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weirdbeard 02-16-2011 07:23 PM

Big air compressor info...
I was hoping maybe OldRed or somebody else with experience on big compressors could answer some questions for me.

I finally got my dream compressor! $280 for a 10 horse 120gal beast.
I don't know much about these and I have not been able to find much info on this brand. Any help from you guys is always greatly appreciated. :welcome:

Its working fine, but I would like to know a few things.

Its three phase and it does not have any indication of direction.. Does it mater which way it turns?

What kind of oil do you use in these big boys? I would like to change it ASAP.

There is a weird air line going to the crank shaft cover.. What the heck is this? It has a little leak, but I am very curious of this anyway. :confused:

Here are some pictures.. Of the air line and crank cover. Also one of the compressor in the back of my buddys S-10. I love that one! :D
Thanks for any info you can give fellas. :) 02-16-2011 08:42 PM

Compressor pump will only run one direction. Look at the large pulley on pump. The legs form a fan and must direct air over the pump while running.

The odd looking tube has a valve in the compressor end that equalizes the head pressure when pump stops. This keeps the pump from trying to start against full tank pressure.

weirdbeard 02-16-2011 09:14 PM

Thats a good idea.. I will just make sure the fan is blowing the right direction.

It still does not make sense to me why that little cover would need to be connected directly to the tank. :confused:

NEW INTERIORS 02-16-2011 09:40 PM


Originally Posted by

The odd looking tube has a valve in the compressor end that equalizes the head pressure when pump stops. This keeps the pump from trying to start against full tank pressure.

Yes... your right about the little line bleeding off the head pressure, But they are not usually tied in at the crank case.. :confused:

930dreamer 02-17-2011 03:59 AM

There should be an arrow on the pump pulley that shows rotation.

cal1320 02-17-2011 05:49 AM

Pulley on compressor should blow air towards the compressor jugs to provide cooling. To reverse rotation on 3 phase you need to swap any 2 of the 3 hot leads that feed the motor. This can be done at the disconnect or breaker box. Please make sure you have turned off the power and check for voltage with a tester before you work on electricity.

weirdbeard 02-17-2011 04:14 PM

Ok.. It was spinning the wrong direction.. It was working, but it sounds better now.. It does not seem to have hurt anything.. I was looking for an arrow on the pulley, but nothing.. Seems like they would have done that..

I have a guy telling me that the little air line going to that crank cover is disengaging the compressor mechanically until the motor gets up to speed.. I might just open it and see what the deal is for myself..

So do you just run normal compressor oil in these big ones? Or could I use some type of motor oil?

Sure could have used a owners manual with this one.

oldred 02-17-2011 04:35 PM

I think what you will find under that cone shaped cover is a centrifugal unloader control. I am not totally familiar with that particular compressor but it seems to be a normal set-up and as such it would appear that line is plumbed in wrong, the unloader should relieve head pressure instead of disengaging the pump. Is that line directed into the tank or is that fitting on the tank directing the circuit to the pump, is the fitting a one-way valve? You can use compressor oil or 30wt non-detergent oil, whether having the rotation direction wrong would cause a serious problem (except for cooling) would depend on whether or not the pump uses an oil pump or slinger type oiling. Obviously if it has a pump then it would not lube if turned backwards however if that is the case and it ran only a short time then probably little or no damage was done. Those things tend to "splatter" lube a little even if the pump is not working and running one backward a few minutes usually won't hurt anything, not saying it is OK to run one backwards but if it happens accidentally for a short time it usuall is no problem.

weirdbeard 02-17-2011 04:43 PM

Thanks a lot Oldred. :) I was hoping you would chime in. I did only run it for about 30 seconds backwards and it seems fine now.. I was a little worried.

That little air line is going into that brass fitting.. I guess it could be a one way valve.. I am going to check that out.. That little line is thing only thing that looks kind of molested on the compressor..

I have never heard of the brand and I cannot find any info on it.. Its made in Rochester NY and seems to be well built.. I wanted a Quincy, but this one was a steal of a deal I think. :cool:

oldred 02-17-2011 05:21 PM

If you only ran it less than a minute then you can forget about it even happening., I can guarantee it didn't hurt anything. As for that line you need to examine the pump head and see if there is anything that has been plugged off, it might explain where that line goes. More likely it was plumbed into the discharge circuit somewhere between the back-flow valve in the tank and the pump. Can you get a better picture of that line/tank connection? I know you have a clear close up but the fitting is partially obscured at the top by that braided line.

weirdbeard 02-17-2011 05:45 PM

Lets see if these are any better.. I am a bad photo taker person.. :embarrass

I don't see anything plugged off.. Not sure where else it could have gone.
Thanks oldred. :)

oldred 02-17-2011 06:06 PM

Ok, false alarm. I see it now and it is just fine there, in fact that is what I meant when I said it should be plugged into the pump-to-tank circuit. Somehow I got the false impression from those first pics that the line was simply plumbed into the tank by itself and the braided discharge line went to another fitting, going back and looking at the first pics I can't see now where I got such an idea-sorry about that! :spank:

Looks like that thing is going to be a real beast, you did well! :thumbup:

weirdbeard 02-17-2011 06:33 PM

WOO HOO! :sweat: Thanks oldred! I'm gonna change the oil and put her to work. :thumbup:

Silverback 02-22-2011 08:43 PM

That brass fitting in the top of the tank is a check valve, so air can only go into the tank, and the small line is an unloader that connects between the pump and the check valve so it doesn't have to start against the tank pressure. I'm actually surprised that it's necessary, I would expect that the volume between the pump and the check valve is small enough and the pump would leak enough that after a few seconds there wouldn't be significant pressure there...

Along these lines, I've always wondered if there is any way to tell which way the compressor should turn without a pulley on it? I have a big old Kelogg compressor head that I intend to setup at some point but I have no idea what direction it needs to turn.

oldred 02-22-2011 09:09 PM


Originally Posted by Silverback
I have a big old Kelogg compressor head that I intend to setup at some point but I have no idea what direction it needs to turn.

If it has an oil pump, or even by looking at the slinger if that type, or if it has a centrifugal unloader control you can determine direction by looking at those parts and you would know for sure.

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