Wiring Up A New Compressor

[boilermanc]

Well, a new/old compressor. I am thinking this is a wiring issue now. I have purchased a nice older Ingersoll Rand 80gal 5hp. The unit starts up and runs to about 50lbs of pressure and then starts slowly shutting down and stops. The motor trips at that point.

I have just replaced the pressure switch so don't think that's related.

Specs on the motor: 230v amp 15. I have it wired to a 30amp breaker using 10 (2) wiring. I rewired the cord as the one that was on there was a jury rigged to say the least. The new cord is a 10(2) and wired to a dryer outlet connected to that 30amp breaker.

I did not replace the wire running from the pressure switch to the motor.

What's wrong with this?

Thanks!

 

[Norcal]

Well, a new/old compressor. I am thinking this is a wiring issue now. I have purchased a nice older Ingersoll Rand 80gal 5hp. The unit starts up and runs to about 50lbs of pressure and then starts slowly shutting down and stops. The motor trips at that point.

I have just replaced the pressure switch so don't think that's related.

Specs on the motor: 230v amp 15. I have it wired to a 30amp breaker using 10 (2) wiring. I rewired the cord as the one that was on there was a jury rigged to say the least. The new cord is a 10(2) and wired to a dryer outlet connected to that 30amp breaker.

I did not replace the wire running from the pressure switch to the motor.

What's wrong with this?
Thanks!

If your motor is rated 15A* it's not a 5 HP, it's one where they played fast & loose with the ratings. Try running the compressor motor with no load, then if it works try running it but not allowing it to build pressure, & if you have a clamp on ammeter take readings both times & post results.

BTW, you said "10(2)" , 10/2 is a NM ,"Romex®" cable, or 2-wire flexible cable, either one is not a good choice as NM cable is not intended for flexing & 10/2 would be a ungrounded cord.

*A 5 HP 3 phase motor is around 15A, single phase about 22A plus & NEC table 340.238 lists it as 30.8A @ 230V.

 

[EOC_Jason]

Also with no pressure in the tank, see if you can turn the pump freely (and check oil level).

Does it look like an aftermarket motor or the stock one?

How old is it / how much use do you think it's seen? Maybe the valves are gunked up?

I too would recommend putting an ammeter on it and see how much current you are pulling. Usually you see the pressure a little higher before a motor decides to give out / overload, but you never know.

Lastly, you might want to check the pulley sizes on the motor & pump. You can measure the diameters and also look on the motor plate for the RPM speed. From there it's simply math to figure out what the pump RPM is. You can look up the pump specs on line to see what it should be. Perhaps they replaced the motor pulley and put too big of one on there so it's having to work too hard?

 

[Steevo]

The unit starts up and runs to about 50lbs of pressure and then starts slowly shutting down and stops. The motor trips at that point.

Thanks!

When you say "the motor trips" what do you mean?

Does a round, red thermal overload button on the motor itself pop out and shut off the motor?

Does it trip the breaker?

Answer to this may lead to the issue.

 

[FluxCore]

You need motor rewound or replaced.

BUT, just for grins, check/replace the 'run' capacitor

It is a "double hump" motor, right?...Those humps contain a start, and a run capacitor.

 

[FluxCore]

On a 5 HP, 240V compressor motor, you wanna hear that sucker bang when it starts..not some fluffy little grunt, and then listen to hear if it labors and slows down as it bulds pressure...nope, it's gotta sound agressive all the way to shutoff.....A sharp start-maybe even chirp the belts, then it should hit it hard and run at same starting speed hard until shutoff.

If it ain't doing all that, then first check/replace capacitors

 

[raross]

Just a quick question for someone a little of subject, at what point in HP do these compressors require a motor starter? Around ten years ago my friend that does a lot of bodywork wanted to buy a GOOD compressor. I got him a great deal on a Kellogg American in those days for around $1100 and we hauled it, had either a Marathon or a Baldor motor can’t remember, it was provided with a motor starter with thermal resets and contactor. I know see a lot of these saying “5hp 7hp peak” hooked up direct to the pressure switch? Does somebody have a chart that shows the amp draw running on 240vac single phase, in relation to HP? IE 1 hp=10,2hp=14 etc think it would be a big help for us novices? I understand the part about the bait and switch HP deal? Thanks

 

[FluxCore]

You can use a starter even on a fractional HP motor...all it does is shift starting arcs and current to a hopefully more robust and durable component....Call it a relay, or...

