Air Compressor Issue

[Doppleganger]

Ok....at the point of getting my compressor broke in and ready to paint my SB. I dont have 220 so was going to use my generator. 7500w/9500w surge - runs our 1400sqft house (AC, fridge, 3 freezers) with ease.

I started the generator and let it run for about 10min. Then plugged in the compressor and waited another 5-10min before flipping the switch. Compressor started up but I could hear the generator dipping here and there under load. The compressor motor is new - the pump was rebuilt (rotated by hand real smooth). Everything is new.

Had 20psi at the gauge for the tank in about 3 min. Ran nice but could hear a low buzz (hard to tell where with a generator running) - motor or pump? Compressor shut off and will not start again. The breaker on the motor isn't tripped. No idea.

Wife and I have an agreement that if the truck is not in 're-assembly' mode this year (which requires the cab to be in color and on the frame - cant afford a shop but have the paint and everything but a compressor now to do it), its time to bail. If no ideas to save the day (and very likely the project), my next 'guess' is to remove the motor and take it to the (VERY good) shop that rebuilt it - see if something failed on that end.

If I had anything of universal value, I'd offer a reward for the holy grail of solutions.

ANY ideas? TIA

 

[legopnuematic]

Pictures? Does the compressor have a magnetic starter?

Horsepower of motor?

 

[Bextreme04]

Ok....at the point of getting my compressor broke in and ready to paint my SB. I dont have 220 so was going to use my generator. 7500w/9500w surge - runs our 1400sqft house (AC, fridge, 3 freezers) with ease.

I started the generator and let it run for about 10min. Then plugged in the compressor and waited another 5-10min before flipping the switch. Compressor started up but I could hear the generator dipping here and there under load. The compressor motor is new - the pump was rebuilt (rotated by hand real smooth). Everything is new.

Had 20psi at the gauge for the tank in about 3 min. Ran nice but could hear a low buzz (hard to tell where with a generator running) - motor or pump? Compressor shut off and will not start again. The breaker on the motor isn't tripped. No idea.

Wife and I have an agreement that if the truck is not in 're-assembly' mode this year (which requires the cab to be in color and on the frame - cant afford a shop but have the paint and everything but a compressor now to do it), its time to bail. If no ideas to save the day (and very likely the project), my next 'guess' is to remove the motor and take it to the (VERY good) shop that rebuilt it - see if something failed on that end.

If I had anything of universal value, I'd offer a reward for the holy grail of solutions.

ANY ideas? TIA

Best guess is that the generator and/or compressor are not wired correctly for what you are trying to do. My 60 gallon compressor with a 6hp 220 motor will run fine on my 9.5Kw generator. It should only surge the voltage at the initial startup of the compressor and run fine after that. Pics of the compressor plug/wiring/identity plate and the same thing on the generator would be helpful.

 

[Doppleganger]

Best guess is that the generator and/or compressor are not wired correctly for what you are trying to do. My 60 gallon compressor with a 6hp 220 motor will run fine on my 9.5Kw generator. It should only surge the voltage at the initial startup of the compressor and run fine after that. Pics of the compressor plug/wiring/identity plate and the same thing on the generator would be helpful.

I'll get some pics of both and post them shortly. THX

The motor is getting juice but is dead as a door nail. Breaker never flipped (on the motor) either. Shop told me to bring it to them - going to drop it off tomorrow AM.

This (1996) motor was made in MN. Had a disk on the tail end of the shaft - looked like bakelite. They said it was something like a governor (?) and weren't made anymore (mine was cracked). They said they updated it with something newer and better. Wondering where that part came from and if thats what failed. Will soon find out.

If its the switch - that can go. Never cared for those little flip switches that look like a bent coat hanger. Would like to put a box and actual breaker on it like the nicer models.

 

[legopnuematic]

What you are describing is the centrifugal switch/start circuit switch.

A single phase induction motor is unable to start it self, so they use capacitors and a start winding to get things moving and as the motor comes up to speed, the switch will cut off the start circuit and the motor will be running on the run windings.

When the motor shuts off, and you hear that click spinning down, that is the switch reconnecting the start winding.

So if the motor is overloaded, or undervolted, or bearings are bad, it will create a condition where it is unable to come up to speed, thus not throwing the centrifugal switch and keeping the start winding energized too long. Too long can burn the start windings (if you were to open the motor, they are the thin windings, since they only need to be on for a brief moment), or too slow to get out of the start circuit can wear/erode the switch contacts prematurely due to not being thrown fast enough. Creates arcing etc.

If the compressor is of a decent size, 3 to 5+ horsepower (real hp, not sears peak hp bs), it should be ran through a magnetic starter, with properly sized heaters. The pressure switch should control the mag starter.

Unfortunately most cheaper compressors forgo the mag starter and run the load through the pressure switch, which is hard on the contacts. Lots of people say they have had one running that way for 100 years and never had a problem, but a properly sized mag starter/heaters is the right way, even if the motor itself has a klixon switch (the little red reset button). IMO

 

[Doppleganger]

Pics of the compressor plug/wiring/identity plate and the same thing on the generator would be helpful.

Hoping this is what you are referring to.

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fwiw.....realized after the fact that the 30A breaker on the generator was tripped. At least I know why the motor stopped, but why it tripped it.....is another question.

 

[legopnuematic]

The good news is your compressor is actually 5hp, not just some marketing baloney. 22 amps @240v is 5hp.

The thing about induction motors that have to start under a load, like an air compressor, is they draw a lot of amps on startup. So much so that the NEC allows for a dedicated motor circuit to have a breaker that is upsized to 250%. My own compressor is a 5hp motor, 24 amps, I have it on a 50 amp breaker. That works for my setup and I have not had any nuisance trips.

