Used Compressor Purchase - Few Things to Replace and a Few Questions (lot of pics)

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woodworker2000

Christopher
Corporate Member
I just picked this compressor up off of CL and have a few questions. It is a CH 60-gallon, single stage compressor with a 5hp motor. The seller listed it as running but when we tested it, it wouldn't pressurize the tank above 40psi and then quit running after a while. We couldn't get it running again so I bought it "as is" for a reduced price...low enough that I was willing to take a risk on it. I'm not sure if the pressure gauge is working or not. The front glass is broken on the gauge so I will probably replace it. It is also missing the pressure switch cover and switch so the electrical connections are exposed.....another thing to replace. The air filter is also missing so another thing to replace. Any recommendations of a different air filter/silencer than an OEM replacement? You may be able to see in the pics the cord the guy used.....just a piece of 12/2 Romex with the ends stripped off on one end which he stuck into the outlet...another thing to replace. As I was thinking about it cutting off, something in the back of my mind is telling me that he had "plugged" the compressor into a 115v outlet instead of a 230v outlet. Does that make sense? Would the motor run for a short time on a 115v outlet before it overheated and shuts off? I intend to add a proper cord and plug to it and will test it but I'm wondering if it is even possible for it to have run on a 115v circuit. Also, you can see the amount of water I drained out of the tank...nearly 2 quarts. Apparently, the previous owner didn't read the big yellow sticker near the bottom of the tank. The water that came out was a light brown but it wasn't too dark and I didn't see any flakes in the water so I'm hoping the water didn't do too much damage to the tank. What do you guys think?

Looking at the pics, is there anything you can see that needs to be done to the compressor (other than what I already pointed out)? Though not shown, I do have the plastic cover for the pulley. What kind of oil should I use in the compressor? Should there be another tube attached to the pump next to the tube that connects to the tank (unloader tube?)? What about the drain on the bottom? Should I think about replacing that with one that is easier to use? Any advice, suggestions or other observations would be greatly appreciated.



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Phil S

Phil Soper
Staff member
Corporate Member
I hear that VT pump is quite good in a homeowner application and hopefully has survived its last owner. Sounds like that owner did not care very good care of his equipment. I doubt that motor would even run on 115 volts, yet it sounds like it tried and may have been toasted. I am not sure if that pump requires a 5 hp motor, but that motor surely is not 5 hp. It only draws 15 amps, which cannot generate 5 hp, I have a similar compressor with a 3 hp motor that draws 16 amps at 230 and my big sander has a 5 hp motor that draws 23 amps. If, as I suspect, that pump only really requires a 2 1/2 or 3 hp motor, the replacement motor will be cheaper. there are many after market air filters, K&N make some of the best
 

FredP

Fred
Corporate Member
I have a 240V cord you can have. It is made for that application with a molded plug. [new]:icon_thum I will try to get Phil to bring me your sink tomorrow. If you want to take a ride Sunday morning or tomorrow afternoon I will have that and the cord here.
 

ehpoole

Administrator
Ethan
A few thoughts, none of which should be taken as definitive since this is sight unseen for me:


1) Running the motor on 120VAC could indeed prevent the compressor from properly pressurizing. The motor will try to match the proper speed (in the beginning with an empty tank) because it is phase-locked to the same 60Hz, but the extremely low voltage will starve the motor of power. Provided it was run this way for only a short time then it should have done no damage, but long term operation in this manner can overheat and damage the motor windings. That said, are you certain that it was a 120VAC receptacle as a 240VAC/20A receptacle looks very similar?

2) The motor isn't really a 5HP motor but closer to a 3.5-4.0HP (say 3.75HP) motor. Not as overstated as many compressors used to be, but they still play the game of inflated HP numbers on compressors these days.

