What I found today, Be sure to visually inspect disconnects! scary

[hockeyoligist2]

Got a call that a motor was tripping. I locked it out and went downstairs to check things. Opened the disconnect and said OS! I was going to OHM and meg the motor, the smell made me step back and get my flashlight! I didn't get a pic while it was still in the disconnect. I was 4 story's underground and too lazy to go get my camera. It melted the wire on A phase so I had to pull a short run from the disco to the motor.

 

[hockeyoligist2]

before I am asked....

before I am asked....

The right side knife receptor is missing because I was trying to figure out which screws held it in the box!

 

[hardworkingstiff]

Wow, that really had to be hot.

Thanks for sharing the pic.

 

[mivey]

What was the original heat source? The receptor looks fine. The bottom wire termination looks like it has been hot but maybe not hot enough. Was there a bad connection in the blade?

 

[StephenSDH]

Thanks for the pic.

 

[mivey]

The top connector looks hot enough but I would think the blade would have more discoloration.

 

[hockeyoligist2]

Not sure what happened. No loose connections. The top side was OK, no heat signs. Motor megged OK. "A" phase was melted off at the bottom of the disconnect. When I pulled the wires out to replace them I saw no obvious shortage to ground or phase to phase.

I replaced the disconnect, restarted the motor, amps are good (9 amps all 3 legs on a 14 FLA motor).

 

[cowboyjwc]

I wonder if the receptor was a little loose.

 

[mivey]

I wonder if the receptor was a little loose.

I wondered that but wouldn't you expect more discoloration if it was the culprit? It looks like most of the action was taking place below the area of red plastic. Not sure why the connector up top was so discolored relative to the rest unless it was just a second factor but not the main contributor.

 

[iwire]

I would say the problem started at the pivot.

 

[cadpoint]

Where's the "C" blade recptor ?

Please describe the motor ?

 

[mivey]

Where's the "C" blade recptor ?

See #2 .

 

[mxslick]

What brand was this disconnect?

I agree with Iwire, it failed at the pivot point.

Several years ago I was witness to a very bad arc flash incident, the mounting screws for the disconnect mechanism had rotted away, and when the electrician went to turn it off the whole mechanism slammed against the cover, which exploded. It was the famous "Bulldog" brand.

Since then I have always stood off to one side and not looked at any disconnect when operating it. I do the same when operating breakers too.

 

[cowboyjwc]

I wondered that but wouldn't you expect more discoloration if it was the culprit? It looks like most of the action was taking place below the area of red plastic. Not sure why the connector up top was so discolored relative to the rest unless it was just a second factor but not the main contributor.

That was also my thought about the dicoloration, but after I had posted I started to think about it and I think I agree with Bob, though I've never seen that happen before.

 

[mivey]

That was also my thought about the dicoloration, but after I had posted I started to think about it and I think I agree with Bob, though I've never seen that happen before.

Me either. It is usually the terminal or at the blade contacts

 

[augie47]

I would say the problem started at the pivot.

agree...................

 

[charlietuna]

We have found many disconnects with this same problem where the actual knife controling shaft was melted in half(made of plastic)-- end result -- even though you turn the switch "OFF" two blades never disconnect !!! Always use your tester before servicing !!! And it happens on Square D Equipment !

 

[LarryFine]

Wow, that really had to be hot.

And in more than one way.

 

[hockeyoligist2]

What brand was this disconnect?

.

Square D 60 amp.

 

[weressl]

Got a call that a motor was tripping. I locked it out and went downstairs to check things. Opened the disconnect and said OS! I was going to OHM and meg the motor, the smell made me step back and get my flashlight! I didn't get a pic while it was still in the disconnect. I was 4 story's underground and too lazy to go get my camera. It melted the wire on A phase so I had to pull a short run from the disco to the motor.

Welded pole, happens all the time.

Another fine example of why TBT.

At least this is visible, but we had and occurence within a CB where the welded contacts were invisible. Got the guy knocked on his seat....

SQ made a breaker with inspection windows, but I think never made it prime-time. (EU/IEC market push originaly.)

What is surprising to me though is that the bridge melted. I would expected that to be constructed from thermosetting resin fiberglass reinforced. Surprised that UL let this pass.