NEC 300.4(E) requires wiring that is not GRC of IRC to be installed 1 ? inch away from ?nearest surface? of roof decking. If I have a pan deck roof with a channel that is 4? wide and 3? deep I read the code as being able to install wiring in the ?Chase? of the pan deck as long as no part of the wiring is within 1 ?? of any surface of the pan deck. The picture in the Analysis of Changes to the 2008 NEC states and shows in pictures that the wiring must be installed 1 ?? from the lowest part of the pan deck. What is the proper interpretation?
Nec 300.4(e)
- Thread starter wyboy
- Start date
- Status
- Location
- New Jersey
- Occupation
- Journeyman Electrician
What is the surface above that big 4" X 3" pan? For roof decking the wiring, other than IMC or RMC, would need to be at least 1.5" away from the bottom of the pan even if it were 6" deep. I've said it before and I'll say it again, I hate this rule. 
- Location
- Massachusetts
You have to be 1.5" down from the lowest part of the deck, the intent of the rule is to directly prohibit us from running in the 'chase'.
As Rob said, I hate this rule.
As Rob said, I hate this rule.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
:grin:
Running EMT on the underside of these types of structures has been SOP for decades. Yes, there is a possibility of a screw penetrating a piece of EMT but given the additional cost factor involved to use strut or RMC/IMC, it would be cheaper to simply repair any conduit that were damaged then to not allow them to be installed that way in the first place.
- Location
- Illinois
- Occupation
- retired electrician
The rule does not say you have to be 1.5" away from the bottom of the pan. It says from the nearest edge. In the case posed by the original post, I don't see a violation if a conduit is run the "pan" space as long as the conduit is at least 1.5" from the nearest edge. Granted that would not provide the protection that was envisioned when the rule was written, but it would meet the wording of the rule.What is the surface above that big 4" X 3" pan? For roof decking the wiring, other than IMC or RMC, would need to be at least 1.5" away from the bottom of the pan even if it were 6" deep. I've said it before and I'll say it again, I hate this rule.
Proposal 3-34 for the 2011 code was accepted and would require that the top of the raceway be at least 1.5" below the lowest surface metal roof deck.
A few months ago I responded to a emergency service call for a supermarket refrigeration was down. It turned out roofers screwed thru a 3/4 emt ran in the pan decking filled with 9 circuits feeding all the fans in the freezers.
They had to empty all the freezers into frozen truck trailers while we repaired the problem. It took 3 electricians 6 hours of ot to fix it.
They had to empty all the freezers into frozen truck trailers while we repaired the problem. It took 3 electricians 6 hours of ot to fix it.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
And what was the total cost of the repair? You would still save a load of money, thousands of dollars by using EMT for an entire building using the "old" method even if you has to make a repair at some point.
Hmmm, wire this entire 100,000 square foot warehouse with EMT instead of using RMC/IMC. Sounds like a huge savings in material and labor. Those saving would easily offset replacing a few pieces of pipe and wire.
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