UL listing provisions for splicing in manufactured equipment

[georgemsmith]

Gentlemen,

During the commissioning phase of a large gas/oil production platform, a splice made by the contractor was discovered in the internal wire way of a UL listed Motor Control Center. Considering that it was done using inline splices and insulated appropriately, as not to fill the wire way beyond the 75% permitted in other wire way applications, is there anything within either the NEC or the UL listing that would deem this unacceptable? This is a 3 phase/480 volt MCC built to ANSI standards

I personally am against paying an electrical contractor for such work on a new project when it would be much better to have a continuous conductor to the motor, but I have limited resources here in Indonesia to research this. I have found a few references in the NEC that seem to allow this..376.56, 312.8, 430.10 but am concerned that UL has not tested this Siemens Motor Control Center for this purpose.

 

[ramsy]

It seems to me, hiring an experienced infra-red scope analysis for all conductor & terminal temperatures under load, for the entire platform electrical systems, would go much further in proving the safety of this installation or that splice, under normal operating conditions. A simple impedance test, under load, could also reveal the load carrying capacity or heat potential of that spliced circuit.

While working a short stint with Southern Calif. Edison (SCE) in 2005, I did see a 200Amp knucle splice for a feeder that was too short to reach the panel. We removed this lug-nut splice, dropped it on the ground for the inside wireman to retrieve, crimped it on the spot with a proper sized Burndy cylinder, then installed the service meter. Our service truck was equiped with all sizes of these crimps, and they were used regularly in similar fashion.

Don't ask me how this Burndy cyclinder accomplished, both mechanical and load carrying integrety for 200A, or why the guy I worked with was doing this hot, but after helping these outside lineman crews in thunder and lightning for a few storms, I decided it was time to go back inside.

 

[georgemsmith]

Roger,

Thanks for your reply. Our RCM program does employ FLIR Thermography on a yearly basis for all of our electrical equipment. Now that we know that this splice is there, we will monitor it if we don't replace the cable run entirely.

My point is that for new construction, this is just bad practice. The reason quoted by the contractor is that the terminations at the breaker were not rated for the conductor size. Of course, there are pin terminations available which are listed for this purpose and would have been far more acceptable than a splice in the wire way.

 

[ramsy]

George, I've got another idea. If the breaker listing will accomodate the larger wire I agree it could be directly connected, since NEC code permits oversized conductors on terminations if within product / terminal listings.

However, if the smaller wire is the max listing limit, that larger cable run should not be replaced if needed for voltage drop or extra load considerations along the way. Using wirenuts to splice wire reductions to devices is common for inside work, although usually found behind walls.

While the location of your control center splice could be moved, IMO if the breaker requires the reduction the splice should remain in the open, accessable to infra-red (FLIR) inspection and maintenance.

OTOH, the pin termination you mentioned sounds interesting. Would that be a 14 to 8 AWG pin with the reciprocal end for the breaker / terminal, oposite the receptacle end for crimping to conductors?

 

[jim dungar]

No, there is nothing in the NEC that would prohibit this installation., as long as the cross sectional area of the wireway is adequate. Neither Seimens nor UL would probably object either.