General
We published a photograph in the "Code
Violations" section of the March/April 1995 IAEI News which
shows 21 service disconnecting means that are grouped in the
same location on the end of an apartment building. Four
service laterals supply the building from a common
transformer. The caption with the photograph indicates that
the installation is in violation of Section 230-71(a) of the
National Electrical Code® as there are more than six
disconnects grouped at the same location.
After getting a few phone calls asking for
clarification of the Code requirements as well as three
letters indicating disagreement with our conclusion, we
published a Closer Look article on services for
multiple-occupancy buildings in our July/August 1995 IAEI
News. The article was based on the rules in the 1993
NEC®.
We decided to take another look at these
requirements since several changes have taken place in Code
rules since that time. Some key definitions of terms used in
Article 230 have changed as well. Where used in this article
from this point on, terms that are defined in Article 100 are
in italics. That is just to help remind us that these terms
have precise meanings as used in the NEC®. As is true with
many discussions of subjects related to any code, it is
important to have a good understanding of definitions that
apply to the installation under consideration. These terms
have a specific meaning where used in the Code.
We will take a brief tour through some of
the basic requirements in the Code that apply to the
installation as well as review the applicable definitions.
This discussion is based on the 1999 National Electrical
Code®.
General Requirements
Section 230-2 has had a change of format as well as been
rewritten to change the previous exceptions into positive
language. There is now a general rule that requires, "A
building or other structure served shall be supplied by only
one service unless permitted in (a) through (d)."
These subsections contain six of the former seven exceptions
to the general rule. Language identical or similar to this has
been in many editions of the Code. For the purpose of our
discussion, we will assume that the multifamily dwelling under
consideration does not have a fire wall that would qualify as
a building separation as mentioned in Article 100. In
addition, we will not cover Section 230-2(a) Special
Conditions (applies to installations of services for fire
pumps, emergency systems, etc.) or Section 230-2(d) Different
Characteristics, as multifamily dwellings are generally
supplied at one voltage level and system type.
Some Definitions
As an aid to the reader, we have underlined new words
added to the definitions since the 1996 NEC® and struck
through words that are deleted. The definition of "service"
has been revised in the 1999 NEC® and is now defined in
Article 100 as, "The conductors and equipment for
delivering electric energy from the serving utility electricity supply system to the wiring
system of the premises served." These changes clarify
that on-site power production such as solar photovoltaic
systems, generators and power production facilities such as
cogeneration systems are usually separately derived systems and not services. The term "service"
is a broad term that includes the service drop, service
lateral, service-entrance conductors (both overhead
and underground system) and service equipment which
includes the service disconnecting means. Of course, the
definition of "equipment" is also a very
broad general term that includes "material, fittings,
devices, appliances, fixtures, apparatus, and the like used as
a part of, or in connection with, an electrical
installation."
The term "service equipment"
has also been revised in the 1999 NEC® and is now defined in
Article 100 as, "The necessary equipment, usually
consisting of a circuit breaker(s) or switch(es) and fuse(s), and their accessories, connected to the
load end of service located near the point
of entrance of supply conductors to a building
or other structure, or an otherwise designated defined area, and intended to constitute the main control and means
of cutoff of the supply." As can be seen, the
term "service equipment" includes the
equipment, such as switches and fuses as well as circuit
breakers, that are used as the "service disconnecting
means."
The term "service disconnecting
means" is not defined in the NEC®, although the term is
used in several articles including the definition of "service
conductors" in Article 100. Section 230-70 contains
several requirements for the service disconnecting means and
also describes its purpose. The service disconnecting means is
or are provided to "disconnect all conductors in a building or other structure from the service-entrance conductors."
It must be located "at a readily accessible location either outside of a building or structure or inside
nearest the point of entrance of the service conductors."
Each service disconnecting means must be permanently marked to
identify it as a service disconnecting means and must be
suitable for the prevailing conditions, such as being suitable
for a wet location.
The term "building" is
defined in Article 100 as, "A structure that stands alone
or that is cut off from adjoining structures by fire walls
with all openings therein protected by approved fire
doors." The term "structure" is not defined in
the Code although Section 230-21 mentions "such as a
pole" when describing an "other structure."
