DOLLARD is the safety coordinator for IBEW Local No. 98 in Philadelphia and works closely
with contractors to ensure job-site safety and compliance with all installation codes and
standards. He is a member of the NEC Correlating Committee, NEC CMP- 10, NEC CMP- 13, NFPA
70E, NFPA 90A/B and the UL Electrical Council. He can be reached at
Continued from page 30
requirement where the 2011 NEC is
Surface metal raceway
When calculating the conductor
fill in surface metal raceway, is
it permitted to determine the
allowable fill by using the conductor
sizes in square inches from Table 5
and the approximate square-inch
measurement of the individual
surface metal raceway?
No, Section 386.22 provides requirements for the number of permitted
conductors or cables in surface metal
raceway. The raceway design will determine the maximum number of conductors
permitted, not a calculation. See the manufacturer’s labeling and instructions.
Manufacturers of surface metal raceway provide conductor fill information
for all of their products. I suggest you
determine the number of conductors the
installation needs and the appropriate
size of surface metal raceway, to install
by visiting the manufacturers’ website
On a recent job, we had many discussions
about fireproofing openings in fire-rated
walls. We struggled, but the electrical
inspector was well-versed in applicable
building codes and was a big help.
Section 300.21 is quite confusing. The
first sentence tells us that we must
install so that the spread of fire is not
“substantially increased.” What does
that mean? Is a little fire OK? The rest
of the requirement basically tells us to
use approved fire-stopping materials.
The informational note does steer the
user to parties that can provide more
information, but this is confusing as well.
My research shows the 24-inch spacing
always applies. Also, every opening must
be fire proofed, not just those without
minimum spacing. Why is the NEC so
vague here? We should have the exact
requirements in 300.21.
No, a little fire is not OK! When we
penetrate a fire-rated assembly, it is
compromised. Yes, we will fireproof the
opening, but it is not equal in rating to
a similar assembly without penetration.
That is the reason the NEC states, “will
not be substantially increased.”
Section 300.21 contains general
requirements for the fireproofing of any
penetration in any fire-rated wall, floor
or ceiling that is made as part of an elec-
trical installation. The requirements for
fireproofing openings made in fire-rated
assemblies to install raceways, cable
assemblies and other electrical equip-
ment are outside of the NEC’s scope.
Other codes and standards will provide
prescriptive requirements for fireproof-
ing these openings. Section 300.21 is a
performance-based requirement. We
cannot get prescriptive because there are
far too many different scenarios encoun-
tered when fireproofing.
Also, the building codes that address
fireproofing are subject to change. The
requirements themselves may change,
and the authority having jurisdiction
determines which edition of applicable
codes and standards applies in your
area. I do believe the informational note
should be expanded or a new infor-
mational note added to reference
applicable sections in building codes
for NEC users. Be sure to submit
your ideas in the form of a public
input for the 2020 NEC.
Branch circuit or
When installing branch circuits at 15
and 20 amperes (A), the NEC has strict
rules on the rating of receptacles with
respect to the size of the branch circuit.
If we have a load such as a standard
dwelling-unit refrigerator, and we put it
on its own 20A branch circuit, why must
we install a 20A receptacle when the
cord is a 15A configuration? The same
holds true for a 15A branch circuit: why
can’t I just use a 20A receptacle? The 15A
breaker will never allow more than 15A.
The general NEC requirement for single receptacles on an individual branch
circuit in Section 210.21(B)( 1) requires
the receptacle to have an ampere rating
not less than the branch circuit rating.
This is based on the fact that this is
an individual branch circuit, which by
definition supplies only one piece of utilization equipment.
The intent of this rule is to size the
receptacle to allow for a single utilization equipment with the same rating
of the branch circuit to be supplied.
While your question discusses a single
dwelling-unit-type refrigerator with
a 15A cord cap, there are refrigerators
that are rated and supplied with a 20A
cord cap. Where a 15A branch circuit is
installed, the NEC prohibits the installation of a 20A receptacle. This is to
prevent utilization equipment rated at
20A from exceeding or overloading the
15A branch circuit.
No, a little fire
is not OK!