Atlas Copco wont start!!

Seekins · Dec 5, 2009

I have a fairly new Atlas Copco GX5FF compressor (9 months old) and today it decided to start flipping the breaker. this is a single phase unit with a 40 amp breaker. Nothing has changed load wise in the shop and the temperature is always 65-72 degrees inside. The compressor has continually kicked on ever 3-5 min, runs for 30 seconds, then kicks off. Works great up until now. it has a total of 390 hours on it

the oil cooler/motor and everything else doesnt seem hotter than normal and you can put your hand on everything. but if we let it sit for 20min and try again it starts up and will be fine for aprox 3 hours.

Any ideas where i should start? could it be as simple as a bad breaker?

ARB · Dec 5, 2009

Seekins said:
I have a fairly new Atlas Copco GX5FF compressor (9 months old) and today it decided to start flipping the breaker. this is a single phase unit with a 40 amp breaker. Nothing has changed load wise in the shop and the temperature is always 65-72 degrees inside. The compressor has continually kicked on ever 3-5 min, runs for 30 seconds, then kicks off. Works great up until now. it has a total of 390 hours on it

the oil cooler/motor and everything else doesnt seem hotter than normal and you can put your hand on everything. but if we let it sit for 20min and try again it starts up and will be fine for aprox 3 hours.

Any ideas where i should start? could it be as simple as a bad breaker?

Sounds like overheat.

Make sure there is oil in it.

I just went through this with my Quincy which is the same machine.

Don't trust the sight glass!!!!

Stop the machine. Remove the fill plug on top of the oil tank and stick something in to check it.

When mine started acting up I had about 1 cup of oil in it. Even though the sight glass showed that it was ok.

Seekins · Dec 5, 2009

Thanks, I will do that right now. The sight glass looks just fine !!

Any idea what type of oil they take? I dont have anything in my books that tell me an my google fu seems to be weak today.

ARB · Dec 5, 2009

http://www.toolking.com/3-7-5-hp-oil-filter-air-filter-and-oil

It's semi special oil.

Seekins · Dec 5, 2009

Thanks, I am shuffling thru the book that came with this and no where does it say what type or how much oil it should take. I should probably figure out what type of service scheduale it needs to be on too.

NewMexicoairman · Dec 5, 2009

What HP is it.

5 hp would take a 40 amp breaker and 7.5 hp would take a 50.
Also check tour wire size.

What have you been doing for maintance, the oil filter should have been changed at the 50 hour mark and the at 1000 hours and each time you would have to add oil to the compressor. The people should have supplied you with service parts or a service contract.

Andrew
The compressor guy

Seekins · Dec 5, 2009

Its a 5 and i have a 40amp breaker. Wire size i dont remember, but i believe it is 8ga. since new you can hear the wires vibrate thru the conduit when it starts the atlas copco guy said it was normal from the startup.

i have 390 hrs and haven't done anything to it. i was told not to worry about anything for 1000 hrs..

just drained the oil and it looks like about 1/2 gallon in the compressor.

MICK 1958 · Dec 5, 2009

Seekins;

since you answered the obvious question of how much oil was in the pump, my next step would be to check the oil pressure switch. it is a microswitch inside of a chamber that moves via the oil pressure. next I would check that the cut-out switch is operating as it should...

also if you have acquired 390 hours on it I seriously doubt it is a wiring, or heater problem.

as far as it overheating....check that there is no obstruction in front of the compressor itself,,,pretty unlikely you wouldn't have seen that....make absolutley sure that the tank is "water free"..have you drained the tank? sometimes the drain is opened and nothing comes out .....that don't mean there is not water in the tank.. take the drain out....I have been caught like that before....

btw...the oil is a non detergent, moisture capturing, non foaming oil....just go to your local oil supply house and ask for "AIR" compressor oil....

that's my .02

Mick

Seekins · Dec 5, 2009

water is drained twice a week and nothing is blocking the airflow. I would have noticed a heat problem this summer when it was 110 outside. The AC quit for 3 days and the compressor never missed a beat.

I am thinking it has something to do with the starter. When you try to re-start after turning the breaker back on it will try and start for a few seconds then the breaker flips. this tells me it has the juice to start, but something isn't letting it start.

this just sucks. we finally got to where we were just cranking out the parts and the compressor was the last thing on my mind.. owning a shop is sooooooo much fun some days.

mike 44 · Dec 5, 2009

Might be the check valve. Release the air from the tank with the unit shut off. Then turn the compressor back on.The tank will fill and should work normally. The check valve can be cleaned or replaced. You might want to do that while the tank is drawn down. I had to do this one time with my compressor,also a Quincy in 15 years.
mike

atomarc · Dec 5, 2009

Seekins,

It is possible for a circuit breaker to become weak and start tripping at a lower rating than it was designed for. This usually only happens after years of flipping on and off or many overcurrent trips.

Does your compressor have a unloader and does it work. After it cycles and stops you should always hear the pump unload immediately. In a stopped condition the unloader is open. If there was a leaking tank check valve it would pee through this unloader and you would probably hear it.