Since the term is not defined in the Code, we can use a common
dictionary definition such as "Something made up of a
number of parts held or put together in a specific way."
So, we can apply the rules for installation of service
equipment to any building or structure the service
equipment is mounted in or on.
The term "service conductors"
has also been revised in the 1999 NEC® and now is defined in
Article 100 as "The supply conductors
that extend from the service point street
main or from transformers to the wiring system service equipment of the premises
supplied." The term "service conductors"
is a broad term that includes: "service drop,"
"service-entrance conductors, overhead system,"
"service-entrance conductors, underground system"
and "service lateral." This change
coordinates with Section 90-2(b)(5) which indicates that
installations under the exclusive control of electric
utilities for distribution of electric energy are not covered
by the Code. However, these same conductors installed by the
owner, contractor or electrician are covered by the Code.
As can be seen, the conductors supplied by
an electric utility on the line side of the "service
point" are now not considered by the Code to be "service
conductors." The term "service point"
is defined in Article 100 as, "The point of connection
between the facilities of the serving utility and the premises
wiring." This means that where the service point is at the building or structure such as the connection at the
weatherhead for overhead services or at the meter
socket for underground services, the service drop and service lateral are not covered by the Code.
The following definitions also apply to our
discussion and should be understood:
"Service Drop: The overhead service conductors from the last pole or other aerial support to and
including the splices, if any, connecting to the service-entrance
conductors at the building or other
structure."
"Service-Entrance Conductors,
Overhead System: The service conductors between the
terminals of the service equipment and a point usually
outside the building, clear of building walls, where joined by
tap or splice to the service drop."
"Service-Entrance Conductors,
Underground System: The service conductors between
the terminals of the service equipment and the point of
connection to the service lateral.
(FPN): Where service equipment is
located outside the building walls, there may be no service-entrance
conductors, or they may be entirely outside the
building."
"Service Lateral: The
underground service conductors between the street main,
including any risers at a pole or other structure or from
transformers, and the first point of connection to the service-entrance
conductors in a terminal box or meter or other enclosure with
adequate space, inside or outside the building wall.
Where there is no terminal box, meter, or other enclosure with
adequate space, the point of connection shall be
considered to be the point of entrance of the service
conductors into the building."
Section 230-2
With these definitions in mind, let’s look at the
requirements in Section 230-2 for installing a service for a multiple-occupancy building. The general rule in this
section is that "A building or other structure shall be
supplied by only one service unless permitted in (a)
through (d)." Keep in mind that the term "service"
includes, "The conductors and equipment for delivering
electric energy from the serving utility to the wiring system
of the premises served."
Figure
1 shows an overhead service to a building and an
underground service to another.
The general requirement is that only one service
drop or service lateral is permitted to be run to a
building or other structure where the service equipment is located. Why? Because the term "service"
includes both the "service drop" and "service
lateral" and Section 230-2 generally permits only one service to a building or structure. The service drop will connect to service-entrance conductors, usually
"outside the building, clear of building walls."
(See the definition in Article 100.) As can be seen in the
definition of "service lateral," where
the service lateral stays outside the building such as
supplying weatherproof service equipment, there are no service-entrance
conductors.
Structure with a Fire
Wall
A structure with a fire wall that qualifies as a building
separation is considered to be more than one building as
determined by the number of fire-wall separations. For
example, a structure with one fire wall will be two buildings.
The fire resistance rating of a fire wall required to qualify
as a building separation is not given in the NEC®. It is
necessary to obtain the details on fire-wall construction to
create a building separation from the applicable building
code. Usually, a fire wall having not less that a two-hour
rating is required to create a building separation. Each of
these buildings is then generally permitted to have not more
than one service to it. Have you seen a duplex
(two-family dwelling) with two service drops or service
laterals to it? This is a violation of Section 230-2
unless the structure has a qualifying fire wall.
A permanent plaque or directory is required
where more than one service is permitted for any
reason, be it fire-wall separation or one of the conditions of
Section 230-2(a) through (d). This requirement applies where a
building or structure is supplied by any combination of more
than one service, feeder or branch circuit. The
plaque or directory must be located at each service disconnect
location and must indicate all other services, feeders or branch circuits supplying that building or
structure and give the area served by each of them. See
Section 230-2(e).
