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Air compressor contactor/wiring problem. Need help please!

Ltk

Plastic
Joined
Sep 24, 2021
I purchased a 10 HP, 3-phase Ingersoll T30 the other day that was unwired. I have attempted to wire the Furnas Size 2 motor starter and pressure switch back up to the best of my ability. I have 3-phase power coming from my RPC (American Rotary AD20) and have ran a circuit for the compressor (10AWG, 60A).

I am having an issue starting the compressor. I'm getting good power to L1,L2,L3. When I turn the switch to 'ON' the contactors chatter very loudly. I can manually push the contactors in and the motor starts and spins just fine. When I release, the contactors do not hold and the motor powers down..

I will upload pictures to this thread to help with assisting me, thanks!

I have a 10HP lathe running off of this RPC also so I do not believe that is the problem.

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13engines

Hot Rolled
Joined
Jun 30, 2015
Location
Saint Paul
Make sure your two plain jane 1ph wires go to the coil and all other parts of the starter and pressure control circuits. The manufactured leg of your RPC should only go to the motor leads and nowhere else.

60 amps on 10 awg wire? Try 30.

Ha... and I 2nd everything tbirds said. That is one crusty contactor. :-)
 

tbirds

Aluminum
Joined
Mar 8, 2008
Location
Montreal, Canada.
That's quite a coincidence you should post about the exact same issue I had last week with my 50 year old lathe; the forward contactor was doing the same as yours; the contacts were badly pitted causing arcing, chatter and tripping the overloads in the switch box. That contactor was replaced with a modern new one, and that fixed it.
After this the reverse contactor started doing the same thing 5 times out of 10, so I dismantled the old contactors, polished all the contacts with sand paper, and replaced them one by one in the reverse contactor. That was enough to cure the issue for now..
Looking at your picture, that contactor looks like it's got some age to it; given my experience, I would suspect it. By polishing the contacts, it made enough of a good contact to hold the coil ...
Cheers
 

CITIZEN F16

Titanium
Joined
May 2, 2021
Agree with everything said, for real 60 amps you better run #6 wire. Air compressor motors are often heavily loaded and draw full HP and sometimes a little more, so you cannot get away with undersized wire like you could run a phase converter idler motor off of. That being said I doubt a 10 HP compressor motor would draw much over 35 amps. Furnas Electric was no more about 30 years ago if my memory serves me correctly, so that contactor is high mileage as others have alluded to. Chatter is either bad contacts or a weak coil. The sandpaper trick might work, no harm in trying. If it was me I would just replace the contactor, I scored a few NOS ones off of E-bay when I rebuilt my phase converter. You could check there if you have more time than money.

I would get a 40 amp contactor and run some #8 wire and call it a day.
 

Ltk

Plastic
Joined
Sep 24, 2021
Make sure your two plain jane 1ph wires go to the coil and all other parts of the starter and pressure control circuits. The manufactured leg of your RPC should only go to the motor leads and nowhere else.

60 amps on 10 awg wire? Try 30.

Ha... and I 2nd everything tbirds said. That is one crusty contactor. :-)

I'm not 100% sure that I have it all wired correctly in the starter/pressure switch. If I didn't would the motor still start when the contactors were manually pushed on?

That's quite a coincidence you should post about the exact same issue I had last week with my 50 year old lathe; the forward contactor was doing the same as yours; the contacts were badly pitted causing arcing, chatter and tripping the overloads in the switch box. That contactor was replaced with a modern new one, and that fixed it.
After this the reverse contactor started doing the same thing 5 times out of 10, so I dismantled the old contactors, polished all the contacts with sand paper, and replaced them one by one in the reverse contactor. That was enough to cure the issue for now..
Looking at your picture, that contactor looks like it's got some age to it; given my experience, I would suspect it. By polishing the contacts, it made enough of a good contact to hold the coil ...
Cheers

Thanks, I will dismantle it and polish them all up and give it a shot before I do anything more expensive! It's a 1977 model so I assume thats the age of the motor starter also.

Agree with everything said, for real 60 amps you better run #6 wire. Air compressor motors are often heavily loaded and draw full HP and sometimes a little more, so you cannot get away with undersized wire like you could run a phase converter idler motor off of. That being said I doubt a 10 HP compressor motor would draw much over 35 amps. Furnas Electric was no more about 30 years ago if my memory serves me correctly, so that contactor is high mileage as others have alluded to. Chatter is either bad contacts or a weak coil. The sandpaper trick might work, no harm in trying. If it was me I would just replace the contactor, I scored a few NOS ones off of E-bay when I rebuilt my phase converter. You could check there if you have more time than money.

I would get a 40 amp contactor and run some #8 wire and call it a day.

I will start looking for new contactors for this, is it necessary to buy the entire setup or just the contactors themselves? And I will switch to #8 wire to make sure everything is good to go. How do I know if the coil is bad? I measured 165v at one point, and all points on the coil measured 150 ohms
 

CITIZEN F16

Titanium
Joined
May 2, 2021
002.jpg

Should be similar except that is 240 single phase. Sorry about the colors of the wire I got the thing used and just swapped out the contactor. Coil resistance on mine is 183 ohms, your coil should have survived that 165 volts but get that off of there.

