# New to air compressors and acquiring one



## Your82 (Aug 1, 2014)

So my stepfather is gifting me an air compressor that his friend got out of surplus from a hospital. The issue with it is that supposedly a two stage air compressor. The way that it is piped, it doesn't appear that it is a two stage. There are two electric motors. One smaller motor has one piston that is pumping into the tank. While the other motor has two pistons but only one is actually hooked up and pumping directly pumping into the tank, the other piston has nothing hooked up to it. I tried looking up the numbers to see what information I can find but I haven't had any luck on even finding the model online. Is there a way that I can figure out what this other piston is doing and if I can hook it up to use? Below is the numbers that I was able to find off of the machine. I will be picking it up Wednesday to take back home with me. Also I would upload photos of it but I didn't think that the info that I needed would be so hard to find.

Ohio Medical Products
Model: oh-t8-4
Pump1: EL
Pump2: Unknown
Receiver1: 318460
Receiver2:
Motors: 3/4HP 208-60-3


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## OldMasterTech (Jul 25, 2014)

Your82 said:


> So my stepfather is gifting me an air compressor that his friend got out of surplus from a hospital. The issue with it is that supposedly a two stage air compressor. The way that it is piped, it doesn't appear that it is a two stage. There are two electric motors. One smaller motor has one piston that is pumping into the tank. While the other motor has two pistons but only one is actually hooked up and pumping directly pumping into the tank, the other piston has nothing hooked up to it. I tried looking up the numbers to see what information I can find but I haven't had any luck on even finding the model online. Is there a way that I can figure out what this other piston is doing and if I can hook it up to use? Below is the numbers that I was able to find off of the machine. I will be picking it up Wednesday to take back home with me. Also I would upload photos of it but I didn't think that the info that I needed would be so hard to find.
> 
> Ohio Medical Products
> Model: oh-t8-4
> ...


Is this intended for residential use? Your specs indicate it is 3 phase 208 vac - most folks don't have that in their garage - also your specs say 3/4 HP? That may be good for inflating balloons for parties but not much else!


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## Your82 (Aug 1, 2014)

This wasn't intended for residential use. It was from a hospital. The motors on it don't look like the original motors. But I am not sure. It was about to be trashed from a hospital but a friend of a friend pulled it out of surplus with the intention of repairing it. It changed hands and is going to be mine next Wednesday, still damaged... I will see about getting pictures of the whole thing to show you. And like I said, I have no idea. It looks like there are three pistons with two hooked into a larger motor and one into a smaller one.


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## Your82 (Aug 1, 2014)

Here are a couple of links to the stamped plated on the compressor if you can make any sense of them.

https://dl.dropboxusercontent.com/u/3554125/air%20compressor/20140731_201518.jpg
https://dl.dropboxusercontent.com/u/3554125/air%20compressor/20140731_201525.jpg
https://dl.dropboxusercontent.com/u/3554125/air%20compressor/20140731_201533.jpg


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## OldMasterTech (Jul 25, 2014)

With only 3/4 HP you should expect approximately 3 to 4 SCFM of air delivery. This would be very low for general shop use. You could fill tires but not run very many tools efficiently. See this chart Air Tools and Air Consumption for some tool ratings.
You did not comment on the three phase issue, do you have three phase? If not you will have to replace the motor(s). There are other ways to use delta on single but pricey.


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## Your82 (Aug 1, 2014)

What I understand by research a phase three system is were there are three pistons, Piston one compresses air and then leads into piston two, then piston two compresses it more and leads to piston three, piston three finally compresses it a third time and puts it into a tank. If that is the definition of a phase three system then it isn't. There are three pistons on the machine. But only two are hooked up, and they aren't hooked up in the manner of the earlier explanation. Both of the lines lead straight into the tank. My understanding is that the piston that is left out is damaged (something wrong with a seal or the reeds) so it is left just standing there.


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## Your82 (Aug 1, 2014)

Here is a diagram of the air compressor

https://dl.dropboxusercontent.com/u/3554125/air compressor/Air Compressor.jpg


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## OldMasterTech (Jul 25, 2014)

Your82 said:


> What I understand by research a phase three system is were there are three pistons, Piston one compresses air and then leads into piston two, then piston two compresses it more and leads to piston three, piston three finally compresses it a third time and puts it into a tank. If that is the definition of a phase three system then it isn't. There are three pistons on the machine. But only two are hooked up, and they aren't hooked up in the manner of the earlier explanation. Both of the lines lead straight into the tank. My understanding is that the piston that is left out is damaged (something wrong with a seal or the reeds) so it is left just standing there.


3 phase refers to the electrical supply requirements of the machine/motors. The building you intend to use this unit in would have to have a 3 phase electrical service - very rare in homes.

The mechanical sequencing of compressing air as you describe is referred to as 2 stage in most common configurations.


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