What does "under 2" of concrete mean"

[Sifu]

NEC 2014
230.6 Conductors Considered Outside the Building.
Conductors shall be considered outside of a building or
other structure under any of the following conditions:
(1) Where installed under not less than 50 mm (2 in.) of
concrete beneath a building or other structure
(2) Where installed within a building or other structure in a
raceway that is encased in concrete or brick not less
than 50 mm (2 in.) thick

The condition we are looking at is a cluster of service cables in PVC conduit, running in an 18" crawlspace, on the dirt. The floor above is a metal deck and concrete slab. The question is whether this meets condition #1 since it is under 2" of concrete and would be permitted as beneath a building, or do they need to be encased as in #2. IF running these conduit, under a concrete floor, under a building (in the crawl) meets #1, then t300.5 would allow 0" of burial and would appear to be allowed. This is an existing office building undergoing a remodel. The crawlspace is only accessible by hatch and crawling. Some here believe the conduit needs to be encased, some believe it is OK as is. Since the code appears to make a distinction between under and encased I am not sure. Opinions?

 

[north star]

@ ~ @

Sifu,

IMO, in your application, the conductors are considered
to be outside the building, because they are located
underneath the metal decking and concrete slab....."IF"
the concrete slab is a minimum of 2" or greater......The
FPN & visual Exhibits in the NEC Handbook clarify this more.

IMO, ...your conductors and raceways are acceptable
"as is" "IF" they are installed correctly.

+ ! +

 

[CityKin]

I don't think this meets the intention of the code. Unfused service conductors in a crawlspace would be a hazard unless encased in concrete. Imagine in 20 years someone getting down in the crawlspace to install a plumbing line and accidentally damaging this while in such a confined space.

 

[fatboy]

I agree with CityKin, I believe the intent is to be directly encased with 2" minimum concrete cover.

JMHO

 

[Sifu]

I can see it both ways. The distinction between encased and under makes me question this. The intent is to protect the feeders, and by running them as they are, they are protected from everything except somebody in the crawlspace. . I just went out to see it with the inspector, he is of the same opinion as citykin and fatboy. The feeders are a straight shot from the equipment out of the building and easy enough to encase so that is the way I went. I still see some grey area here, but it is easy enough to err on the side of caution in this case.

 

[mark handler]

NEC 2014, Handbook, 230.6 (4) Where installed in conduit and under not less than 450 mm (18 in.) of earth beneath a building or other structure.

Code is clear- 2" of Concrete or 18" of dirt

 

[steveray]

concrete over, dirt around IMO....Not exactly "encased" but that is the intent. Otherwise you could run them anywhere in a concrete deck building...

 

[Sifu]

Otherwise you could run them anywhere in a concrete deck building...

That is ultimately the argument I was thinking of. Looks like under and encased is a distinction without a difference in this case.

 

[mtlogcabin]

I think 230.50 (2017 NEC) is more applicable to what you are describing and would be code compliant

 

[Sifu]

"Under a building" is still the sticky wicket. I don't know how a cable can be "under a building" with 0" of cover as indicated in 300.5. But I also see how a cable running along the surface of the ground is subject to damage, and like steveray posted, where would you draw the line? My chief electrical inspector wants it encased, I'm not sure, and the contractor has agreed to do it. All of that equals a settled matter, at least in this case. Though I will keep looking for input.

 

[north star]

% = % = %

Table 300.5 [ in the NEC ] allows your application, with 0 [ zero ] inches
of cover, ...as long as the pvc raceway is installed correctly !

The correctly installed pvc raceway IS the protection !

% = % = %

 

[steveray]

% = % = %

Table 300.5 [ in the NEC ] allows your application, with 0 [ zero ] inches
of cover, ...as long as the pvc raceway is installed correctly !

The correctly installed pvc raceway IS the protection !

% = % = %

Not for "service conductors" I don't believe....Which is the OP situation...

 

[north star]

# ~ #

**steveray**,

I believe that you are correct sir !........My "most humble"
apologies to all !.........I stand corrected !

# ~ #

 

[Sifu]

Yes, these are un-fused secondary conductors.

 

[ADAguy]

When in doubt, it is not the conductors you should be concerned with protecting it is the human who may come into contact with them. Its a life safety issue, see OSHA.

 

[ICE]

Yes, these are un-fused secondary conductors.

A main disconnect is required nearest the entrance to the structure.

 

[Gregg Harris]

Encased would be the correct interpritation

 

[fatboy]

Glad to see you around again Gregg..............