Call them starters/contactors or whatever..they all do the same and are actuated tru low current/perhaps low voltage signal via manual switches or system sensors...The signal is used to pull the motor line contacts together, then break them via opposing spring pressure when the controls are satisfied...."controls" can be pressure like in a air compressor, or temp like in an air conditiong system...controls are programed to operate within limits and command stuff to either turn on/off or slow down or speed up...simple, huh?

The make/break cycle of motor line current produces arc's in the contactor contacts and those arc's erode and burn the metal of those contacts...so they have a designed life cycle of so many makes and breaks...WHEN all is good.

When all is not good, those starters/contactors don't live near as long and need to be inspected/replaced often to prevent single phasing thru welded or open contacts....even slightly burned contacts cause a voltare imbalance that will cause one set of motor winds to overheat at same load as others....Voltage imbalance is the leading cause of AC induction motor failure and it is usually caused by a burned contact in the strarter/contacter...The burned contact causes a high resistance condition that causes high amp thru that one phase winding in the motor...motor overheats and usually opens internally with no arcs n sparks-it just quits...sometimes they flame really good and throw plasma

For really high amp applications like my huge chillers, the contactor life cycle is measured in double digtits..Maybe 200 hundred starts/stops.....at a point, I have to go in and replace contacts.....for home use low voltage low amp stuff, the life cycle is measured in years depending on cycles per yr/amps and volts...single phase stuff is not as critical as muli phase.....

 

[raross]

Fluxcore, Thanks for the information I understand that basically a motor starter is a relay with thermal protection, and shifts the load from the compressor pressure switch to the mainline. The problem is the normal ohms law type formulas require a PF (power factor) and EFF (Efficiency) rating to tell the amps for the real HP rating, these cheap motors on most compressors do not show either of these? If I decide to upgrade mine to a different pump I need to know the real horsepower of my motor, not the published horsepower from Sears! Thanks

 

[FluxCore]

Fluxcore, Thanks for the information I understand that basically a motor starter is a relay with thermal protection, and shifts the load from the compressor pressure switch to the mainline. The problem is the normal ohms law type formulas require a PF (power factor) and EFF (Efficiency) rating to tell the amps for the real HP rating, these cheap motors on most compressors do not show either of these? If I decide to upgrade mine to a different pump I need to know the real horsepower of my motor, not the published horsepower from Sears! Thanks

Don't make this hard.

If the manufacturer claims 2 HP, buy a switch or starter rated for 4 HP...so what if in actuality it only develops 1 HP?

You are covered as long as you go long

Too much is better even when just enuff is just right...promise....well, unless you are talking cams and carbs, then the rules change

 

[EOC_Jason]

Having a starter for 5HP is nice, but not 100% necessary for home/light duty. I think really only 7.5HP (definitely 10HP) and up are they *really* necessary.

You can usually find a start kit reasonable if you shop around. If you know what you are doing you can just buy the proper contactor, thermal overload, and enclosure.

I always try to oversize mine too if it's not too cost prohibitive for durability reasons. Obviously you want to make sure the overload will trip at the proper rating though.

As for getting a new motor. If it says "SPL" after it, forget it! Those act like say "5 SPL" is 5HP to start pumping but then once it starts spinning it's more like 3 HP. Get a good motor that has a faceplate with the proper info, if it can't tell you simple things like FLA AMPS then move along!

 

[Charles (in GA)]

If the motor does NOT have its own thermal protection internally, then you need a starter with thermal protection built into it. If the motor is large enough that it exceeds the MOTOR HP rating (not amp rating) of a pressure switch, then you need a motor starter.

This usually happens about 5 hp (true, actual hp) and is not usually needed on lesser hp motors, though there are exceptions.