Section 230-2(b)
Special Occupancies
(This previously was Section 230-2 Exception No. 3,
Multiple-Occupancy Buildings.) This subsection permits
additional services, by special permission, for
(1) Multiple-occupancy buildings where there is no space for service
equipment accessible to all occupants, and for (2) A
single building or other structure sufficiently large
to make two or more services necessary.
The term "multiple-occupancy
building" is not defined in the NEC® but "multifamily
dwelling" is. Traditionally, the term multifamily
dwelling has been interpreted as a multiple-occupancy
building in applying the rules of the NEC®. Building codes
tend to use the term "occupancy" as referring to a
class of users of a building such as "business use,"
"educational use" or "residential use."
So, a multiple-occupancy building in building code terms would
have more than one type of occupancy in the same building and
might be referred to as a "mixed use or occupancy"
building. The NEC® tends to use the phrase
"multiple-occupancy building" as one having more
than one occupant rather than more than one class of occupant.
Figure
2. Section 230-2(b)(1).
Section 230-2(b)(1)
Note that Section 230-2(b)(1) permits an additional service(s) where there is "no available space for service
equipment," that is "accessible to all the
occupants." It seems there will always be space available
for a single main disconnecting means, or up to six
disconnecting means grouped at one location that is be
accessible to all the occupants. This service equipment does not have to be inside such as in an electrical equipment
room but can be located outside on or adjacent to the
building. The location rule is in Section 230-70(a) and reads,
"The service disconnecting means shall be installed at readily
accessible location either outside of a building or
structure or inside nearest the point of entrance of the service
conductors." Economical design criteria may dictate
not installing a single main service disconnecting means but
that consideration is not given in this Code rule. In
addition, there may not be space at one location for all the
metering equipment and individual meter/mains needed for a
large complex. However, this section does not address
multi-metering or feeder disconnecting means for all the
individual occupancies. The installation in the photograph at
the beginning of this article fails the test for this
subsection as there certainly appears to be space at the
location chosen for the multiple services for a single service to be installed with meter/feeder supply to the
individual dwelling units.
There is no requirement in this rule that
the space available for the service equipment that is
to be accessible to all the occupants must be inside the
building. It is quite common to locate service equipment outside multiple-occupancy buildings as indicated in the
photograph that accompanies this article. If there is space
for the service equipment in a common area, including
outside, that is adequate for the service equipment for the
building, Section 230-2(b)(1) cannot be used. If space is
available for the service equipment to serve all
the occupancies, then, according to the main rule, only one service is permitted for the building with a maximum of six
disconnects. (We will look at some other provisions a little
later in this article.)
Where the main disconnecting means is or
are located before the metering equipment, it is common for
the serving utility to require that the service disconnecting
means enclosure be locked to reduce the likelihood of
tampering and theft of electrical energy. The authorization
for more than one service in Section 230-2(b) must be
by "special permission," which is defined in
Article 100 as "The written consent of the authority
having jurisdiction."
It is not necessary for there to be a fire
wall separation to grant the "special permission"
provided for in this subsection. As provided in Section
230-2(b), "special permission" is to be based
on space-for-equipment considerations. Six service
disconnecting means are permitted to be installed for each
additional service that is allowed by the authority
having jurisdiction under Section 230-2(b)(1). The Code does
not clearly require that the additional services installed as permitted by this subsection be installed at a
location separate from the other service(s) to the building.
For example, a building is supplied by a 120/240 volt,
single-phase service with six service disconnecting
means grouped at one location. A second service, this
one a 208Y/120 volt, three-phase service, can be
installed immediately adjacent to the single-phase service with an additional six service disconnecting means. See
Section 230-71(a).
Section 230-2(b)(2)
(This previously was Section 230-2 Exception No. 5,
Buildings of Large Area.) Again, by special permission,
one or more additional services are permitted for
"A single building or other structure sufficiently
large to make two or more services necessary."
No guidance on how to determine what
qualifies as a "building of large area" is
provided in the NEC®. Large industrial plants where lengthy feeder runs would cause excessive voltage drop which would require
increasing the conductor size unreasonably is an example of
where this exception may be applied. Other examples are large
shopping centers or high-rise office buildings. The authority having jurisdiction is pretty much left on his own when
attempting to determine when to allow this subsection to be
applied.