Got any questions on what wires go where just ask I will be in and out all day.
 

Ltk

Plastic
Joined
Sep 24, 2021
View attachment 343726

Should be similar except that is 240 single phase. Sorry about the colors of the wire I got the thing used and just swapped out the contactor. Coil resistance on mine is 183 ohms, your coil should have survived that 165 volts but get that off of there.

Got any questions on what wires go where just ask I will be in and out all day.

I switched the wire from the generated leg to the other. I also polished all of the contactors very nicely and instead of the chattering, I'm getting loud buzzing now.

In my 2nd picture, the yellow wires are running to the pressure switch. So the start/stop button has 1 lead coming from pressure switch, 1 lead coming from terminal L1. The coil is wired for low voltage, I'm actually getting no voltage to the coil now?
 

Ltk

Plastic
Joined
Sep 24, 2021
Sounds like you have the manufactured leg powering the coil, that is incorrect. See post 5 as that can also be a source of chatter.

I polished all of the contactors very nicely, reassembled them and now I'm getting a loud buzzing. Still able to manually engage the contactors and spin the motor but it is releasing when I let go instead of holding
 

CITIZEN F16

Titanium
Joined
May 2, 2021
I polished all of the contactors very nicely, reassembled them and now I'm getting a loud buzzing. Still able to manually engage the contactors and spin the motor but it is releasing when I let go instead of holding

Buzzing is usually low voltage to the coil, if it is the contactor doing it.
 

Ltk

Plastic
Joined
Sep 24, 2021
The coil was reading 165v, its now reading 5v. Is it hooked up to the wrong spots? In picture 2 on my first post: one lead of the coil goes to L1, the other to the start switch, the other to the magnetic switch (3).
 

CITIZEN F16

Titanium
Joined
May 2, 2021
The coil was reading 165v, its now reading 5v. Is it hooked up to the wrong spots? In picture 2 on my first post: one lead of the coil goes to L1, the other to the start switch, the other to the magnetic switch (3).

I have a bad neck from an old football injury, could you repost pic #2 orientated correctly? I don't like tilting my head. I tried rotating it but my software won't cooperate. I am curious about the interlock. Strange you came up with 5 volts, is there a hot to ground somewhere or a bad ground some where?
 

Ltk

Plastic
Joined
Sep 24, 2021
I have a bad neck from an old football injury, could you repost pic #2 orientated correctly? I don't like tilting my head. I tried rotating it but my software won't cooperate. I am curious about the interlock. Strange you came up with 5 volts, is there a hot to ground somewhere or a bad ground some where?

Sorry about that, not sure why it was rotated. I'll upload it a different way. I'm also going to take a video and attempt to upload it to possibly show how I have this wired up. It's actually not grounded at all, should I have a ground going from somewhere on the starter? If so, where?
 

CITIZEN F16

Titanium
Joined
May 2, 2021
Sorry about that, not sure why it was rotated. I'll upload it a different way. I'm also going to take a video and attempt to upload it to possibly show how I have this wired up. It's actually not grounded at all, should I have a ground going from somewhere on the starter? If so, where?

How are you making 120v for the coil on the low voltage setting with out a ground or neutral? You did say you are running this off of 3 phase, correct? You will have to excuse me, I have been battling a concussion lately so my memory can be sporadic. Also even when I have a clear head it takes a little time to re-acclimate myself to things I have not done in a while, I think that comes from age. I think I replaced that air compressor contactor a dozen years ago. I scored a screaming deal on some NOS Furnas contactors on E-bay 15 years or so ago. I think they are finally all gone. Until I see another picture I will venture a guess the coil is not hooked up correctly, but so far all components could be ok.
 

dalmatiangirl61

Diamond
Joined
Jan 31, 2011
Location
BFE Nevada/San Marcos Tx
The coil was reading 165v, its now reading 5v. Is it hooked up to the wrong spots? In picture 2 on my first post: one lead of the coil goes to L1, the other to the start switch, the other to the magnetic switch (3).

The contacts are the electrical connections that make/break a connection. The poles of the electromagnet are what I was referring to, I was on first cup of coffee.....

Having a hard time understanding how you have it wired, pics are nice but its hard to follow the wires and know whats what, maybe a quick drawn out schematic would help. According to code your manufactured leg should be clearly identified throughout the system, not only does it keep the man happy, it also keeps you from running it to control circuits:D. If you are only getting 5v to the coil, something is wrong.
 

Ltk

Plastic
Joined
Sep 24, 2021
How are you making 120v for the coil on the low voltage setting with out a ground or neutral? You did say you are running this off of 3 phase, correct? You will have to excuse me, I have been battling a concussion lately so my memory can be sporadic.

I’m not reading any volts across the coil at all. Resistance is there between terminals 1 and 4, resistance is 0 between 1 and 2; 3 and 4

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CITIZEN F16

Titanium
Joined
May 2, 2021
What are the coil jumpers set to voltage wise, I cannot tell from the pictures. The wiring is blocking the jumper setting. I have issues watching videos due to a slow internet connection out in the sticks. Take a few pictures further back. Also I hope whatever crumbs are in that box aren't nesting material for mice or rats, they like eating wires.
 








 
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