3) A #12AWG is adequate provided that the length of the cord is kept short. However, if the cord will be more than 5-6ft then you would be better served with a #10AWG cord and a 25-30A receptacle and circuit breaker. A short power cord (if plugged in) is covered by UL code and is more concerned with managing voltage drop than a hardwired Code circuit -- but if you are going to hardwire the compressor then go ahead and wire with #10AWG copper all the way.

4) If the compressor was actually operating on 240VAC (rather than the 120VAC you suspected) then the issue could either be a broken or maladjusted pressure switch OR a sticking/failed check valve. However, from your description, I would also be more suspicious that he was trying to run it off of 120VAC in which case everything is probably fine.

5) Check both the oil level and the quality of the oil before you fire it up for the first time yourself. Don't count on the previous owner having properly maintained his compressor. Use a good quality synthetic oil for your compressor (make sure the oil is rated for compressor use). You should be able to obtain the manual for either your compressor kit or even just the physical compressor assembly online, which should contain recommendations for suitable oil. I know Lowes does sell 1-quart bottles of synthetic compressor oil for their Kobalt and CH compressors which should be more than adequate for your compressor... or if in doubt you can purchase brand-name Ingersol-Rand synthetic oil.

6) For the filter you can use an OEM replacement filter or you may find that your local automotive and/or lawnmower shop may have suitable replacements. Choose a filter with at least as much effective surface area as the OEM replacement, or even more if you wish, just don't opt for less.

Most importantly, please enjoy your new air compressor! Once you are properly outfitted a compressor is a extremely useful addition to any shop.
 

wndopdlr

wally
Senior User
The brown discoloration in the tank/water is oil blow by. The fact that there was not much blow by is good news. Change the oil before operating any more as it is fairly safe to say the previous owner never did. I recommend a synthetic compressor oil available at Northern Tool. Make sure you have the motor wired correctly and adequate amperage to your receptical. The motor may be in "continuous run" mode because the previous owner messed with the preassure switch and that is why the cover is off that switch. Only a correct gauge will tell if you are pumping air or not. I have a similar AC made by IR and it pumps up to 180# very quickly.
 

woodworker2000

Christopher
Corporate Member
I have a 240V cord you can have. It is made for that application with a molded plug. [new]:icon_thum I will try to get Phil to bring me your sink tomorrow. If you want to take a ride Sunday morning or tomorrow afternoon I will have that and the cord here.

Thanks, Fred. If tomorrow afternoon works for you, I can swing by. My daughter has a couple of soccer games in the am but we are supposed to be finished after noon. Will send a PM with my cell #.
 

woodworker2000

Christopher
Corporate Member
Ethan-

Thanks for the reply and suggestions. Below are a few responses and a question or two.

1) Running the motor on 120VAC could indeed prevent the compressor from properly pressurizing. The motor will try to match the proper speed (in the beginning with an empty tank) because it is phase-locked to the same 60Hz, but the extremely low voltage will starve the motor of power. Provided it was run this way for only a short time then it should have done no damage, but long term operation in this manner can overheat and damage the motor windings. That said, are you certain that it was a 120VAC receptacle as a 240VAC/20A receptacle looks very similar?

I don't remember for certain whether it was a 120v or 240v receptacle. I am familiar with the difference between the two but there wasn't a plug on the end of the compressor cord....he was just fitting the stripped Romex ends into the receptacle slots. I just seem to have this nagging feeling that it was a 120v receptacle and that I was thinking at the time it must be able to be wired 120v or 240v. When I got home and started looking at the compressor, I noticed it could only be wired 240v...that's when I started wondering if he was using a 120v receptacle. The compressor only ran for about 2-3 minutes before it stopped working. I don't recall smelling anything electrical when it stopped. When I get the proper plug on it, I'll see what happens.

2) The motor isn't really a 5HP motor but closer to a 3.5-4.0HP (say 3.75HP) motor. Not as overstated as many compressors used to be, but they still play the game of inflated HP numbers on compressors these days. I guess I was just repeating what it said on the motor. I guess it doesn't matter how many times I say it is 5hp.....it never will be. :eek: I wasn't aware of the correlation between amps and hp that you and Phil pointed out but I did think 5hp seemed high when newer compressors of the same size have lower (i.e., more accurate) hp ratings.