Obviously, this subsection does not apply
to the installation under review as there are no long feeder runs involved.
Section 230-2(c).
Capacity Requirements
(This subsection is the former Exception No. 4 to Section
230-2.) This subsection permits additional services to
a building or other structure for only the following
reasons, all of which are related to the capacity or size of
the service:
"(1). Where the capacity requirements
are in excess of 2000 amperes at a supply voltage of 600 volts
or less; or
(2). Where the load requirements of a
single-phase installation are greater than the serving agency
normally supplies through one service; or
(3). By special permission."
Figure
3. Section 230-2(c).
Condition "(1)" does not apply to
this installation as there is no service in excess of
2000 amperes. The total ampacity of the four service
laterals do not come close to 2000 amperes. In fact, the
size of the four service laterals could no doubt be
smaller if they were combined to serve all the loads. This is
due to the increased demand factors permitted by Article 220
for load calculations as the number of units served increases.
One disadvantage of installing the service
lateral conductors in parallel (connected together at both
ends to form a larger conductor) is the fault current
available at the service equipment will be greater than
where individual sets of conductors are run to separate service
equipment enclosures.
Condition "(2)" does not apply as
the four service laterals shown in the photograph are
from the same transformer and thus obviously do not exceed the
capacity of the serving utility’s transformer.
Condition "(3)" provides for special
permission from the authority having jurisdiction. To
apply in this situation, the special permission must
relate to the capacity of the system. Condition
"(3)" does not seem to apply to the installation
under review as there is no need for an additional service based on capacity considerations. The single transformer
installed by the utility has adequate capacity for the load.
Sections 230-2 and
230-40 Exception No. 2
Former Exception No. 7 to Section 230-2 has been
incorporated into the opening paragraph of Section 230-2 as a
new second sentence. The sentence reads, "For the purpose
of Section 230-40, Exception No. 2 only, underground sets of
conductors, size 1/0 and larger, running to the same location
and connected together at their supply end but not connected
together at their load end shall be considered to be supplying
one service." This sentence really does not allow
an additional service in the strictest sense but allows
several sets of service lateral conductors to be
considered as supplying one service. (In reality, the service
lateral does not supply the service but is a part
of the service as defined in Article 100.)
Figure
4. Sections 230-2 and 230-40 Ex. No. 2.
As indicated, the second sentence of
Section 230-2 is limited in application to Section 230-40
Exception No. 2. It reads, "Where two to six service
disconnecting means in separate enclosures are grouped at one
location and supply separate loads from one service drop or lateral, one set of service-entrance conductors shall be permitted to supply each or several such service
equipment enclosures."
As illustrated in Figure
4, a maximum of six service laterals, sized 1/0 or
larger, that are connected together at their line end, but not
at their load end, are considered to be supplying one service.
The service laterals must be run to a common location
at the building or structure served and are permitted to
supply one, two or up to a total of six service disconnecting
means. However, no more than six disconnecting means are
permitted to be grouped at the location being served by these service
laterals. See Section 230-71(a).
Section 230-40
Exception No. 1
Section 230-40 generally permits a service drop or service
lateral to supply not more than one set of service-entrance
conductors. When taken with the requirements of Section
230-2 and the definition of "service" in
Article 100, this means that a building or other structure can
generally be supplied by only one service drop that
connects to one set of service-entrance conductors or
it can be supplied by one service lateral that connects
to one set of service-entrance conductors.
Exception No. 1 to Section 230-40 provides
that, "Buildings with one or more than one occupancy
shall be permitted to have one set of service-entrance
conductors for each class of service run to each
occupancy or group of occupancies."
Figure
5. Section 230-40 Exception No. 1
Figure
5 illustrates an underground supply to a
multiple-occupancy building. A similar procedure can be
followed for an overhead supply. While only six units are
shown due to space limitations, any number of units may be
served in a similar manner.
