box within a box

[katyajani]

has anybody hear about dade county requirement of a box within a box requirement when it come to a junction box to a lighting pole?

according to dade county and in reference to article 300.12,300.5,314.15
when installing underground raceway and they emerge to a pull box. these conduits have to be continuous therefore a pull box need to be installed and another hand hole box also needs to be installed. I understand what they want but I do not believe that was the intention of the code, when it comes to underground raceways

please comment.

 

[tom baker]

Re: box within a box

This sounds like an open bottom handhole for roadway lighting. Open bottome handholes (OBH) are commonly used for this application, however this method is not exactly recognized by the NEC, and there is proposal to add OBH to the scope of art 314. An OBH can be a safe wiring method, if done properly. Many state DOT's have specs to allow the method, and Washington State has a state code rule that allows it. If thats what they want then you may not be able to do it otherwise.
Here is the Washington State method-it admends the NEC:
"WAC 296-46B-314 Wiring methods and materials--Outlet, device, pull and junction boxes.
001 Boxes and fittings.
(1) Single conductors, cables, taps, or splices installed in an open bottom junction box or handhole must be suitable for direct
burial. However, an open bottom box manufactured specifically for electrical use will be permitted to be used as an
electrical junction box to enclose single conductors, cables, taps, or splices rated for wet locations, only under the
following conditions:
(a) In vehicular traffic areas the box must be rated for not less than H-20 loading and be provided with a bolted,
hinged, or slide-on lid embossed with the identification "ELECTRIC" or "ELECTRICAL."
(b) In incidental vehicular traffic areas (e.g., parks, sports fields, sidewalks, grass lawns, etc.) the box must be rated
for not less than H-10 loading and be provided with a bolted, hinged, or slide-on lid embossed with the
identification "ELECTRIC" or "ELECTRICAL."
(c) In nonvehicular traffic areas (e.g., flower beds, patio decks, etc.) the box must be designed for the purpose and be
provided with a lid embossed with the identification "ELECTRIC" or "ELECTRICAL."
(d) All conductors must be installed in approved electrical raceways that enter vertically from the open bottom of the
enclosure. These raceways must be fitted with a bushing, terminal fitting, or seal incorporating the physical
protection characteristics of a bushing, and project not less than 5 cm (2") above the bottom surface material.
The bottom surface material must be pea gravel or sand a minimum of 5 cm (2") thick or more if required by the
box manufacturer."
Also if its a metal lid then it needs to be bonded. Quartzite is the only mfg I know that makes a UL listed OBH.

[ January 05, 2004, 02:57 PM: Message edited by: tom baker ]