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Joined: Mar 2005
Posts: 236
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OK guy's I am working 4 A.M to noon -thirty and am too tired to look this one up, however it should be an easy one for you guy's.

Question: spider boxes feeding office furniture with several circuits and several whips (3/4 inch flex 8-12 feet long)must each whip contain a green grounding conductor?

I feel (IMHO) that one would suffice the code intention of bonding with conductor rather then a whip. The number of whips is immaterial, because we have established a fault path, which is the intention of the code.

I realize i am sticking my head out there with my "Humble Opinion" but, like I said I am tired.

Thanks in advance as always,
H20

2017 / 2014 NEC & Related Books and Study Guides
Joined: Jun 2004
Posts: 1,273
T
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The only manufactured office furniture hook-ups I've ever encountered needed a ground in each whip and multiple neutrals -- typically oversized, too.

The term 'spider boxes' is only ever used out my way to describe temp power boxes used during construction.

Normally office furniture is fed from 'floor boxes.' They might be 'poke-thrus' or 'mud boxes.' Either way custom 'activations' are purchased to effect a professional transition to the furniture.

The EGC is needed because in an office setting a decent ground is required by common equipment.

Not uncommonly, even Isolated Grounds are called out in the plans.

Cheers.


Tesla
Joined: Mar 2005
Posts: 236
Member
Thanks Tesla,
yes I understand about the decent ground. My question is more about the redundant grounds, you see each whip (3 qty) from my jbox to the spider box has a EGC in the flex with the branch circuits, wouldn't 1 qty EGC suffice the code for bonding the spider box? Or does the code require all 3 whips to have a grounding (earthing , I believe is the new language)conductor?

Thanks again,
H20

Joined: Jul 2004
Posts: 9,662
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G
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You need a ground in any FMC whip over 6 feet 250.18 and if "flexibility is required" you need a ground no matter how long it is 348.60 but this installation is more troubling when you look at 348.30 and supporting/securing that FMC. I have a little thing about this because of the number of times I have pulled a floor tile under a computer room floor and seen the FMC about 3" from the connector and looking at the THHN. Joe T may even have some of those pictures that I took. They ran in IAEI magazine at least twice.
I would not run FMC anywhere that it will really be moved around much without clamping it beyond the box connector.


Greg Fretwell

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