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Cutting holes in boxes for multiple conduits #199771
03/07/11 11:57 PM
03/07/11 11:57 PM
W
wewire2  Offline OP
Member
Joined: Nov 2002
Posts: 244
California
I want to mount a 3r pull box over several odd angled, closely bundled metal conduits protruding from a concrete exterior wall as this would be the most esthetically pleasing method of hiding the mess. 300.10 and 250.97 are applicable and mechanical,metallic and electrical connections are required. I'm thinking.....
Mechanical = concrete and screws
Metallic and electrical = ground bushing(listed fitting)
I'm wondering if the UL listing on the box be voided. Caulking would be used around the top and sides of the box. What are your thoughts on this?

2017 / 2014 NEC & Related Books and Study Guides
Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199772
03/08/11 10:04 AM
03/08/11 10:04 AM
G
ghost307  Offline
Member
Joined: May 2005
Posts: 943
Chicago Illinois USA
It sounds like the UL Listing on the box would be history after you got done with it.
I got into an argument with an EC about mounting a 3R box to a wall and drilling holes in the back to screw it (with rubber washers) to the wall instead of using the exterior tabs.
I asked UL and they said that drilling those holes voided their listing; regardless of how they were filled later on.

It sounds like your real problem is the pre-existing crummy conduit job that you have, not just sticking a new box on it to make it look nicer.


Ghost307
Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199773
03/08/11 10:20 AM
03/08/11 10:20 AM
HotLine1  Offline

Member
Joined: Apr 2002
Posts: 6,967
Brick, NJ USA
OK, I have a question...

1: Using the mounting tabs from the mfg
2: Using 'Myers Hubs' or the 'approved sealing locknuts' (2 on each conduit.
3: Caulk/seal the conduit openings in the wall only.

What would be non-compliant about that?



John
Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199775
03/08/11 11:19 AM
03/08/11 11:19 AM
G
George Little  Offline
Member
Joined: Jan 2004
Posts: 1,489
Michigan USA
I was born and raised on a farm in wisconsin and my mother had an expression that works here- "You can't make a silk purse out of a sow's ear" and when the original install was non code compliant, and it appears that was the case, it's sometimes not cost effective to correct it. I assume the inspector approved it right ha ha.

Sounds like the rules for conduit spacing are violated and the conduits are set in concrete so your stuck. I suspect the conductor bending violates the code also even it it's only a splice box. NEC 314.28.

I would suggest a conversation with the inspector and hopefully he can work with you on a solution that involves minimal cost and not break the rules and possibly only bend them a little to fit the situation.


George Little
Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199791
03/08/11 11:07 PM
03/08/11 11:07 PM
W
wewire2  Offline OP
Member
Joined: Nov 2002
Posts: 244
California
The conduits where installed in the 60's and
probably weren't even inspected. Ghost,I don't doubt you one bit about the UL response but since many pull boxes come without knockouts which means you have to make your own holes, I can't see how they can say it ruins the UL listing.Interesting!
John, great questions! Aside from the UL issue I haven't found the wording yet that absolutely prevents mounting the box that way. George, good point bringing up 314.28. The box would be sized for proper bending radius and would be used for through pulls. I think you're right. A chat with the inspector is in order. Thanks for the replies.

Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199796
03/09/11 09:53 AM
03/09/11 09:53 AM
G
ghost307  Offline
Member
Joined: May 2005
Posts: 943
Chicago Illinois USA
UL tests the blank boxes like this. They cut holes in them per the manufacturer's instructions and then installs/seals conduits per the instructions. Then they do their battery of tests for the Listing that's being sought.
If you don't cut holes and seal the conduits the same way, then you will have an installation that differs from the way that it was tested. UL won't stand behind a Listing mark on something installed differently than was tested.

I agree with George; see if the AHJ has any ideas on how to address this without having to redo the whole thing.


Ghost307
Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199802
03/09/11 10:36 AM
03/09/11 10:36 AM
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
IIRC ... and it's been several decades since I looked at THIS particular UL standard .... well, I don't recall there beiny ANY evaluation of your making holes. Let me sum up what I recall:

-Boxes had to either be of a certain thickness steel, or be evaluated for equivalent strength;

=They had to pass a modest corrosion test;

-These days, steel requires galvanizing as well as paint;

-Knock-outs, IF provided, were required to leave a hole that was free of sharp edges;

-There had to be a provision for grounding; and,

-Capacity had to be marked.

There were also tests for various environments IF the enclosure was asserted to meet those conditions. "NEMA-1" as simply required to not allow a 1/4" rod to contact live parts.

Now, that's for a simple box. If the box was (for example) for a control cabinet, then another standard entered the evaluation.

I think we place far too much on the shoulders of UL. Device straps line up with box mounting holes not because of any UL requirement, but because the manufacturers choose to design to their own (NEMA) specs. There is NO check on this apart from the manufacturer's desires.

UL is staffed by legions of second-rate engineers who all pretend that they're lawyers. They will never tell you that something is 'good' or 'bad.' The answer to EVERY query is "we can't know without a full evaluation."

Boxes are intended to have holes n them. All the UL tag does is tell you the box is a minimally decent raw material. YOU are the manufacturer, and it's up to YOU to do it right.

Likewise, the "AHJ" is the customer and the inspector - not UL, NEMA, NECA, or anyone else.

Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199803
03/09/11 10:55 AM
03/09/11 10:55 AM
H
harold endean  Offline
Member
Joined: Feb 2002
Posts: 2,233
Boonton, NJ
Maybe the AHJ can give a variation to the code or give it a 90-4 to allow it. You would be trying to do the best that you can under the circumstance. It might be worth a try.

Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199814
03/09/11 01:38 PM
03/09/11 01:38 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,225
Estero,Fl,usa
I don't see much of a problem in punching holes in the bottom of a 3R can. People usually drill weep holes in them anyway. wink

Sealing a hole in the top without using a hub in a specially punched hole can be a problem. The holes for them are usually flared with a raised edge to deflect water sitting on top.


Greg Fretwell
Re: Cutting holes in boxes for multiple conduits [Re: wewire2] #199832
03/10/11 12:17 AM
03/10/11 12:17 AM
W
wewire2  Offline OP
Member
Joined: Nov 2002
Posts: 244
California
Those gasketed K.O. seals work but usually when there's a
oops!in the top it's time for a new box. Don't want the
customer to get agitated.

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