Compressor Magnetic Starter meltdown

[Gaffer]

I have a Husky Pro, 7.5 HP, 230V 1PH, 80 gallon air compressor. I purchased it used a couple of years ago. It had meltdown before I bought it, but they fixed it and I've had no issues until tonight. One of the feeds melted down, and what brought it to my attention was that it sounded like the air line at the compressor blew because it was exhausting air at a furious rate. I couldn't find a blown line, but noticed one of the 115v feeds lines was smoking at the connector. I figure it's time for a new one but am concerned why it didn't trip something to interrupt it. I shopped replacements and found prices range from about $170 hundreds more. Mine is a Square D 8911DPS042V09. In the photo, to right, you can see the melting damage from the previous failure. To the left of it is my meltdown. I appreciate any and all advice. Thanks!

 

[benmychree]

What was the full load amps of the motor? I suspect that the contactor was undersized, maybe the incoming wiring as well.

 

[Nutfarmer]

Could have been a loose or corroded wire where it burnt. Below the contactor are the heater strips so it had over load protection. Think about how many times the compressors cycles on and off. It may have just wore out.

 

[mksj]

Agree with above, it may have been corrosion or loose contacts.
Might check this one out, $135 with shipping.

SQUARE D ELECTRIC MOTOR STARTER 8911DPSG42V09 7.5HP 40AMP 208-230V 1-PHASE | eBay

PHASE: SINGLE (2 POLE).

www.ebay.com

or 3 phase and run a jumper from T2 to L3 for single phase

SQUARE D ELECTRIC MAGNETIC MOTOR STARTER CONTROL 7.5HP 230V 3PH 8911DPSG23V09 | eBay

A motor starter is for the purpose of protecting a motor that has no thermal overload protection in the motor itself. WHAT IS A MAGNETIC STARTER & WHAT PURPOSE DOES IT SERVE??. THIS STARTER IS DESIGNED TO BE USED WITH 7.5HP 3PHASE 208-230 VOLT ELECTRIC MOTORS.

www.ebay.com

 

[Bi11Hudson]

Looks like it failed before and was repaired. If that is indeed the case, I would speculate the starter is too light. That center lug top was obviously loose. Looking to the right, it has been loose before and been jerry rigged once already.

.

 

[Reddinr]

You could also have a look at Automation Direct and replace the contactor and overload and keep the enclosure. Likely cheaper. Have a look at SC-E2S-220VAC contactor with a TK-E2-4200 overload. About $114 I think. The contactor is three poles but you only need to use two. Anyway, worth a look to be sure it is a fit. Based on what is on the contactor you have it looks like the overload is 40 Amps and the contactor coil is 220 VAC. That is what I based the part numbers on. Check the dimensions to be sure everything fits comfortably in your box. You might also find something on Ebay even cheaper.

I agree with the loose wire theory or maybe burned contacts. Either one would not trip a breaker. It would just heat up.

 

[markba633csi]

Undersized wiring and poor crimps, most likely.
7.5 HP that's a bunch of amps
-M

 

[Reddinr]

I think a 7.5HP motor is about 25 or so amps continuous at 230V. There would be some start-up current for a few seconds above that. If the CB feeding the thing is 40A, the wiring should be at least 8 AWG. If it is fed with a 30A breaker then 10 AWG would be safe enough. However, a 40A breaker and larger wire may be more appropriate to deal with the start-up currents. A 30A breaker might be just big enough to ride through the start-ups though and cool down between cycles. If the wires were #10, or even undersized at #12 that is unlikely to be the root cause. Just a loose connection of some sort or charred contacts. Those definite purpose contactors are on the quality low-end of contactors in the grand scheme of all contactors. If it were me, I might up-size the wiring/breaker. Sorry for getting off topic. You just needed a new motor starter!

 

[pdentrem]

On the ones that I had to replace at work, it is either a slightly loose at the terminal, undersized and the points burned out. I had one that one of the three contacts was welded together, but it had seen a long service life. Due to the fuse link still intact, it was a loose connection. Crimped wire ends are suggested.
Just like the old aluminum wiring in the houses, the wire becomes loose over time and heats into a fire. The corrosion that aluminum wire has occurs over time is also an issue. There is a fix for that.
Pierre

 

[Gaffer]

I appreciate the responses. The owners manual called or 10AWG and that is what I ran directly from my panel. I believe the old unit is worn out and likely not treated well in the past. The contacts look bad and the one shows tremendous heat. Should I replace the pressure switch while I'm at it, or is that not an issue?