Charles

 

[boilermanc]

If your motor is rated 15A* it's not a 5 HP, it's one where they played fast & loose with the ratings. Try running the compressor motor with no load, then if it works try running it but not allowing it to build pressure, & if you have a clamp on ammeter take readings both times & post results.

BTW, you said "10(2)" , 10/2 is a NM ,"Romex®" cable, or 2-wire flexible cable, either one is not a good choice as NM cable is not intended for flexing & 10/2 would be a ungrounded cord.

*A 5 HP 3 phase motor is around 15A, single phase about 22A plus & NEC table 340.238 lists it as 30.8A @ 230V.

Thanks so much for all the responses. I have been traveling this week but will try to answer back some of these.

I will try running the motor without load. I think thats worth the effort. I have to get a clamp meter to test. Might do that this weekend. I may end up having to rewire the outlet but I guess I better test all this first. I will have to look at the wiring again to answer your question. I know from 30k feet that its the orange wrapped wire from HD. Not sure if thats the Romex or not.

 

[boilermanc]

Also with no pressure in the tank, see if you can turn the pump freely (and check oil level).

Does it look like an aftermarket motor or the stock one?

How old is it / how much use do you think it's seen? Maybe the valves are gunked up?

I too would recommend putting an ammeter on it and see how much current you are pulling. Usually you see the pressure a little higher before a motor decides to give out / overload, but you never know.

Lastly, you might want to check the pulley sizes on the motor & pump. You can measure the diameters and also look on the motor plate for the RPM speed. From there it's simply math to figure out what the pump RPM is. You can look up the pump specs on line to see what it should be. Perhaps they replaced the motor pulley and put too big of one on there so it's having to work too hard?

This thing is all stock. It's in good shape. I think it's from the 80's but dont have that information. The serial number plate is long gone. The unit belonged to a friend's father who recently passed. He had used it regularly in the shop. When I drained it had very little water in it so not sure it has seen too much use of late. Long story though, it had been used recently by the people that moved into the house. So I do know that it did run well.

I will get that amp meter hooked up and see what I see.

 

[boilermanc]

When you say "the motor trips" what do you mean?

Does a round, red thermal overload button on the motor itself pop out and shut off the motor?

Does it trip the breaker?

Answer to this may lead to the issue.

Hi Steevo, yes, thats it. Sequence:

Plug in the compressor
Flip the breaker
Unit fires up hard and fast and starts building pressure. Runs great!
15 - 20 seconds in it starts to just slow down. just slowly.
slowly, slowly begins to... and then stops just like the pressure valve should shut it down when its at full pressure.
At that point the red button does nothing. push it, no click. main breaker does not trip.
wait for a little while, 10 minutes maybe... then come back and you can push the red button at that point. then start it back and it does the same thing.

hope that helps.

 

[EOC_Jason]

Yeah, the red button won't reset right away if it's overheated, you have to let it cool down first. It's a thermal overload.

Try running the motor without the belt on and see how it does. If that passes, try running it hooked to the pump, but leave the tank valve open so it builds no pressure (i.e. no extra resistance)... Put your hand over the valve though to verify if it builds pressure (Or skip that step if you are confident it was previously)...

*maybe* the run capacitor on the motor?

Maybe the check-valve? I've never heard of one getting stuck close, and you said it's building up pressure, and there should be a safety valve between the pump & check valve...


Just as a side note, did you check / change the oil yet?

 

[boilermanc]

Yeah, the red button won't reset right away if it's overheated, you have to let it cool down first. It's a thermal overload.

Try running the motor without the belt on and see how it does. If that passes, try running it hooked to the pump, but leave the tank valve open so it builds no pressure (i.e. no extra resistance)... Put your hand over the valve though to verify if it builds pressure (Or skip that step if you are confident it was previously)...

*maybe* the run capacitor on the motor?

Maybe the check-valve? I've never heard of one getting stuck close, and you said it's building up pressure, and there should be a safety valve between the pump & check valve...


Just as a side note, did you check / change the oil yet?

