HELP!! compressor motor woes...

i'm at my wits end with this thing. i'll try to explain the situation as best i can...

just a couple weeks ago i replaced the electric motor on my shop air compressor. the motor is a 5hp, 21 or 22amp (i forget), 220volt, continuous duty compressor motor. the last one was running one day when it just froze up and all the smoke got out. it was only a little over 2 years old. and was the exact motor i have now... but back to my current motor...
last night i'm in the garage after an entire day of body work. i use the blow gun to blow the dust off the car when the comp kicks on. or at least it tries to. it sits there humming and trying like hell to turn but just can't do it until finally my 30amp breaker trips. i reset the breaker and try again with the same results.
now. the compressor pump is NOT locked up and stalling the motor. i can turn both quite easily by pulling on the belt. and here is where it gets interesting. when that last motor went out a couple weeks back (this was only my second day using the new motor) the first replacement i got did this exact same thing right out of the box. we did everything we could think of. checked the connections in the breaker box, disconnect box and pressure switch as well as the motor. then we checked to make sure both legs had 110volts. everything checked out perfectly so i took the motor back and exchanged it for this one. i hooked it up and it ran flawlessly... till last night.
another note that may or may not be related. the original motor that went up in smoke had been having trouble starting since it was only a couple months old. it would often trip the breaker when trying to restart and it would dim the lights in the garage when it did. i had taken it to an electric motor shop and the guy told me there was nothing what so ever wrong with it. i explained the problem to him and he said i was only getting 110volts to the motor. i checked it and that was NOT the problem. so i just dealt with it... until it finally blew.
all 3 of these motors were the same brand (GE if i remember right) that i bought from Tractor Supply.

anyone got any ideas?? even my electrician friend is at a loss.

thanks

 

Not sure but mine compressor did the same thing last week, just sat there trying to start but just smoked and made a bunch of noise. I also had a bunch of problems wiring a 3 phase motor in my lathe. If you haven't already, check and make sure all the wires inside the motor are connected properly according to the diagram on the motor plate. It may be a high voltage/low voltage problem. Then when you start the motor check the amperage it draws making sure its not exceeding what the motor calls for. Go from there.
Good luck

 

You need to get an unloader pressure switch (Not sure of the proper name). Whats happening is the pump is on a compression stroke and the motor, when starting, can't overcome the compression. The unloader will vent the pump until the motor gets going and then it closes and allows the pump to build pressure. Or you can ***ist, when the motor tries to kick in give the pulley a spin (WATCH YOUR FINGERS). Same thing went on with my compressor, breakers will trip when motor is new but after awhile the motor will let the smoke out.

 

im no electrician, but i think you need a capacitor starter for that. one came with the compressor ive got. (5 hp 220 single phase)
correction...its not a capacitor. the capacitor is on the motor. it says... single phase starter, FURNAS catalog no 16cf15bgacf.

 

Just a thought, is the motor a single phase, or a 3 phase unit?

 

I'm kinda with you on this,either the unloader or,possibly the check valve on the tank isn't doing it's job.

 

You did change the capacitor with the motor right?? Compressors need a surge to start thats what the cap is for, and by what you've said, the cap is bad and caused the first failure

 

Are the wires big enough for the load? They should be at least #10 AWG. Another thing, how far from the panel is the compressor?

 

A friend of mine had the same problem,, 3 motors from tractor supply,,, He found his problem was wires on his breaker were loose. Need to check all connections and any piggy back connections need to be eliminated. Also could be the unloader switch. That is my 2 cents.

 

(Me=30+ years electrical Licensed sick old electrician)

Take the belt off it.. check all connections according to motor name plate.. Roll the compressor over by hand.. if it is stuck.. you got mechanical problems..

NOW single phase.. short explanation on test..
Take belt off.. turn on motor.. start spin it by hand, keeping fingers attached .. if it runs it is the starting circuit.. a capacitor-winding-points series circuit dealie. (the circuit goes through all them).
NOW, you can check wiring in the order on the nameplate drawing.. winding, ohm out with meter to check to make sure it is not burned out.. It's job is to "angle" the electrical waves coming into the motor to provide starting.. Check the capacitor with the ohm meter.. dissconnect the wires, turn leads on ohm meter around.. it should 0-then swing to infinity.. or 0 to high on digital meter.. NOW the points.. you can open them by hand or with a piece of paper to check to make sure they are conducting.. When the motor comes up to speed it opens the points with a centrifugal unit to dissconnect the start winding..

One thing interesting, changing the winding-capacitor way it ties into the power switches the direction the motor starts.. without starting it with the winding it can run in either direction..

I had one under my eave for a few years, was painting a car and the points were corroded.. I had paint mixed up and threw a temper tantrum like a 5year old..