The "locked rotor" or instantaneous amperage the motor will draw can be (for example a 5hp motor @24 amps) close to 100 amps. Now that is only for a small fraction of time, but depending on the breaker, can cause a trip. That is likely why the 30A breaker tripped on your generator. Too much pork for just one fork. Also to factor in how long of a run for a cord, as too long or undersized can create voltage drop/heating of the cable quickly.

Another thing to note is that while by amperage Nema 6-50/14-50 plugs and receptacles are rated at amperages above your 22 amps, they are only rated to 3hp. Above 3hp needs to be hardwired or use high $$ pin and socket type plug and receptacle. The NEC has this as if a 5hp (or 10etc) motor was to be plugged in or unplugged under load, there is a potential for a bad arc flash, that is a bad day for the guy holding the plug. Just something to note.

One option, is to look for a gas engine drive compressor. I got a used harbor freight 13hp 30 gallon unit 4 or 5 years ago and it makes enough air to sandblast, paint, do anything really. It lives in the bed of my 76. Around here at least they seem to hold their value well enough, you may be able to pick one up near you for a good price, use it to complete your project, and sell it for what you have in it or even possibly a small profit.

Another option may be to underdrive the pump, with a larger pulley on the pump, or a smaller one on the motor. Also is the motor is 1725rpm motor or 3450rpm?

Another, another option may be to set it up for continuous run, with an unloader valve like an engine drive unit, that negates the high load spikes for having to start the motor under a full tank of air.

The above ideas also assume the unloader and check valve are functioning correctly on your pump too.

 

[Doppleganger]

The good news is your compressor is actually 5hp, not just some marketing baloney. 22 amps @240v is 5hp.

The thing about induction motors that have to start under a load, like an air compressor, is they draw a lot of amps on startup. So much so that the NEC allows for a dedicated motor circuit to have a breaker that is upsized to 250%. My own compressor is a 5hp motor, 24 amps, I have it on a 50 amp breaker. That works for my setup and I have not had any nuisance trips.

The "locked rotor" or instantaneous amperage the motor will draw can be (for example a 5hp motor @24 amps) close to 100 amps. Now that is only for a small fraction of time, but depending on the breaker, can cause a trip. That is likely why the 30A breaker tripped on your generator. Too much pork for just one fork. Also to factor in how long of a run for a cord, as too long or undersized can create voltage drop/heating of the cable quickly.

Another thing to note is that while by amperage Nema 6-50/14-50 plugs and receptacles are rated at amperages above your 22 amps, they are only rated to 3hp. Above 3hp needs to be hardwired or use high $$ pin and socket type plug and receptacle. The NEC has this as if a 5hp (or 10etc) motor was to be plugged in or unplugged under load, there is a potential for a bad arc flash, that is a bad day for the guy holding the plug. Just something to note.

One option, is to look for a gas engine drive compressor. I got a used harbor freight 13hp 30 gallon unit 4 or 5 years ago and it makes enough air to sandblast, paint, do anything really. It lives in the bed of my 76. Around here at least they seem to hold their value well enough, you may be able to pick one up near you for a good price, use it to complete your project, and sell it for what you have in it or even possibly a small profit.

Another option may be to underdrive the pump, with a larger pulley on the pump, or a smaller one on the motor. Also is the motor is 1725rpm motor or 3450rpm?

Another, another option may be to set it up for continuous run, with an unloader valve like an engine drive unit, that negates the high load spikes for having to start the motor under a full tank of air.

The above ideas also assume the unloader and check valve are functioning correctly on your pump too.

Here's a pic of the pullys, the motor tag and the centrifugal switch that was broken that they updated.

The unloader and check valves are both new - whether they are working properly...dunno.

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[Bextreme04]

I'll get some pics of both and post them shortly. THX

The motor is getting juice but is dead as a door nail. Breaker never flipped (on the motor) either. Shop told me to bring it to them - going to drop it off tomorrow AM.

This (1996) motor was made in MN. Had a disk on the tail end of the shaft - looked like bakelite. They said it was something like a governor (?) and weren't made anymore (mine was cracked). They said they updated it with something newer and better. Wondering where that part came from and if thats what failed. Will soon find out.

If its the switch - that can go. Never cared for those little flip switches that look like a bent coat hanger. Would like to put a box and actual breaker on it like the nicer models.

Best bet is to get your multimeter out and check whether you are actually getting 220. Are you sure you connected it to the 220 circuit on the generator? That generator should be able to provide 240V/31A continuous and 240V/40A peak... which should be plenty for a 22A electric motor.

 

[Doppleganger]

Best bet is to get your multimeter out and check whether you are actually getting 220. Are you sure you connected it to the 220 circuit on the generator? That generator should be able to provide 240V/31A continuous and 240V/40A peak... which should be plenty for a 22A electric motor.

Have a 45 yr retired electrician friend coming over to double check everything I did. I'm pretty sure its all correct, but after this.....dunno. Need a second opinion. lol

 

[82sbshortbed]

Can you buy a soft start for the compressor like for your ac?

 

[Doppleganger]

Well, it all works now - was a semi-dumbarse mistake involving an extension cord with 2 grounds instead of 2 hots. Also with about 60ft of sweated copper, I found 1 leak - easy fix (he said) tomorrow.

Only thing I noticed is the pump (which you can rotate by hand real smooth) is very loud - and while it ran for about 10 minutes....I watched the new oil in the site glass go from clear-caramel to pitch black. Wondering what thats all about and should I change it again.