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#189570 - 10/17/09 02:58 PM Bonding of a hanghole enclosure lid
Niko Offline
Member

Registered: 08/17/06
Posts: 358
Loc: Campbell, CA
If a handhole enclosure is being used as a pull box only without any splices, does the metal lid have to be bonded to the EGC that is available in the handhole enclosure?

250.148 allows it not be connected, however, 314.30(D) refers to 250.96(a) which basically says you need it.

Thank you for your comments.
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#189571 - 10/17/09 03:59 PM Re: Bonding of a hanghole enclosure lid [Re: Niko]
Yoopersup Offline
Member

Registered: 03/04/03
Posts: 826
Loc: Michigan
I think 250.148 is meant mainly for metal boxes, (250.148D). Most if not all handholes are not metal ( covers sometimes are).
314.30 (D) clearly states handhole cover if metal must be bonded . Thats my opinion.
Yoopersup

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#189577 - 10/17/09 07:47 PM Re: Bonding of a hanghole enclosure lid [Re: Yoopersup]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5300
Loc: Blue Collar Country
Considering the recent spate of electrocutions - mostly of pets - involving energized handhole covers, I think it's time to consider this a 'must do.'

Especially since you use the metal covers when you need a 'traffic rated' cover.

If it's any help, these covers invariably have some angle iron on them - a convenient place to bond. Or, the metal is plenty thick enough to support screw threads. (Just don't use long Teks screws; you don't want to go into the flat tire manufacturing business!)

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#189602 - 10/19/09 07:52 AM Re: Bonding of a hanghole enclosure lid [Re: renosteinke]
electure Offline

Member

Registered: 12/24/00
Posts: 4225
Loc: Fullerton, CA USA

Reno,
I know about your theories on sheet metal screws (or teks) for bonding purposes, but the NEC doesn't share your views.

The NEC says "no sheet metal screws".

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#189603 - 10/19/09 08:46 AM Re: Bonding of a hanghole enclosure lid [Re: electure]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5300
Loc: Blue Collar Country
I believe that you are referring to 250.8. I made the appropriate proposals, and in 2008 the phrase you quote was removed, and the section rewritten. It's not perfect, but I think you can include Teks screws under the permitted 'thread forming machine screws that engage not less than two threads in the enclosure.' 250.8(A)(6)

250.8(A)(5) references machine screws as well; please note that I said the metal would be thick enough to support screw threads. That is, to use a tap to cut threads, then use a machine screw. While not mentioned in 250.8, I think the use of ordinary machine screws carries with it a need to consider the appropriate washers, or loc-tite, to prevent the fastener from coming loose. This is not an issue where the fastener makes its' own threads.

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#189605 - 10/19/09 11:10 AM Re: Bonding of a hanghole enclosure lid [Re: renosteinke]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
I suppose it is different in dry places but everywhere I have lived, a steel screw in a steel cover will rust off in a few years and you won't get it out in a month.
You could probably get by with a stainless nut and bolt.
I don't see a lot of hand holes but the ones I have seen with metal covers, the cover was not bonded. I do see how it could become a concern though if the splices were not shoved down into the hole or properly insulated.
I would consider this an underground (underwater in most cases) location and want to see a splice suitable for that.
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#189606 - 10/19/09 01:12 PM Re: Bonding of a hanghole enclosure lid [Re: gfretwell]
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5300
Loc: Blue Collar Country
To expand on Niko's question .... let's assume a steel cover that rests in a steel frame when the cover is closed.

Would bonding the frame alone be enough? Can the simple contact of the lid resting on the frame provide an adequate bond?

I'm not at all worried about metal covers on light pole bases; as far as I'm concerned, the mounting screws ensure a bond to the pole.

What I'm imagining is a cover at grade, where the wires were either damaged by getting pinched between the frame and the cover, of by simple friction of the wire rubbing against the cover every time the cover shifts with traffic.

I think there have been enough accidents for this to be a risk we need to address. The issue is also complicated by the inability to replace older boxes, and the absence of any need for these handholes to be listed. That is, there may not be an easy means of bonding provided, and we'll have to design it ourselves.

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#189607 - 10/19/09 01:22 PM Re: Bonding of a hanghole enclosure lid [Re: renosteinke]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
I suppose another relevant question would be whether these were service conductors or behind an appropriate overcurrent device that would operate in a fault. If they are service conductors you would need to bond with a 250.66 conductor to accomplish much. Simply laying in the frame would not provide adequate bonding but I bet an energized cover would dance if the frame was bonded, until it welded itself shut wink
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#189618 - 10/19/09 09:01 PM Re: Bonding of a hanghole enclosure lid [Re: gfretwell]
Niko Offline
Member

Registered: 08/17/06
Posts: 358
Loc: Campbell, CA
This was question from one of my students who is working for a solar company. My recommendation to him was to bond the lids. this is an accident waiting to happen, maybe not yet but over time it may happen, especially that is is in a school yard.

The handhole enclosures are being used as loop through pull boxes only, and the conduits are PVC and the feeder do contain the appropriate size EGC.
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