Slave for life!!!

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benaround

Senior Member
Location
Arizona
Here is the layout,

Voltage: all the common voltages up to 480/277

Amperes: as in panel size 100a-400a and larger, MCB or MLO

Here's the deal, a lighting contactor is nippled to any of the above, let's

say six circuitsare controlled. The Inspectors are requiring us to either

loop 10' of the branch circuit conductors in the panel or run 10' of pipe

to a j-box and then back down to the LCC instead of using a nipple.

The Inspectors can't really explain to me why, but they are just doing

their job. It has something to do with the circuit needs enough resistance

to trip the c.b.?

This has been bugging me for awhile, If anyone can explain this to me,

I be your slave for life!!
 
Ben
The Inspectors can't really explain to me why, but they are just doing their job. It has something to do with the circuit needs enough resistance to trip the c.b.
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I think that may be an oxymoron or maybe the inspector is one.

I would like to see the code section that dictates the extra 10 Ft. In fact the oposite is true. The more resistance in the circuit the less amperage and more time for the breaker to operate. He may be thinking that you need to lower the fault current to a safer value for the breaker by increasing the circuit resistance..
 
Never heard that one before. If that has any truth to it, then the 2 lighting contactors I just nippled off of my panel would be wrong.
 
Peteo,

You the man!!! that is exactly what the Inspectors could not explain to

me. I just printed it so I can show others what the heck has been going

on.

Again thank you.

Frank

ps about that save the wife thing=====
 
Does anybody else see the enormous gaping hole in the logic on this, or am I about to swallow fourteen pounds of crow, beaks and all?

Where the #^%# did "10 feet" come from?

Regardless of the inspector's theory (which I do solemnly bow down to, and Peteo for popping up with that), you can't just pull a number out of a hat!

Look closely at the PDF Peteo linked to. Look at figure 2. It has 4000 extra amps of fault current available and the run is 25 feet long!

Why not fail the contactor? Why prescribe a meaningless wire run?
 
georgestolz said:
Does anybody else see the enormous gaping hole in the logic on this, or am I about to swallow fourteen pounds of crow, beaks and all?

Where the #^%# did "10 feet" come from?
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Go get your crows. I'm not sure why nobody else replied.

The basic idea is more wire will reduce the fault current available at the end of the wire, to meet the SCCR. You can calculate the length required (it will be longer the more fault current at the source and the larger the conductor for example). For only 10 feet it must have only exceeded the SCCR by a little.

I'm curious about 110.10 which is the requirement. I'm no expert on this, and since it says items applied within the listing requirements meet 110.10, I took that to mean I didn't have to think about complicated calculations. What would be the listing requirement for this case? Seems like it is the SCCR. Then it seems like the "Listed products applied in accordance with their listing meet this requirement" doesn't really mean much.

The other thing, what is special about this lighting contactor that has this SCCR. Wouldn't everything have a limit (like a simple light switch)?
 
This inspector seems to have made a valiant effort to learn something that may help. The problem with this is that he does not understand it, so he is applying it incorrectly. That is where the phrase " a little knowledge can be dangerous" has evolved from.

This is pretty sad....
 
George we run into this once in a while now.

The pad mount transformer suppling a building will be intentionally placed some distance away from the service gear to bring the fault current down.
 
To All,

Thanks to all who posted. Now to clear up a couple of things.


First, The Inspectors in this area are required to inspect the whole

building,ie, structural,plumbing,concrete,electrical,drywall, etc. and

that's a lot to have to know about. This is not just one person that I

was refering to in my OP, it's come from 3 different jurisdictions and

all with the same 10' thing.

To the best of my knowledge this has come down to them from a higher

than local level? Hence the statement 'they were just doing there job'

I hope that makes more sense now.


Second, thanks to this Forum I'll have the heads up that I didn't have

two days ago, I would have been a wiser Electrician if the Forum was

around about 1967, when I started this Trade but Noooooo.
 
iwire said:
George we run into this once in a while now.

The pad mount transformer suppling a building will be intentionally placed some distance away from the service gear to bring the fault current down.
Click to expand...
Is this distance determined by the engineer, or the guy driving the burrito truck? :D
 
What I read was,

"or run 10' of pipe to a j-box and then back down to the LCC"

which looked like a typical factory 20 foot series rating out of a panel. No mystery.

Dad lives in Surprise, a suburb of Phoenix. Like L.A., the residential inspectors there are expected to take on the entire job. One of dad's neighbors built a guest house last year, common in their subdivision. When the inspector came to visit for the final, the next door neighbor showed up with a tape measure. They found that the slab extended two inches across the property line. That poor inspector was 'permitted' to pay for a demo crew along with the cost of rebuilding. Have a little heart...
 
georgestolz said:
iwire said:
George we run into this once in a while now.

The pad mount transformer suppling a building will be intentionally placed some distance away from the service gear to bring the fault current down.
Click to expand...
Is this distance determined by the engineer, or the guy driving the burrito truck? :D
Click to expand...

It would be determined by the engineer, I am not sure if he drives a burrito truck on the side.
 
Frank, dam you're getting old. :D


Second, thanks to this Forum I'll have the heads up that I didn't have

two days ago, I would have been a wiser Electrician if the Forum was

around about 1967, when I started this Trade but Noooooo
Click to expand...

H***, I'd be properly educated and know a little something if that were the case, instead of still learning.

I started apprenticeship in '60.
 
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