3) A #12AWG is adequate provided that the length of the cord is kept short. However, if the cord will be more than 5-6ft then you would be better served with a #10AWG cord and a 25-30A receptacle and circuit breaker. A short power cord (if plugged in) is covered by UL code and is more concerned with managing voltage drop than a hardwired Code circuit -- but if you are going to hardwire the compressor then go ahead and wire with #10AWG copper all the way. I haven't decided exactly where I will place the compressor in my shop yet...assuming I can get it running but for a 15amp motor, wouldn't #12 and a 20-amp receptacle (and breaker) be sufficient? I don't intend to wire a very long cord to the compressor. The main 200A panel (not a sub panel) for my house is in my shop so the maximum run from the panel to the receptacle would be no more than 20 feet.

4) If the compressor was actually operating on 240VAC (rather than the 120VAC you suspected) then the issue could either be a broken or maladjusted pressure switch OR a sticking/failed check valve. However, from your description, I would also be more suspicious that he was trying to run it off of 120VAC in which case everything is probably fine. I will know more once I plug it into a 240v receptacle. If it works, I will likely replace the pressure switch since the compressor doesn't now have an on/off switch and the pressure switch cover is missing (exposing the wiring terminals which makes me a bit uncomfortable).

5) Check both the oil level and the quality of the oil before you fire it up for the first time yourself. Don't count on the previous owner having properly maintained his compressor. Use a good quality synthetic oil for your compressor (make sure the oil is rated for compressor use). You should be able to obtain the manual for either your compressor kit or even just the physical compressor assembly online, which should contain recommendations for suitable oil. I know Lowes does sell 1-quart bottles of synthetic compressor oil for their Kobalt and CH compressors which should be more than adequate for your compressor... or if in doubt you can purchase brand-name Ingersol-Rand synthetic oil. I will replace the oil before I start it up again. I downloaded all of the documents from the CH site that seemed applicable to this compressor.

6) For the filter you can use an OEM replacement filter or you may find that your local automotive and/or lawnmower shop may have suitable replacements. Choose a filter with at least as much effective surface area as the OEM replacement, or even more if you wish, just don't opt for less. Just doing some poking around on Amazon, it looks like Solberg filters are decent quality? I guess I am supposed to consider the SCFM rating on the compressor to get the proper filter size? For this compressor it seems that the Solberg FS-10-050 would be appropriate.

Most importantly, please enjoy your new air compressor! Once you are properly outfitted a compressor is a extremely useful addition to any shop. Thanks. This compressor is way overkill for my needs but I've been wanting a larger compressor to replace my PC "4hp", 2-gallon oil-free compressor which runs a little loud.

 
before I sunk alot of money in it I would make sure that the tank is not going to rust out on you soon or at least figure that into a scenario so you do not get too much money into your project
 

woodworker2000

Christopher
Corporate Member
before I sunk alot of money in it I would make sure that the tank is not going to rust out on you soon or at least figure that into a scenario so you do not get too much money into your project

How do you suggest I make sure it isn't going to rust out? I agree it is a concern but how would I check it and/or prevent it?
 
How do you suggest I make sure it isn't going to rust out? I agree it is a concern but how would I check it and/or prevent it?

I'm not sure maybe someone else will have a better idea how to do that..... my 20 gallon got a pin hole in the tank and thankfuly someone here had a extra tank so I can switch it out but mine sursprised me cause I thought I took desent care of it but it was 20 plus years old
 

DaveD

New User
Dave
Did the motor stop and/or seize up or did the compressor start to seize and the motor just couldn't overcome it?

Also it seems strange to me that the compressor pulley spokes aren't fashioned at a fan blade angle to help cool the compressor. Looks like a aftermarket pulley that was adapted to the compressor.

