Air Compressor

[JDNewbie]

Thanks in advance for any help or advice.....

I was given what appears to be a "homemade" air compressor. Homemade in the sense it appears someone took a legitimate tank, an electric motor (.5 hp if I am seeing the tag correctly), various fittings, pressure switch to turn it on and off, a gauge, and what appears to be a compressor from some type of AC unit and put together an air compressor. It worked just fine for awhile (and it appears to be an older piece of equipment, so I assume it worked for quite awhile prior to me), and then it just quit pressurizing the tank beyond about 15-20 psi.

There aren't/weren't any leaks, and I don't question the safety of the tank. The tank hasn't been welded on or anything. It looks like a "factory" tank of some kind, probably for an air compressor. It has a valve on the bottom for draining water. With the stand, the tank is probably about 5 ft tall. The compressor and motor sit on top. The electric motor is still good.

It seems a shame to just scrap the whole thing. If I can replace the pump, I may keep it or give it to my brother. He doesn't run a bunch of air tools or anything (nor do I), so this is mostly for keeping the car tires up and blowing out dirt and dust, etc.

Does anyone have any suggestions/sources for a new air compressor pump (I am assuming the old compressor is the problem) and a guess as to what size I can run with the motor I have? I'm not looking to build an industrial strength air compressor or anything. I just want a working compressor so I don't have to throw this away.

Thanks again....

 

[David G]

If a pressure switch issue, then one thing, but if thermal overloads cutting out then could be more.

You said .5 HP, that is a really small motor.

 

[Bob]

As to the compressor not building pressure, could be as simple as a piece of debris under one of the reed or disk intake or exhaust valves in the cylinder head.

As to the tank, if a proper air tank it should have an ASME rating plate tack welded to it giving approved working and test pressures and likely the year built.

If tank is OK, and pump isn't fixable, Harbor Freight and ebay sellers have reasonably priced compressor "heads".

But, if it REALLY only a half-HP motor it's not gonna run a very big one!

 

[Russ from MN]

A picture would be nice! I have built a few air compressors out of older automotive AC pumps, they work very well, but don't
produce a lot of volume. They will use a little oil over time, but if that is your problem it's too late. A 1/2 hp motor
should run one up over 100 psi, but yours obviously has a problem. If you needed internal parts such as reed valves they
might be hard to find. I have used steel fork truck propane tanks, the place I used to work switched to aluminum. New
compressor pumps are available many places, like HF, but with only a 1/2 hp motor it would have to be pretty small.

 

[DoubleO7]

Does the compressor look like this York?

 

[DoubleO7]

This :

 

[DoubleO7]

 

[Russ from MN]

I have used a couple of those, they work well with smaller motors, and I have used the V-twins out of Chrysler's.

 

[Steve@Advance]

So, does it build to 15-20 PSI and cut off?
Could be the pressure switch is bad or out of adjustment. Could be the motor is overheating and tripping an
internal overload.

Or does it just continuously run and never build pressure?
Could be a bad reed or head gasket leak. Or some type unloader valve, probably built into the pressure
switch, if equipped. A restricted air cleaner, something blocking the air getting in. Loose belt, slipping
pulley.

 

[kcm.MN]

From your description, I'm getting the image of someone trying to build a silent air compressor, which utilizes the compressor from an air conditioner or freezer system. Other than the tank, does the unit look anything like these?:

https://www.youtube.com/watch?v=D3AOy7eq5Wk

https://www.youtube.com/watch?v=K3_omihYp6s

https://www.youtube.com/watch?v=F0rkzVbExmI

 

[JDNewbie]

Thanks everyone. Here are a couple pictures. It does not shut off, so I don't think it is a problem with the cutout switch. It worked fine previously, and then just stopped filling up over about 15-20 PSI according to the gauge. ALSO, I looked harder at the plate on the electric motor and it is quite possibly a 1.5 HP motor. It is in an awkward spot and I just can't quite make it out. Awful big for just 1/2 horse. AND, it has been a while and has since gotten dusty, but I did clean out the "filter" when it first stopped working. The final picture is of the plate on the Compressor (note it references R12, which is why I assumed it was some kind of refrigerator/AC compressor. It was far from "silent" and did take quite a long time to get up to pressure, but it would fill up to 100 psi.

 

[kcm.MN]

As long as the tank is in good condition and/or the pressure never gets too high, then there's little danger from the system. However, you'd probably be better off having the tank checked out for rust, then put an older compressor on there from a unit where the tank rusted out.

I personally don't like dealing with used air compressors. If the tank fails, it's most likely to just form small leaks. However, if the controls fail and it keeps building pressure, you've got a very serious problem on your hands!

 

[Russ from MN]

All compressors should have a pressure relief valve, even homemade ones! They're not that expensive!

 

[Russ from MN]

How many amperes does it draw, according to this nice chart I found a 1/2 hp at 115 volts should draw about 9.8.

http://www.sprecherschuh.com/download/sscdn7500F/index/hp-volts-fla_chart_v206.pdf

 

[Russ from MN]

I've never seen one like that before, it looks like an opposed twin. Try to check for oil, it has to have some oil on it,but
if that's why it quite pumping air it's too late!

 

[JDNewbie]

(quoted from post at 13:01:39 01/22/18) All compressors should have a pressure relief valve, even homemade ones! They're not that expensive!

Thank you! I will double check, but I think it does have one. You can't make it out in the third picture because the copper tubing is obscuring it, but in the second picture on the far left hand side about half way down you can make out what I think is this valve. It is on the same piece of pipe as the gauge and wouldn't really serve a purpose other than a release valve. It looks similar to others I have seen anyway. I'll probably just replace it to be on the safe side!

 

[JDNewbie]

Thanks! I think it has oil in it. I know I put a couple tablespoons in the intake after it quit working just to see if that would fix it. It didn't seem to help, but then I was just guessing as to what type of oil would be correct. I have some air compressor oil and that is what I put in it, but since that is a refrigerant compressor of some kind, it probably wasn't the right stuff. Didn't help anyway.

 

[Russ from MN]

What about the crankcase? Putting oil in the intake probably won't help the crankshaft bearings and rods. When I build them I
put a standpipe on the side of the crankcase with a dipstick in it. and I use 10-40 motor oil. And yes, that looks like a
safety valve in the picture.

 

[Keith-OR]

ya it will, if it is a refrig compressor converted to air compressor. All refrig compressor has oil that is pumped around thur the system.