ECN Forum Forums General Topics of the Trade General Discussion Area 50 amp breaker on 1/0 conductors

I work in the maintenance department of a mail processing plant. The plant operates numerous hi-tech sorting machines utilizing computer and electronic technology that boggles the mind.

The manufacturer of a particular piece of equipment has sent out a national maintenance order requiring that all of these machines nationwide be protected by a 50 amp breaker. So I have been instructed to swap out the current 80 amp breaker with a 50 amp breaker which was shipped to us from our national maintenance technical center. This special breaker is simply a Square D, QO, 50 amp 3 phase HACR rated breaker wich fits our particular panel.

The problem is that the original specifications for this machine required that 1/0 conductors be pulled for the equipment power with a full sized neutral and ground. The 50 amp breaker will not accommodate the 1/0 conductors. The engineers at the national maintenance center have instructed us to install a junction box at the panel and splice the 1/0 conductors with #2awg conductors using split bolt connectors, then connect the 50 amp breaker to the #2 conductors.

The machine is also protected by fuses and breakers at its disconnect panel.

This makes no sense to me. My questions are how does this affect voltage drop? And is there another better way to provide 50 amp over-current protection to 1/0 conductors?

My personal opinion is that the 80 amp breaker is adequate to protect the conductors and the machine, especially given the OCP devices on the equipment. What do you all say?

Sorry this is so long!

I tend to agree with you. If the machine has it's own protection, the upstream protection could be anything.

As far as Voltage Drop the larger (1/0) conductors are a plus.

The J box and splice sounds like the best way to accomplish this so that is not a problem.

Now, even though you and I agree, it doesn't hold much weight, the manufacturer has found this neccessry for some valid reason and to maintain warranty and or safety (more important) they say you must do it.

Roger

One of the magazines I have has an ad for "ReduceR" connectors that are for your application. Cable reducing adaptor plugs...used to terminate copper conductors where oversized cable is used to compensate for voltage drop.For sizes 1/0 to 1000mcm

 
Suggested components may be:

www.fciconnect.com/pdffiles/brochures/Section_C_2003MC-Compression.pdf

TYPE YE-P “HYPLUG” FOR COPPER CONDUCTOR page 115 are likely not suitable for QO-breaker terminals.

TYPE YH H-TAP COPPER “CRIMPIT” page 107 with ~4AWG-stranded cable “pigtail”/jumper may permit a compact reducing splice.

Hydraulic tooling required for either.

N.B., physically larger “industrial E/F-frame” 15-150 ampere molded-case circuit breakers are routinely available with terminals for 1/0AWG conductors.




[This message has been edited by Bjarney (edited 08-28-2004).]