I'd first try running it without building up tank pressure. Then I'd get a known working gauge in the line and see if it will pressurize in a reasonable amount of time. If it dies, hurry up and unplug it, pop the belt off and see who croaked. The motor or compressor?

I wouldn't worry too much about the tank rusting out considering its a vertical tank. I cut open a vertical 80 gallon tank that had been used in a car dealership. All kinds of sludge and crap in it but the tank and end bells on it looked fine.

As to checking one out you do it hydraulically. I've heard of filling one with water and putting a grease fitting on the tank then pressurizing it with the grease gun the last cubic inch or so. If the tank fails all you get is a small leak for a very short time. I think you pressurize them to 2x the rating on the tank tag. However you would decide to pressurize it you would want to fill it 99.99% with water first. Do not try to pressurize it with just air. That's a big bomb if it fails.

Lastly, I wouldn't discount that a previous owner didn't try to cobble together some suspicious quality parts to get it working and failed. The compressor and motor pulleys don't look stock to me and the air filter missing is suspicious. How and/or why could someone possibly lose that part? Wouldn't put it past someone to put that water in the tank either to make it look like it had been running ok for a long time.
 

woodworker2000

Christopher
Corporate Member
Update: I changed the oil in the compressor and replaced it with Kobalt-brand synthetic oil, blew the dust/dirt out of the motor, changed out the pressure gauge, and thanks to the generosity of FredP who gave me a power cord for the compressor, I was able to wire it up correctly and plug it in safely (no more fitting the stripped ends of Romex wire into the outlet). On changing the oil, there has to be an easier, less messy way to get the oil out than trying to fit a plastic cup under the drain plug on the side of the pump and using 1/2 a roll of paper towels to clean up the oil that doesn't make it into the cup . Any suggestions? A 1"-2" extension tube attached to the drain hole would make it much easier. I don't know why they wouldn't have included such a tube in the design.

The good news: The compressor started right up and pressurized the tank to 115psi in less than 7 minutes. When I released the pressure and it dropped down to about 90psi, the pressure switch kicked back on and re-pressurized the tank. I ran through this cycle (pressurizing, releasing the pressure and having it cycle back on) several times and everything worked correctly. The pump pressurized the tank to 115psi consistently in under 7 minutes each time. I tested the pressure relief switch by pulling on the ring (air was released) but I don't think that tells me that it will work if the tank is over pressurized. Is this a normal cycle time for this type compressor and why does it not pressurize all the way up to 125psi?

The bad news: The motor is making a sound that just doesn't seem right. I don't have a lot of experience with electric motors but I believe it sounds like the motor bearings need to be replaced. Also, I peered inside the tank with an HF digital inspection camera and did find rust in the tank. It isn't a uniform coating of rust on the inside but a lot of patches of what looks like raised, flaky rust. It looks worse in some places than others. It looks like something that could be easily removed with a wire brush if I could fit the brush, my hand and arm inside the 1" hole. :)

My questions:
(1) how difficult is it to replace motor bearings? Is this something I should try to do myself or take it to a motor shop? I'm a little concerned that the pulleys will be difficult to remove (I believe DaveD is correct that the both pulleys are replacements) since there appears to be a fair amount of rust where they attach to the shafts.
(2) should I replace the pressure switch? Even thought it seems to be working fine and I would prefer to avoid the expense, I am a little uncomfortable having 240v terminals exposed and no way to shut off the compressor without unplugging it. You can see the uncovered pressure switch in the photos above.
(3) should I be concerned about the rust in the tank? My web-based research on this leads me to believe that it is not uncommon to have rust in the tank since pressurized air naturally has moisture in it. I've also read that you can fill the tank with a phosphoric acid solution which will "eat" and leave somewhat of a protective coating on the tank. Has anyone ever done this? I don't think it will be practical for me to hydraulically test the tank. After I pressurized it, I did listen around the tank for any leaks and didn't find any. Good enough?

Thanks for your feedback.
 