The service lateral supplies a
metering cabinet that does not contain service disconnecting
means or overcurrent protection but has only meter sockets. A
set of service-entrance conductors is run to each
occupancy or to a group of occupancies. Of course, these service-entrance
conductors do not have overload protection until they
terminate in the service equipment. Where this scheme
is selected, it is customary to run service-entrance
conductors to the individual units rather than to a group
of units. Up to six disconnecting means are permitted in or on
each of the units, and of course, they must be grouped at the
individual locations to comply with Section 230-71 (a).
As indicated in the Figure
6, service lateral conductors are run from the
utility transformer to a wireway mounted below the meter
sockets. Service-entrance conductors are spliced to the service lateral conductors within the wireway and run
through the meter sockets to each unit. Service disconnecting
means and overload protection is provided in or on each
unit.
The location of the service disconnecting
means must comply with Section 230-70 (a) which requires,
"The service disconnecting means shall be installed at a readily
accessible location, either outside of a building or structure or inside nearest the point of entrance of the service
conductors." Some inspection jurisdictions interpret,
"nearest the point of entrance of the service
conductors" to require the service equipment to be located in the stud space in the outside wall or
back-to-back with the meter socket or point of entrance.
Others interpret this rule to permit up to four feet of service-entrance
conductors inside the building, while still others permit
as much as 25 feet of service-entrance conductors to be
installed inside the building. In some cases where these
longer lengths of service-entrance conductors are
permitted inside the building by local rule, a limited number
of wiring methods are permitted. Be certain to verify the
local rule or interpretation before beginning an installation.
Section 230-71(a)
This section provides that, "The service
disconnecting means for each service permitted by
Section 230-2, or for each set of service-entrance
conductors permitted by Section 230-40, Exception Nos. 1
or 3, shall consist of not more than six switches or six
circuit breakers mounted in a single enclosure, in a group of
separate enclosures, or in or on a switchboard. There shall be
no more than six disconnects per service grouped in any
one location." Since the term "location" is not
defined in the Code, it will be applied based on its common
dictionary meaning. As this word applies to the installation
in the first photograph, most people probably would apply the
meaning of "location" to be that all the service
disconnects shown are at the same "location" since
they are immediately adjacent to each other at the same end of
the building. Most people would likely consider the services to be in different "locations" if a service were
installed some significant distance apart such as at opposite
ends of the building.
As we previously mentioned, more than six
service disconnects are permitted at the same location only
where more than one service is permitted to a building.
For the installation under consideration, it does not appear
that any of the rules in Section 230-2(a) through (d) apply so
only one service with a maximum of six disconnecting
means is permitted.
Section 230-72
This section generally requires the service disconnecting
means permitted by Section 230-71 to be grouped.
In a multiple-occupancy building, each
occupant is required to have access to their service
disconnecting means. The exception to Section 230-72(c) allows
the service disconnecting means that supplies more than one
occupancy to be accessible to authorized building management
personnel only where the electric service and electrical
maintenance for the building are under continuous
building management supervision. This exception does not apply
to the multiple-occupancy installation under consideration as
all the service disconnecting means are on the outside at a
common location and are accessible to each of the occupants.
Conclusion
As can be seen, there are many different ways to
install the service for a multiple-occupancy building
and be in compliance with the National Electrical Code.
To do so requires a thorough reading and understanding of the
definitions and Code requirements that apply. As you have
probably observed, the installation shown in the photograph at
the beginning of this article did not comply with the 1993 or
1996 NEC and would not comply with the revised rules of
the 1999 NEC Article 230.
Serving utilities may have local
requirements regarding serving multiple-occupancy buildings
that must be complied with. These utilities often have
booklets with diagrams that illustrate their distribution
requirements.
Finally, the authority having jurisdiction
may have local amendments to the Code that must also be
complied with as well. These amendments will be in the form of
legally adopted ordinances, regulations or statutes and are
not simply an unwritten interpretation. These local
amendments, if any, are also available in writing from the
inspection agency.
J. Philip Simmons has written and
illustrated several authoritative books on electrical
systems. He is acting chair of NEC CMP-5, chairman of
IAEI Neon Installation Manual, and a member of the
Inspector Certification Exam Committee. He is a former
employee of NFPA Standards Council and NEC Technical
Correlating Committee, past chair of NFPA Electrical
Section, former member of NEC CMP-1 and 17, and past
chairman of CMP-19. |
