Critical Failure

[mooreaaryan]

For an interconnected solar system. I have 5 parallel feeders from the farm to the disconnect ran about 525ft . The system is 1200amp we used 5 -500 aluminum conductors and combined them using IPLD-500-10 “Polaris” lug and stepped out to the disco with 4-400 coppers to the disconnect. This weekend the Polaris connectors failed and the phase an and phase b made contact faulting the system.
We have torqued tested the Polaris lugs and the torque value is 450in/lbs and we didn’t find an issue. What else could have caused this issue?
The only conductors showing damage are the aluminum conductors

 

[augie47]

Were the Cu & AL conductors staggered between ports ?

 

[mooreaaryan]

No sir. Is it best practice to stagger between ports?

 

[LarryFine]

No sir. Is it best practice to stagger between ports?

Absolutely. That way the cross-section of the bar doesn't have to carry the total current in one place.

Staggering or alternating conductors spreads the current out among the sections between the ports.

Like interlacing your fingers. I can't ind a better pic. Like this, continue the pattern in, out, in, out, etc.

 

[don_resqcapt19]

If the staggering of the conductors is necessary, it should be in the installation instructions for the connector. I did not see that in the instructions for this part number, but have seen it instructions for other power distribution blocks.
However, I agree with Larry that it is a good practice.

 

[mooreaaryan]

No we had them stacked. Al one side CU the other smh

 

[augie47]

NSI publication....

https://images.thdstatic.com/catalog/pdfImages/bd/bd46a4d8-8ee3-45b9-8005-1be2af28781b.pdf

"laboratory tests have shown that the
connector will run cooler if the load is “distributed”.
The recommendation is to stagger the line and load
conductors (line-load-line-load-line-load) throughout
the wire connector."