Sounds like some good things to test this weekend. The motor never gets hot by an means. Doesnt really have enough time to I guess. I do know it build's pressure. I can get it up to 50ish pounds. Open the valve and out it comes. I will have to check the check valve. Still feel like it might be a power issue somewhere along the lines.

As far as the oil, yes and no... I did have to add oil. It has an oil "window" on the front with a red dot. I assume that is you can could actually see into it that you put the oil level on that dot. Cant see into mine. I added oil but not sure enough or too much. I just stuck a screwdriver down to the bottom of the oil reservoir and decided that it was full enough to run. Not sure at this point how else to check it. How to order a new window for the oil I have no idea. I have no numbers on the unit.

thanks!

 

[RECox286]

The oil level "eye" could just need a good cleaning from the inside, and may

be indicative of the crud buildup you will find in the crankcase. I would

suggest a thorough flushing and refill, and while it is empty, unscrew the

"eye" and see if it cleans up enough to reinstall. It sounds to me like your

new toy was run hard and put away wet over the course of its previous life.

But, I don't think it is beyond hope. Keep truck'n.



BTW: Curious to find out what the Amp readings are. Also you may need

to replace the thermal overload. They can get weak too, just like capacitors

can.

If you have a motor shop in the area, they should be able to

diagnose the motor, and give you options as to repair/replace much

quicker than you could do it on your own.

Uncle Bob

 

[boilermanc]

Ok, was able to do a little more testing. First, let me walk through what I have setup. I think I had a few things mixed up before. I still think its just a wiring issue to the motor...

at the breaker box i have a double pull 30amp breaker. think thats ok.

from there i ran 10(3) cable to a dryer outlet. not sure on this one...

i rewired the plug on the compressor with a 10(2) cable that then plugs into the dryer outlet.

i replaced the pressure regulator but did not rewire to the motor.

so today i was able to get a clamp meter and tested. here is what i found...

i set the clamp meter to 200v (correct?)

on the black wire i start off with roughly 45.1 amps and then drops to around 41.1 as is starts to slow down.

on the white wire it starts off over 46 and then windes down to around 44.8 right before it stops.

i did notice this time that wires/motor do get hot - well warm. doesnt really have time to get "hot" before it shuts off. again, makes me think it's a wiring issue.

i was going to try to get the belt loose to run it but had trouble with a couple of bolts so left it for now.

by the way, its a single hump.

if some pictures would help, let me know.!

thanks!!!

 

[boilermanc]

Sorry for the delay with updates. I have to travel a lot and not always home to work on this stuff.

I was able to run the motor with no load. Ran perfect! Pulled a perfect 15amps.

I changed the oil and that seemed to make things a little better as it ran for maybe two minutes now but then it still starts to slow down and then stop well before it is full.

I need to run it with the air valve open and see what happens. Where else should i look for issues?

thanks!

 

[boilermanc]

Was able to do some more testing today. Still in the same situation where it starts up, runs and then slowly shuts down. Wait a few minutes and I can trip the red reset button on the motor and it takes on the same cycle.

I pulled the release pin to let the air out and ran it with it open. Fires up fast and hard. Runs for a good minute at least real hard. Then just stops. Bam. Wait for a few minutes and press the red button and can do that all over again. The motor never gets hot and the compressor runs hard.

ideas at this point?

thanks!

 

[KinzeMech]

on the black wire i start off with roughly 45.1 amps and then drops to around 41.1 as is starts to slow down.

on the white wire it starts off over 46 and then windes down to around 44.8 right before it stops.

That's way too many amps for a 5 hp, 220v motor.
It also does not make sense that the amps are falling off as the motor is loading up.

Try checking voltage on the load lines going to the motor, as it is running. If there's a poor connection somewhere and the motor is getting poor voltage, that would explain why it starts, but falls flat on it's face as load begins to build.