A compressor that kicks on as often as you describe is working very very hard! If not a mechanical problem, I would seriously consider a impending motor failure.

Stuart

MICK 1958 · Dec 5, 2009

Well that little bit of info helps alot,

get a good volt meter, go to the contactor box, for three phase, you must check BETWEEN the legs....you should have around 240 volts ac between 1,2.then between 1,3 then between 2,3...... do not check three phase to equipment ground...this will give you a bad reading....

I was speaking between L1, L2, and L3...that will be the voltage supplied from your circuit panel or transformer. if that voltage is correct next move down to the terminals marked T1, T2 and T3..check in the same manner as explained above...that will tell you if one of the heaters are open....

that should do it.

Mick

Seekins · Dec 5, 2009

Its single phase, 208 and mine measures 218. I have the correct setting on the compressor to match up with the incoming voltage. I measured the voltage the first time it tripped and everything seemed fine.

How is this compressor working hard? It is a screw compressor and designed to run in a industrial environment. It kicks on when the pressure drops to 100psi and kicks off when it gets to 140. this is not adjustable. the compressor runs for 25-30sec every 3 min. I know starting a electric motor is harder on them than running, but there is no way you could use enough air to keep this compressor running all the time as it pumps up very fast. what am i missing here? i am running it at less than 1/3 duty cycle.

MICK 1958 · Dec 5, 2009

If you could send me a pic of the wiring schematic....to my knowledge there is no 208 single phase.....220/240 is a possibility...but if it says 208 that is without a doubt three phase. and in fact it is three phase 4 wire which is a little harder to come by in older communities

I think maybe it has never been wired correctly and now the motor is toast.

a picture of the tag that is on the motor would suffice,

Mick

Seekins · Dec 5, 2009

sorry, I know i have 208 three phase and maybe the single is 220 and that's why it measured 218? electrician speced everything and set the compressor up to match the incoming voltage so i know it was hooked up properly to start with. I will see what i can find tomarow. I did feel the breaker after the list time it tripped and it was fairly warm.

Timw · Dec 5, 2009

Possibly start capacitor, that is how they will act. I have a 5hp 2 stage that the connection burned off of the cap. I fixed it with a pop rivet until I could replace it.

Clive603 · Dec 5, 2009

Seekins

Horrible feeling you are burning up the start winding. Met the let it sit for a while and it recovers for an hour or three thing before on a compressor motor with a dying start winding.

How many starts per hour is the motor rated for and what does the start loading look like?

Generally its not considered good to hit single phase motors for more than 5 to 10 starts per hour as the start windings are overloaded by design, the specification says short time duty rated which means the same thing. If this is exceeded they will overheat and sooner or later burn out. There are heavy start duty motors which will stand up better but it looks as if you are getting into 20 starts per hour territory which is pushing things. Especially with only 30 seconds run time as the start winding won't have cooled down properly between starts. Electric motors hold "deep inside" heat well and the cooling fans aren't that efficient. I've seen references that advise 5 minutes running between starts to be confident of reasonable cooling or, if the runs are shorter 15 minutes static to cool off. Obviously motor specs vary but personal experience indicates that the suggestion is a reasonable, conservative, starting point when things are just installed rather than engineered. GX5FF is in box too which doesn't help on the cooling side.

Dunno how bad the start load is on a screw compressor. Way you are running is near certain to kill the start winding on a piston compressor.

Clive

atomarc · Dec 5, 2009

Seekins,

I agree with Clive, the compressor is being over worked to run in a start/stop mode. I have never seen a industrial screw compressor that didn't have a option to run unloaded.

I sure would read the operating instructions closely, I'll bet you find a section on setting a pressure switch so the compressor goes into a unload condition before it shuts off. I installed a 15 HP IR screw recently and it was configured this way.

Stuart

MICK 1958 · Dec 5, 2009

A three phase motor will not have a capacitor, that is why they use three phase....

there is another way of checking....like I said...and I just got done looking on Atlas copco's website...can not find a listing for single phase in your model

another tool is needed...an induction amp meter... seperate the leads going into the motor...check each lead indivdualy and compare the amp draw...they should be equal....and if they are there is another problem...if the amperage is exceessive....there is a possibility there is a bad bearing on the motor or the compressor....drawing high current...and if it is in range of spec's....it is a switch breaking down...oil pressure, most likely, or an overheat switch....

they make a induction meter attatchment for my Fluke meter....I don't know what type of meter you are using....but you must know someone that has a induction meter....that way you don't have to break into the wiring..just clamp it around each lead individualy.....not all three that will give you total current draw instead of isolating the potential motor problem.

Mick

Seekins · Dec 5, 2009

this one is designed to start and stop. there is no provision to run unloaded and no pressure switch to adjust

i promise it is single phase. they dont list the option, but it is available both ways. i got single because i am limited for space on the panel.

I do see where it is 7.5hp NOT 5hp like the salesman said. my breaker is 40amp, so i will change it to 50 like suggested.

Atlas Copco wont start!!

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