AnsweredAssumed Answered

Conductor size compared to lug size

Question asked by dlavigne1980 on Oct 4, 2019
Latest reply on Oct 6, 2019 by rcramereleceng

Scenario:

There is a 4 bar electrification system for an Overhead Bridge Crane.  The runway is 900 ft long.  The company that designed the electrification system needed to use bar that is rated up to 250amps to obtain a minimal voltage loss at the ends of the runway.  This runway will have a single 5 Ton crane system on it.  The amp draw for this crane is 50amps 460 volts.  

 

What happened:

The circuit for the runway is rated at 60amps.  The wires for the circuit are rated at 60amps.  When terminating the wires onto the electrification the lug for the power feed provided is designed for a wire capable of 250amps.  The hole is much too large for this wire and when setting the wire into the lug the allen head set screw runs out of thread and falls into the opening before even starting to tighten the wire for the 60amp circuit.  i requested we use the 90amp power feeds to have proper termination of this wire.  I was told that i just need to strip more wire back and fold wire onto itself untill i can tighten set screw.  

 

Question:

Is folding conductor to obtain a larger cross sectional area of a conductor allowed?  I looked in my NEC 2011 but could not find anything on this.

 

Reason why 250amp bar was used is because its made out of solid copper and has a lower resistance.

Outcomes