FredP

Fred
Corporate Member
you can adjust the pressure switch on most compressors to set the start/ stop pressure. I am no expert on this so I will defer to others as to how it is done. rust is common and I don't spend a lot of times worrying about it. as someone mentioned when the time comes the tank will simply develop pin holes and you will need to repair or replace the tank at that time. time of recovery is determined by the CFM rating of the pump and the size of the tank. 60 gallons to 115 PSI in 7 minutes on your average home shop compressor sounds reasonable to me. there should be a tag on it somewhere giving the CFM rating at a certain pressure. usually it will give a rating for 40 PSI and 90 PSI. I doubt you will need anything over 115 PSI in a home shop environment.
 

woodworker2000

Christopher
Corporate Member
Fred-
I was thinking the same thing about 115psi being plenty for my needs. I didn't know the pressure switch could be adjusted but I think I will just leave it alone. Truth be known (don't tell my wife), this compressor is much more than I need for my extremely underused home shop. The compressor is rated at 11.4cfm @ 40psi and 9.0cfm @ 90 psi. I'm sure those ratings assume a tank pressure of 125psi but I think whatever they happen to be at 115psi will be plenty for me. On the rust issue, I am probably overly concerned simply from reading about compressor tank explosions on the web........similar to the discussions about how some people find it perfectly safe to use PVC or Pex for compressed air piping while others are certain it will kill you.

For the record, I don't have any intention of using PVC or Pex for compressed air lines but it won't surprise me to see this thread evolve into a debate on whether using PVC or Pex is safe since I mentioned it. While I'm at it, I might as well as say that SawStop and Festool are overpriced and any dust collector or cyclone that traps anything smaller than 1.0 micron is overkill. :gar-Bi. Think that will get things started???

Seriously, before anything does get started, I am only kidding about PVC, Pex, SawStop, Festool and dust collection.
 
at this point I would just use and enjoy it until the time something does break and then deal with it then..... if you just need to spend momey I would put a envelope on the compressor with $10 in it and every month put $!0 bucks more in so when somethimg goes bad you will already have money set aside to deal with it
 

Woodman2k

Greg Bender
Corporate Member
Chris,
I forgot to mention this but when you drain the pump next time replace the plug with a small ball valve that has female threads on both sides.Now ,put the original plug in the ball valve till you need to change the oil. When you do ,pull the plug and install a 6" nipple and that should get it out far enough to catch it all in a drain pan. BTW, after you run it alittle while I would change it again based on the previous owners approach to basic maintenance.
Greg
 

ehpoole

Administrator
Ethan
Sorry for the delay in replying...

3) A #12AWG is adequate provided that the length of the cord is kept short. However, if the cord will be more than 5-6ft then you would be better served with a #10AWG cord and a 25-30A receptacle and circuit breaker. A short power cord (if plugged in) is covered by UL code and is more concerned with managing voltage drop than a hardwired Code circuit -- but if you are going to hardwire the compressor then go ahead and wire with #10AWG copper all the way. I haven't decided exactly where I will place the compressor in my shop yet...assuming I can get it running but for a 15amp motor, wouldn't #12 and a 20-amp receptacle (and breaker) be sufficient? I don't intend to wire a very long cord to the compressor. The main 200A panel (not a sub panel) for my house is in my shop so the maximum run from the panel to the receptacle would be no more than 20 feet.

#12AWG copper is fine if the cord is kept short in length (no more than say ~6 ft). If you need to run a longer distance then it would be best to upsize the cord by an additional gauge stepping to minimize the voltage drop (esp. on startup).

While the motor may only draw 12-15A when running, compressor motors are somewhat unique in that they have to start up and immediately begin working against a significant load (esp. when the tank is already pressurized). For example, my 3KW (~3.75HP) compressor motor draws about 15A when running, but for a second or two on startup it will draw a peak of 70-80A (the "Full Locked Rotor" rating), which can cause quite a lot of voltage drop on a lighter wire gauge.

