Burnt A phase on disconnect

[Dfw high voltage]

I can’t publish any images but ..
Hey there our team did an infrared inspection today and we recently found a burnt Line side A phase 250mcm aluminum conductor on a 400A 480V 3Phase Non fusible Disconnect which fed from a 225A Eaton HFD 65k 3 pole breaker which the disconnect is used to feed a kaeser DSD 125 compressor.

Disconnect line side 250mcm alu
Disconnect load side 4/0 cu

Name plate shows 480v 3 phase 125hp
Unit APC=186
Motor APC=170

We also noted that the mechanical lugs where where oversized for the wire previous installer used 300mcm-750 mcm lugs and was barely grabbing the wire and I’m not sure if that could be the reason loose connection .

Did the previous installer provide the appropriate ocpd for the compressor and feeder wire for this usage

Thank you for your time

 

[Eddie702]

The wire size of both the copper and aluminum conductors and the circuit breaker appear correct to me.

 

[ptonsparky]

Poor connection. Improperly torqued. You got it.

 

[JoeStillman]

...
We also noted that the mechanical lugs where where oversized for the wire previous installer used 300mcm-750 mcm lugs and was barely grabbing the wire and I’m not sure if that could be the reason loose connection .

That's a Bingo!

 

[Dfw high voltage]

Thank you all, we inspected safely and it sure was a loose connection all 3 phases on the line side were loose replaced lugs to appropriate size and added cold shrink on burnt A phase wire for temporary until client decides what he will like to do next.

Poor connection. Improperly torqued. You got it.

The wire size of both the copper and aluminum conductors and the circuit breaker appear correct to me.

That's a Bingo!