mc cable installation.

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cmreschke

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hello there everyone. new to the forum been reading for about a month enjoy the site tremendously. ok so im running a big box store remodel, we are installing the cash register power poles each power pole is fed with two circuits. circuit 1 is from panel A, circuit 2 is from panel B. panel a is 120/240 single phase (u.p.s. protected) panel b is 120/208 three phase (normal panel) both circuits 120 volt 20 amp. panels are fed from different locations and different transformers which eventually come from the same m.d.p. the factory supplied 3/8s flex whips coming from the power pole go to the same 4 square box and terminate to the box using a double mc connector locknut set screw type. the arguement is with one of my journeymen whom claims that that is a violation because the are fed from two seperate power sources. i say not a violation. i told him to show me (its a test) his reasoning is sound but i dont see a problem with it how bout you fellows. thanks for the unobjective oppinion.

Chris Reschke
Master Electrician
Memphis, Michigan (40 miles north of the motor city)
 
I agree probably not a violation I didn't look.

But you didn't mention anything about separating the two sources with a divider or anything.

What if you had a fault in this 4" square box and the two sources where touching.

Now you have a power outage and the UPS system kicks in powering its emergency sources
would this not possibly feed power back on the normal system and maybe be a shock hazard to the utility workers?

It would be a no no for me.
 
ronaldrc said:
I agree probably not a violation I didn't look.
Click to expand...

It is not.

But you didn't mention anything about separating the two sources with a divider or anything.
Click to expand...

There is no requirement to do so.

What if you had a fault in this 4" square box and the two sources where touching.
Click to expand...

I don't know, what would happen if there was one source in the box and it was touching the box?

Now you have a power outage and the UPS system kicks in powering its emergency sources would this not possibly feed power back on the normal system and maybe be a shock hazard to the utility workers?
Click to expand...

How is this different from both 'normal' and 'emergency' power sharing a common junction box supplying an exit light?
 
Bob

Its not in most jobs I worked on with emeregency systems the only place I can recall
of them being in the same enclosure was in the Emergency lights.All the Emergency power was in separate Red cover recpts.

He ask for a NEC reason I don't know of one off the top of my head but I just think it should stay separated as much as possible, I wouldn't want to cause a safety hazard just because its the easy way to do it.

This would be no less dangerous than putting 240 on a 277 volt threeway switch
that most thought would be so dangerous.
 
iwire said:
2008.

In the 2005 I think the rule is just in another location.
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I believe it is the same section in the 2005 as well, From the 2005 NEC


(C) Ungrounded Conductors Where the premises wiring system has branch circuits supplied from more than one nominal voltage system, each ungrounded conductor of a branch circuit, where accessible, shall be identified by system. The means of identification shall be permitted to be by separate color coding, marking tape, tagging, or other approved means and shall be permanently posted at each branch-circuit panelboard or similar branch-circuit distribution equipment.


Changed From 2002

?210.5(C): Added new requirement that each ungrounded branch-circuit conductor be identified by where there is more than one nominal voltage system on the premises and that the means of identification be posted at each branch-circuit panelboard or similar distribution equipment
 
The 2002 code required identification of the ungrounded conductors as to both phase and system, but the rule only applied to the ungrounded conductors of multiwire circuits, in buildings with more than one voltage system. 210.4(D)

In the 2005 code they expanded the rule to apply to all ungrounded conductors in buildings with more than one voltage system, but you were only required to identify by system. 210.5(C)

In the 2008 code the requirement was changed to require identification by both phase and system for the ungrounded conductors in buildings with more than one voltage system. 210.5(C)
 
ronaldrc said:
Hello Bob

I would think a UPS would be an Emergency system.
Click to expand...

No, that would be optional standby in Article 702.:)

As much as the store may feel the cash registrars power is an emergency the NEC does not.

See 700.1 :)


......... Emergency systems are those systems legally required and classed as emergency by municipal, state, federal, or other codes, or by any governmental agency having jurisdiction....

... intended to supply, distribute, and control power and illumination essential for safety to human life.....
 
Bob

Even if you are right about it not being an Emergency system??

The physic still are the same it would still be a safety hazard.

What if some Electrician come and did maintenance on one of those boxes and tied the neutrals together. Would this not paralell the neutrals.

I made a mistake this morning when I got up.
Hu that electrician could very well be me. :confused:

If the main breaker was kicked and the ungrounded conductors where touching
would it not creat a shock hazard?

I'm suggesting at the very least a divider barrier is needed.:)
 
thanks for all the replies and btw it is not emergency power it is just back up battery power so that they can continue sales if they lose power (which seems to be frequent)
 
ronaldrc said:
Bob

Even if you are right about it not being an Emergency system??

The physic still are the same it would still be a safety hazard.

What if some Electrician come and did maintenance on one of those boxes and tied the neutrals together. Would this not paralell the neutrals.

I made a mistake this morning when I got up.
Hu that electrician could very well be me. :confused:

If the main breaker was kicked and the ungrounded conductors where touching
would it not creat a shock hazard?

I'm suggesting at the very least a divider barrier is needed.:)
Click to expand...

I'm with Bob. Not a violation.

But for safety purposes, I'd use my label maker and make a nice, bright yellow label for the cover that would read something like "Caution: electrical feed from 2 sources" or something like it, to CYB.
 
Considering I see this type of installation all the time and it does not strike me as unusual or unsafe at all I see no need for barriers or any special measures.

We do as a rule label all j-boxes with the panel and circuit numbers.:)
 
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