Took the end off the motor where the push ****on overload reset was.. Took a piece of paper and rubbed between the points till they were slick.. painted the paint out and smiled.. THEN ORDERED a EatonCompressors 7 1/2 hp V4 w/vertical tank.. man was that thing heavy..
It has worked flawlessly.. paint was still wet on the tank when it got here thou.. Someone said they are using a foreign supplier for the pumps.. I think, thought they are all USA made.. THE owner of the company will talk to you on the phone..

If you can't figure it out any further, I can talk you through it.. Don't mind if I ain't busy, if I am, I will tell you so.. Pm me..

David....

 

I think you're right on! My old compressor has an off breed motor with twoi sets of capacitors inside its box: one set to start on; one set to run on. There's a switch in there that reads voltage in the two circuits and switches from one to the other as required. Every now and then it sticks in the run position and causes the motor to growl and fail to start until it trips the breaker. I go tap on the switch with a screwdriver handle and it jars it enough to fall back into start position. Troubles over (until the next time it sticks. I should dis***emble the switch and clean the contacts.)


e=Da Tinman;3623691]You did change the capacitor with the motor right?? Compressors need a surge to start thats what the cap is for, and by what you've said, the cap is bad and caused the first failure[/quote]

 

my vote is its the unloader. when your compressor stoped under normal operation did you hear the unloader unload?, its the sound of air pleading off, peesssssssyyuuuooooo...lol

 

I had the exact same issue. The guys here on the HAMB were able to help me out.

Mine was the compressor unloader valve which dumps the head pressure so the motor can start the compressor without 90psi pushing down on the compressor piston. Mine would just grunt then pop the breaker. Mine is a 5hp 220v 1 phase motor also.

You can test it by dumping all the pressure in the tank, and then seeing if it will start. If it does, its the unloader valve is stuck.

After I replaced the valve, it was as good as new.

 

On mine it was the starter switch. The kick on pressure was too high. Blew fuses every time it went to start. I reset the switch to a lower start up pressure and has been working fine ever since. Believe me when I say it was trial and error time. Blew lots of fuses until I got it right.

 

Most single phase compressors dont use a starter they just use a pressure switch.. That is unless you have fooled with the pressure switch and your trying to start under too high of pressure..
Dave

 

Also try and find a clamp on ammeter and see how much the motor is drawing when it tries to start ..
Dave

 

My vote for the unloader valve too. It acts like a compression release so the pump has 0 resistance when starting up >>>>.

 

Please let us know what you find..... Thanks.

 

You say that it is supposed to draw 22 or 23 amps running and you are using a 30 amp breaker. I wonder what the start up current is and if it is over 30 amps. It may need a 40 or 50 amp breaker to give it enough juice on start up. I am not an electrician, just my $.02

 

I didn't know what is was called, just a switch to me. I am not any kind of electrician. The setting on it was factory also. Nothing I did to it. Now I know it is a pressure switch. Thanks.

 

"....the first replacement i got did this exact same thing right out of the box. we did everything we could think of..."


I ***ume at that point, you had an empty tank from the first motor dying. If so, my money is on an electrical problem, not the pressure unloader especially if you can easily turn the belts by hand. David E. seems to offer sound advice. Good luck

 

YA MOST 230 SINGLE PHASE COMPRESSORS JUST USE THE PRESSURE SWITCH BUT IN SOME CASES THE MANUFACTURES DO PUT A MOTOR STARTER ON SOME OF THEM Damn caps lock.. A motor starter is just a fancy relay of sorts that turns on and off by a control circuit of some sort like a pressure switch putting power to the motor when required..Im no electrician either but i spent a few years getting trained by a master electricain. I shoulda started earlier and got my card but it never happened and now after 31 years i need a job ?... Oh well its on my resume that i know the **** anyway.. Id look for an unloader also on the compressor but on the other hand ive seen 2 or 4 bad motors in a row... Ill bet GE dont make em here anymore..
Dave

 

The breaker could be weak if it is old,but i would check the tank check valve,all single phase compressors come with the unload feature on the pressure switch.is it constantly blowing down?or not at all?they will vibrate out of adjustment so the armature wont hit the schrader core.after you check those things i would go to the capaciters on the motor.i install build and repair compressors for a living you can pm me if you need more help!

 

Also one other thing,these motors will often pull 4 -6 times name plate amperage on start up!take the amp rating on the tag then find the sf rating probably 1.15 service factor multiply it ex (22ax1.15=25.3)wich means at highest unload point it will be pulling about 25 amps.a 30a breaker is being abused at this point.see if you could step up to 50a,i know it seems big but a small problem will trip it before you have major meltdown for sure.it does not take much to increase amp draw.if you have an amp probe on your meter check your amp draws at start up and shutdown.

