Compressor Question?

No.
Yes.
You probably have a leaky pipe fitting at the pressure switch.
- Michael

Yes, compressors are supposed to hold air indefinitely. When my tank goes empty I find that I left something plugged in.
Richard
JB wrote:

I have the same problem, leaking at the relief valve or motor control valve.
i

My tank is always at 135 PSI, unless like the last poster I have left something plugged in! My IR tank go goes for days not being used and maintain the 135 PSI/...
Searcher1

It should not leak. That said it is often difficult to stop ALL the leaks. I have a small portable compressor that will hold air indefinitely. I sometimes will not use it for a year and it will be up to full pressure yet. My 60 gallon in the shop does have a small leak in a tank fitting. It will leak down enough to run about every three days. Not enough that I am worrying about it. If you have a leak that dumps the tank in a day it should be easy to find! Greg

It's not really normal, and it's a waste of electricity. With an 80-gallon tank, it should hold well enough to not need to cycle for several days. Your old pressure switch may well have a small leak - but there is one other much more likely place the leak is...
Does the pressure switch have a small air line (nylon or metal tubing) going from the pressure switch back to the big machined brass fitting where the compressor output goes into the tank? If it does, you have an unloader valve on the pressure switch, and the main check valve going into the tank (inside that machined brass housing) is leaking air back out of the tank.
The unloader is literally using a Schraeder tire stem core as a valve, with the stem being valved by a little arm off the pressure switch mechanism. They're so simple as to be darned near foolproof - it's the check valve that goes bad. The unloader is supposed to hiss for a few seconds on each shutdown to relieve the air in the compressor output line, then stop.
AFTER venting the air tank to zero and locking out the power for safety, pop out the tank check valve and stop by your local industrial supply. They're a common item, IIRC under $10.
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Bruce,
Thanks for yhe response. You hit the nail on the head, I am going to try and find a replacement check valve. Does MSC or Grainger carry them? Is the check valve part of the pressure switch?
Thanks again.
Joe...

Gee, lemme go look now that you... Grainger has the plain-jane versions with 1/2" or 3/4" F NPT ports at each end, and an 1/8" F NPT unloader port. #395 Page 1388 - 1/2" 4x828 $15.00 3/4" 4x829 $22.40
These are described as "all-brass bodies with filled Teflon poppets..." so I'm not surprised they start leaking early. I wonder if there's a 'premium' version out there with a gasketed seat...
Feel free to go hunt around at MSC - I don't have a paper catalog.
I've seen them with several other factory configurations machined onto each end. The most common have been Male NPT on the storage tank end, a compression tubing fitting on the Compressor end, and a push-on 1/4" OD nylon tubing fitting to the pressure switch unloader.
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Bruce,
My Sincerest thanks.
Joe...

yes it was rather helpful and encouraging ..............

also inspired me to take a new look at my compressor's air leaks. I used not to worry about them, but now feel that it is not adequate. Thanks Bruce and others.
i

You're welcome. I try to make people's lives easier where I can - I've walked in to fix their lights, and ended up picking up two or three little totally unrelated things like that leaking check valve at the same time. You have SIX senses, use them. ;-)
Like using the "one finger check" to see whether the AC is low on Freon - if the big line is getting cold or not after the system's been running for a few minutes...
If the AC system is critically low on refrigerant, it'll put out cold air for you but the suction line at the condensing unit won't get cold. Meaning that it's going to finally quit working in a few days or weeks, depending on the size of the leaks in the system. And that excess cold is how the hermetic compressor motor gets it's cooling, so running it that low is not a good thing.
And buildings where the hydraulic elevator control valve leaks down just a little bit when the car isn't being used, that one just bugs the heck outta me. You're in there on a ladder changing a light ballast, the car goes 'bump' and drops down an inch, and my "internal earthquake alarm" goes off...
Equipment does odd shit like that for a reason. Figuring out the how and why is most of the battle, after you have that nailed the fixing is the easy part.
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PS. Sight, Hearing, Smell, Touch, Taste, Common. The last one's rare.

A customer called me Wed morning to come check out an air compressor. A brand new..well..several weeks old I-R piston type compressor. When they turned it on via the master disconnect at the inside subpanel..it blew the breaker. The compressor is located outside their shop inside of a chain link fence with privacy slats on it.
Sometime during the previous evening..parties unknown tried to steal it. Unfortunately..I suspect they were not english speakers, or anyon with a firm grasp of tools, engineering or the slightest amount of common sense.
Somewhere during the theft...after trying to move it intact..they tried to take it apart. Not having the proper tools, they resorted to a sledge hammer.
I gave them a quote for labor plus materials to put it back to right. Which will be mostly spending the day removing or cutting away the running gear and bolting up new assemblies.
Ill post pictures next week. They will not be pretty.
I rather wish that the company had forgotten to turn off the compressors power. When they gummed away at the primary wiring with a small pair of some sort of plyers...they would have received their just rewards. 460vt, 15hp motor. Big breaker...
Gunner
"At the core of liberalism is the spoiled child - miserable, as all spoiled children are, unsatisfied, demanding, ill-disciplined, despotic and useless. Liberalism is a philosphy of sniveling brats." -- P.J. O'Rourke