 

[boilermanc]

that was a great thought. I went and checked a few measurements.

i found that with the compressor hooked up with the valve open i still pull 40+ amps on the white and black wires. so yeah, not good.

i stripped the belt off and ran the motor again without it and the motor just humms along but both wires pull at 2.3 amps? would that be right? in any case, it never shutdown and i let it run for probably 5 minutes with a steady 2.3 amps.

not sure where to turn next...

thanks!

 

[mrb]

is the pulley ratio wrong and putting too much load on the motor?

 

[KinzeMech]

Since this is a used compressor, are you certain the pulleys are the correct size? A too large pulley on that motor would definitely cause this problem.

How freely does the pump turn by hand? With 0 psi in the tank it should turn pretty freely by hand.

 

[KinzeMech]

Unhook the output line from the second stage cylinder, and let the compressor run, with the output just dumping out to the atmosphere. It should take very little power to turn at full speed that way.

 

[boilermanc]

Ok, good, little by little. I took the coupling loose to allow the air directly out of the compressor. Runs fast and hard and blows out hard and just keeps on going. I checked the amps and it pulls 14 on both wires.

So good to that point. Issues lies on up stream but what to try next?

thanks!

 

[mrb]

what psi is the tank at when the motor starts drawing alot of current and the O/L trips?

 

[EOC_Jason]

Check Valve maybe?

 

[Aceman]

I'd lean towards pulley sizes myself. A motor pulley only slightly oversized(or compressor pulley undersized) can increase motor current exponentially.

I would do everything in my power to find the original pulley sizes, whether by old manuals or calling IR directly.

 

[KinzeMech]

Look for a restriction somewhere in the plumbing between the pump output, and the tank. It's going to be difficult to help you hunt for that one online, as plumbing varies widely from one compressor to the next. If this used compressor has sat for a while, it would not be uncommon for the unloader valve to need to be disassembled and cleaned. When condensate dries onto them, it can leave sticky crud behind, and the valve will no longer open fully.

 

[boilermanc]

Thanks so much all, here is some more information...

took the tube that runs to the pressure switch off and it runs fine. air comes out of opening and it runs at 14amps. Never shuts off.

i can open up the valve in the front of the compressor and let air run and it runs just fine. 14amps and wont shut off.

when i put the tube back on for the pressure switch and close the front valve so that it starts building pressure it will build to 20lbs and then shut off. i do not have the pressure switch connected into the actual switch. just sitting loose if that makes sense.

always seems to shut off right at 20lbs. i checked all the tubes and there is not anything blocking any of these.

really confusing.

thanks!

 

[boilermanc]

what psi is the tank at when the motor starts drawing alot of current and the O/L trips?

seems to always be 20lbs.

 

[boilermanc]

Look for a restriction somewhere in the plumbing between the pump output, and the tank. It's going to be difficult to help you hunt for that one online, as plumbing varies widely from one compressor to the next. If this used compressor has sat for a while, it would not be uncommon for the unloader valve to need to be disassembled and cleaned. When condensate dries onto them, it can leave sticky crud behind, and the valve will no longer open fully.

where would the unloader valve be?

 

[KinzeMech]

what is the voltage across the hot lines to the motor while pumping free air with the tank valve open?
what is that same voltage again, while building pressure, just before the motor trips?

 

[KinzeMech]

where would the unloader valve be?

sometimes it's on the line from the pump to the tank, other times it can be built into the pressure switch.

Usually it's a combination check valve/unloader valve. It holds the tank pressure, and bleeds off the line pressure to the pump, so when the pump starts up, it's not pushing against pressure.

 

[pop pop]

If this unit gets started and can reach 20 - 40 psi, the unloader valve doesn't sound defective, or at least not causing this problem. Fully unloaded, 14 amps on a 15 FLA motor doesn't sound good. I'm checking the run capacitor before moving to the next step.

 

[boilermanc]

Thanks for eveyone's help on this. Sorry so long in posting but tough with travels and just time to work on it.

I did find out that the motor is fine. I had it bench tested and the boss says its good to go. I replaced the capacitor and he tested both old and new and they were both fine.

I am going to start a new thread with where I am now and post some pictures with it.

thanks again for everyone's help!