 

went out there today and it fired up just fine. used it all day with no issues what so ever. started flawlessly at least a dozen times today.

connections are ALL tight. checked them twice.

wires ARE in the correct location. i took a picture of the old one before i unhooked it. not too many ways you can hook it up anyways.

the compressor pump spins freely. i even grabbed it while the motor was struggling and it spun very easy. i was able to kinda give it help to start by spinning the belt by hand (on the last motor that i returned). so that rules out the unloader valve. that was about the first thing i thought it might be. it is an Eaton 3 cylinder pump i bought 3 or 4 years ago. super nice unit. i did a TON of research before i bought that pump.

on the last motor that was doing the same thing (the one i returned) i emptied the compressor of ALL air and it still would not start without help.

the capacitors are on the motor and are just as new as it is.

the check valve i replaced not long ago. don't see how that would be an issue anyways, every thing is working fine in regards to that.

the wiring in the garage is up to snuff (i believe it is #10). my electrician buddy helped me do it all almost 8 years ago.

it is a single phase system and so is the motor.

there is no starter switch. it uses a pressure switch and that was replaced less than a year ago.

the 30 amp breaker is probably overkill. i installed it when the other motor (the one that lost all it's smoke) had issues and was tripping the breaker every time. i'll look into that further but i'm certain that is NOT the cause of the problem. i'll figure out what it should have and change it out if need be just to be on the safe side though.


any other ideas??? ...i guess until it does it again i won't worry about it... much! damn this is aggravating!!!

 

My old compressor did something like you're describing, but it was all temperature related, if it was freezing cold out,she didn't want to turn over.My cure was a new compressor.

 

These motors have a start switch, Its hooked to the mechanical weights on the end of the armature. When stopping you can hear them close, and the weights close the contact switch and give the start capisitor current to start the motor. Once it starts to spin, about 3/4 of total rpm the weights open the switch taking the capisitor out of the circuit, Its not needed, Its bakalight cause it only works for a few seconds. Run capisitor are tin cans cause they are in the circuit as long as it runs.If that switch stays open the motor cant start, and the motor will hum cause its dead to start, don't have the oumph it needs to start, it needs the capasitor. 3 phase motors don't need any thing to start, if wired correctly and have the correct power to them they start, NOW. But theres Hi and LO 3 phase, 208/230. 208 in more of a problem for starting but usually does it job.

 

CAUTION 3 phase motors need phase protection, If you loose 1 leg you now have single phase,and if the motor tries to start, give it about 5 seconds and its toast. So you need 3 phase protection, to protect the motor, most have it, but it must be in place at all times. NOT a Mabye.

 

not all motors are the same, graingers has pretty good motors, just cause it has a h.p. rating, rpm and amp motors are still different,

to over simplfiy there are high torque start, high torque continueous duty (good for band saws), high torque start, regualr torge contuiuas duty and so on, and then outside motors weatherproof , and inside motors, etc it takes alot detailed reading to get the right motor, and of course use a usa built motor.

 

here is a extra high torque motor from graingers this will eliminate all starting problems, also a high torque motor will use less electricyt than a regular duty that is overloaded

rm Duty Motor,5 HP,1740,230v,184T,TEFC
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Extra-High Torque Farm Duty Motor, Capacitor-Start, Capacitor-Run, Totally Enclosed Fan-Cooled, 5 HP, 1740 Nameplate RPM, 230 Voltage, 184T NEMA/IEC Frame, Service Factor 1.15, 60 Hz, Base Mounting, Sealed Ball Bearings, Thermal Protection Manual, Full Load Amps 20.5, Ambient 40 C, Rotation CW/CCW, Shaft Dia 1 1/8 In, Shaft Length 2 3/4 In, Insulation Cl*** F
Grainger Item # 1TMV3
Price (ea.) $738.50
Brand DAYTON
Mfr. Model # 1TMV3
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Ship Weight (lbs.) 113.0
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High- and Extra-High-Torque Capacitor-Start Totally Enclosed Fan-Cooled Motors
Features include gasketed conduit box, capacitor cover, and rubber boot over the manual protector reset ****on, sealing motor against weather and contaminants.
Oversized conduit boxes make connections easier. Shaft slinger included. UL Recognized and CSA Certified.
Uses: For conveyors, silo unloaders, barn cleaners, compressors, and manure pumps.
Max. ambient: 40 DegreeC
Thermal protection: manual
Bearings: sealed ball on 56 through 184T frames; shielded on 215T frames
Rotation: CW/CCW
Duty: continuous
Color: green
Extra-High-Torque
With up to 400% starting torque for extremely hard-starting applications, these motors can be counted on to start under full-load conditions.












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