/c vents.

Good luck and take lotsa pics!

[Xephius]

You are right on the A/C motor, I don't know why I was thinking it was 13XX...

I was hoping to go with direct drive, good to hear they are running about 1:1 to the engine. And a 1/2 hp motor will be easy to come by, and it will be quite. I am not 100% that I will go this route on the design, but it is one worth entertaining. I have had luck with mounting cooling fans under my current van, so mounting an A/C condenser under there where the fuel tank is wouldn't be hard at all.

Thanks again...
-X
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[peter]

Actually, Dean's correct about the pulley set-up being closer to 7" drive & 4-5" driven. But still, with a 1750 rpm you should be good to go.
I might add that you're gonna be needin' lotsa juice to run this thing. Between the compressor, condenser & evap fans, I figure you'll need over 2k watts in juice. Did you intend to run campground power?

[Xephius]

Yea, I will run it off big A/C power, or my jumbo Honda Genny. It has 2 15amp 115VAC breakers and has run everything I have thrown at it yet. But 99% of my power source would be from grid power. But that does bring up that I need to plan on building a small 115AC -> 12V DC power converter.... Or maybe I will just jack one out of an old camper and be done with it....

-X
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