For those of us who have been using the NEC for a
number of years, when looking at the 1999 edition, we see a
whole new document. This will be a cycle of relearning what we
already know. Along with the changes is the relocation of a
lot of existing information. It would be impossible to explain
all of the rework and changes in Article 240 in just one short
article. It is my recommendation that you check the IAEI
News for a seminar in your area and attend it.
But let us browse through Article 240, examining the
highlights briefly:
Section 240-3(d) Small Conductors is a relocation from
the bottom of Table 310-16. There is not anything new here; it
was felt that the rule would be better served if this
information were located in the Overcurrent Protection Article
and that it would, possibly, be easier to find.
Section 240-3(e) Tap Conductors now have a definition of their own as used
in 240. In the past there were major abuse and misuse of the
rules for a tap conductor and there was not a clear statement
as to what a tap conductor is. Hopefully the definition will
clear up any questions as to what is a tap conductor.
Section 240-6(c) Restricted
Access Adjustable-Trip Circuit Breakers now defines what
"restricted" means and what has to be done to comply
with the rules of installation. There are three ways to
restrict access and at least one of the three must be met.
Section 240-21 Location in Circuit has undergone some
major rewrite that did not cause any code requirement changes
but it will make life a lot easier when applying the rules.
There is now a separation of taps to feeders from the
requirement for transformer secondaries.
Section 240-21(a) has been divided into two parts: (a)
Branch-Circuit Conductors specifies that for this tap one
must comply with Section 210-19. The new (b) Feeder Taps
lets one know that he is now in the rules for feeder taps. The
wording in the 10 ft. tap rule was changed from "the line
side of the tap conductor shall not exceed 1,000 percent of
the tap conductor’s ampacity" to "shall not exceed
10 times the ampacity of the tap conductor." This change
was made simply to make the understanding of the math easier.
If this still confuses some people you could always do the
math both ways. The greatest change was really the
rearrangement so that all of the 10 ft. rules are in one
location and all of the 25 ft. rules are in another location
and so on, you get the idea.
Under Section
240-21(b)(5) Outside Taps of Unlimited Length did not
see any significant changes here. Perhaps the most significant
event here is something that did not happen. There were a
number of proposals and comments for the rule to allow
termination in up to six disconnects instead of one. The main
argument here was that it is felt, by the proposers and
commenters, the number of disconnects should follow the same
rules as Service Equipment. The panel felt that they should
not be treated the same because of the differences between the
two and that there would be less overloading of the tap
conductors if limited to one disconnect rather than a maximum
of six. I think this one will be back.
There is an interesting clarification to Section
240-21(g) Conductors from Generator Terminals that now
spells out that the conductors are not protected from
short-circuit or ground-fault under the specifications of
445-4. The conductor sizing has changed and the wording in
445-5 provides for additional language for the sizing of these
conductors to afford them the protection needed.
These are some of the changes and relocation of information
in 240, but there are some major changes that I did not even
mention. I hope you found this to be of interest and may have
even picked up some new information that will be of help to
you in this new code cycle. I hope that I have an opportunity
to present some more of Article 240 in the future such as the
new Part H and the rewrite of Part I. Please do not feel as
though you have to wait for me, let one of the IAEI Seminars
introduce you to these exciting changes. Check your magazine
for dates and places, and check with your local chapter.
IAEI Eastern Section past president, John
E. Brezan is owner of Lehigh Valley Electrical Inspection
Service and Lehigh Valley Inspection Services. An electrical
inspector for the past 21 years, he is principal member of
Panel 10, representing the IAEI, member of NFPA, and PennBOC
Region II past member.
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