 

[EOC_Jason]

I remembered this old thread and thought I would post my comments since I kind of went through a similar ordeal this weekend.

My Craftsman 60 Gallon Fake "6HP" (15 AMP) has been acting up where the motor just spins real slow at first and eventually it gets up to speed. The tank is dated 93 and I'm pretty sure everything on it is original.

Finally it got to the point the motor would BARELY start turning and eventually just stopped. Had some spare capacitors so I swapped out the Start & Run caps, still no good.

Broke down and got a new 5-SPL Leeson motor from Northern Tool for $235 + Tax. Should be a straight swap everything mounted up the same.

Swapped out the motor, re-did all the electrical wiring since the person before me was too cheap to use any connectors. (I got the compressor for free, so I can't complain). Aligned the belt as per manual, made sure everything was good to go, put back in its corner.

Fired it up... Started out good... around 40 PSI is started to slow down just like before! *grumble* Started making a little squeaking sound too... Thinking maybe it could be a bearing, or maybe I didn't tighten the belt enough. After about 10-20 seconds the speed picked back up to normal.... and as it was filling up it would randomly slow down then eventually speed back up... at 120 PSI the motor sounded like it was about to stop completely... *grumble*

WTF... It's a new motor so why is it doing this?!?!?! AAAHHHH...

Okay... Drained tank completely. Turned on with the valves open so it wouldn't build pressure... Ran great... Closed valves... started building pressure... 40 PSI it did the exact same thing slowing down! I turned it off and unplugged it. Tried turning the pump by hand and it seemed okay, nothing binding. Plugged back in and turned on.. Started out slow, eventually sped back up... Did the same thing as before would slow down at certain points but eventually speed back up...

Hmmm... Well let me pull the top off and see how bad of shape the reeds are in and the pistons and cylinder walls... Was very careful not to tear the gaskets so I could put back together. First off, there was a staple that was caught in one of the intake reeds, so right there I'm loosing efficiency! Pull the 2nd plate off... NASTY! Totally caked in carbon buildup. However the reeds were functioning and not broken or anything. Piston tops were dirty as well but the cylinder walls looked good. I cleaned everything best I could without breaking it down any further. Carefully re-assembled everything and plugged it back in.

Just for good measure I also changed the oil. Put in some Amsoil air compressor synthetic I had left over from changing a friend's compressor in his shop.

Fire it up again... Started out sounding REALLY good... Could definitely tell cleaning that crud out made a difference. Then just after 40 PSI is started slowing down again... AAAAAAAAAAHHHHHHHHHHHHHHH....

Okay... figure I would check all electrical stuff. Checked ALL connections in the cord, the plug in the wall, even the wires at the breaker... All good. Turned on the compressor and checked voltage and amperage draw... all good... even when it slowed down the amps were steady... weird...

Shut it down and went inside. Did a little google searching and came across a couple posts specific to the craftsman compressors talking about how if the belt is loose the motor will go up and down in RPM and also you get the belt squeaking sound. Okay, well I thought I had the belt tight enough (as tight as it has always been). But what the heck do I have to loose. I couldn't tighten it anymore with the belt on, there just wasn't any place to get leverage. So I took the belt off, made a guestimate and re-tightened the motor down after making sure it was square. Put the belt back on and it was MUCH tighter. Double-checked alignment.... good enough... Opened valves... plugged back in and flipped her on...

BAM... starting out strong... sounds even better than before. Okay... close the valves and took a couple steps back... Slowly built up pressure... sounding good... reaches 40 PSI... KEEPS CONSTANT RPM! Yippee! Continue to watch it build pressure... no slow downs at all! Cuts off at 120 PSI without issues!

As crazy as it seems, I would have never guessed a loose belt could have caused the motor to hesitate like that. Now I'm not really 100% convinced the old motor was bad... Sure it was 20 years old... But it was doing the same thing as this new motor did when the belt was loose. Guess I'll keep it around until I can find a day to use / test it out, but right now the compressor is running good so I'm not messing with it anymore! I'm going to re-check the bolts on the head to make sure they are tight, then I'm putting it back in its corner and calling it done!