As for the circuit breaker sizing, if your current 20A breaker and receptacle/circuit and #12AWG wiring are sufficient to allow the motor to instantly start (with a pressurized tank) without struggling and you do not encounter issues with your breaker tripping on startup then all will be Ok as is and no need to change anything. However, if your motor struggles to start when the tank is pressurized or your breaker is tripping, then you will need to upsize all your wiring to #10AWG copper and a 25A or 30A circuit breaker to handle the startup loads without tripping. (Note: this would also entail the use of a 30A receptacle if this is a plug and receptacle circuit rather than hardwired.)

However, if you measured the actual running amperage of your motor (with a clamp-on ammeter), I suspect you will discover it is far less than the motor's plate suggests. My compressor has the same size (2.98KW) motor as yours and mine produces about 25-30% more SCFM than yours and can charge my 80gal tank to 150+PSI in about the same time as your 60gal tank reaches 115PSI. So your amp draws may be a good deal lower than the motor is rated for.

6) For the filter you can use an OEM replacement filter or you may find that your local automotive and/or lawnmower shop may have suitable replacements. Choose a filter with at least as much effective surface area as the OEM replacement, or even more if you wish, just don't opt for less. Just doing some poking around on Amazon, it looks like Solberg filters are decent quality? I guess I am supposed to consider the SCFM rating on the compressor to get the proper filter size? For this compressor it seems that the Solberg FS-10-050 would be appropriate.

The particulars of the filter aren't real critical so long as they do not add significant resistance at the intake (which can damage the reeds and result in burning more oil). The filter has two real purposes: 1) prevent large and/or sticky debris -- and especially damaging paint overspray -- from entering the intake and gumming up or damaging the reeds and 2) quieting the compressor noise, much of which escapes via the intake opening. Specs like "1 micron" are of no consequence or concern with a filter like this as the filter's only purpose is to protect the reeds and quiet the compressor -- the compressor won't much care if some 0.001mm dust finds its way in as it will just pass through the system without consequence. So the most important parameter is adding as little intake resistance as possible (when in doubt, go a little oversized).

I recall you commenting that your current pressure switch cut-in and cut-off points are 90PSI and 115PSI. I would change these to at least 100PSI and 125PSI if it were my compressor -- if not 115PSI and 135PSI (which is a really good compromise pressure range, IMHO). You really want your tank pressure to stay higher than your inline (air) pressure regulator (by which I mean the outlet regulator, NOT the pressure switch!) because there are additional pressure losses in your air pressure regulator, oil and water separator/filter and hoses. So if your nominal tool pressures are 90-100PSI (typical), you'll want at least another 10PSI in the tank to ensure there are no significant fluctuations in the air pressure delivered to your tools during use, which will help to ensure consistent and repeatable performance (especially in nailers and paint sprayers where consistency really matters).

When installing the water/oil separator/filter and air pressure regulator, the water/oil separator should come before the pressure regulator so that its pressure losses do not affect your final air pressure. You can install these at the tank, but for best performance, and optimal water removal, you really want enough line (ideally metal line for heat dissipation) for the warm compressed air to cool so that moisture can condense out first since the water/oil separator can only separate liquid water (this matters most during paint spraying and extended air use, it matters relatively little when used with impulse tools like nailers).

I do share another member's concern that the large main pulley on the compressor does not appear to be shaped as a cooling fan (the pulley's supporting struts should be angled to act like narrow fan blades so that it blows air over the compressor head). If this is in fact the case with yours, then your compressor will run much hotter than it should since there will be no significant airflow over it. This added heat will also have the undesirable effect of increasing the amount of suspended moisture in your compressed air, which means more condensate will form in your hoses and tools. You may wish to look into replacing the pulley with a suitable compressor-type pulley. You could also opt to install a small electric fan situated such that it blows over the compressor when it is running, which would achieve the same effect.

I hope you are enjoying your new compressor!
 
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