Electrical
Shortz
Date: 01/2010
Author: Jim Pauley
Document Number: 0100DB0708R01/10
Cedar Rapids, Iowa, USA
www.schneider-electric.us/go/codes
Keywords:
Panelboard,
Lighting and Appliance,
Power Panel,
42 Circuits,
42 Circuit Rule
Lighting and Appliance or Power Panelboards
The 2008 NEC removed the definitions of lighting and appliance branchcircuit panelboard and power panelboard. Many areas will continue to be
under the requirements of earlier editions of the NEC where the distinctions
between these must be understood.
What is a lighting and appliance branch-circuit panelboard? What is a power
panelboard? Is the panelboard required to be protected by a main circuit
breaker? What is the 42-circuit rule? Why do you manufacture a
panelboard? These are the common questions that arise when installing
panelboards in accordance with the NEC. The intent of this paper is to
assist your understanding in applying panelboards to meet the rules in the
NEC.
The Lighting and Appliance Branch
Circuit Panelboard
The first step in properly applying the panelboard rules in the 2005 and prior
editions of NEC 408 is to understand the branch circuit loads that will be fed
from the panel. The number of lighting and appliance branch circuits must
be identified:
“A lighting and appliance branch circuit is a branch circuit that has a
connection to the neutral of the panelboard and that has overcurrent
protection of 30 amperes or less in one or more conductors.”
The definition of a lighting and appliance branch circuit leads to the
identification of circuits with 30A or less circuit breakers. Panel 1 has ten
2-pole circuit breakers (20 overcurrent devices) installed and the 20 ampere
and 30 ampere branch circuits have a neutral conductor connected to the
panelboard. Keep in mind the number of overcurrent protection devices is
determined by the number of poles on the circuit breaker, hence a 2-pole
circuit breaker is considered two overcurrent devices.
The Square D® I-Line® panelboard removes the confusion between the
number of overcurrent devices and available spaces in the panelboard,
since there is no defined number of spaces in I-Line construction. The NEC
rules apply to the number of overcurrent devices not the number of spaces
available in the panelboard. Using the information provided, Panel 1 has 4
overcurrent devices protecting lighting and appliance branch circuits. The
second step is to calculate the percentage of overcurrent devices in the
panel protecting lighting and appliance branch circuits:
“A lighting and appliance branch-circuit panelboard is one having
more than 10 percent of its overcurrent devices protecting lighting
and appliance branch circuits.”
Panel 1 has 20 percent of its overcurrent devices protecting lighting and
appliance branch circuits, therefore Panel 1 is defined as a lighting and
appliance panelboard. NEC 408 requires each lighting and appliance
branch circuit panelboard to be individually protected on the supply side by
a circuit breaker or set of fuses not greater than the rating of the panelboard.
© 2008–2010 Schneider Electric All Rights Reserved
Lighting and Appliance or Power Panelboards
0100DB0708R01/10
01/2010
The panelboard can be protected by either an integral main overcurrent
device or an overcurrent device protecting the feeder to the panel.
The final restriction on the lighting and appliance branch-circuit panelboard
is that not more than 42 overcurrent devices (excluding the main) shall be
installed in any one enclosure.
Power Panelboard
If 10 percent or less of the overcurrent devices protecting lighting and
appliance branch circuits were found in the panelboard, it would be
defined as a power panelboard. If the panel is not a lighting and
appliance branch-circuit panelboard then it is a power panelboard by
default.
A power panelboard may also require line side overcurrent protection
not greater than the rating of the panelboard if both of the following
conditions exist:
A. The supply conductors to the panelboard include a neutral and
B. More than 10 percent of the overcurrent protection devices are rated 30
amperes or less.
A main is not required where the power panelboard is installed in a
service entrance application utilizing multiple disconnects (six
disconnect rule) in accordance with NEC 230-71.
So why is a 54 circuit (space) panelboard manufactured? The NEC
does not restrict the number of overcurrent devices in a power
panelboard enclosure. Circuit breaker accessories such as shunt trip,
auxiliary and alarm switches, may take a space in the panelboard, but
they are not an overcurrent device and as such are not counted as one
of the 42 overcurrent devices in a lighting and appliance panel.
Therefore a 54-circuit panelboard may still be applied as a lighting and
appliance panelboard in limited applications where the panel is factory
assembled. Listed panelboards shipped with more than 42 circuits
(spaces) and not with the overcurrent devices are marked “Lighting or
appliance branch circuits are not to be supplied directly through more
than 10 percent of the branch-circuit overcurrent protective devices.”
Summary
1. Identify the number of lighting and appliance branch circuits.
2. Calculate the percentage of overcurrent devices in the panel protecting
lighting and appliance branch circuits.
3. Determine if the Panelboard is a lighting and appliance branch-circuit
panelboard. If it is not a lighting and appliance branch circuit panelboard,
then it is a power panelboard.
Lighting and Appliance Branch-Circuit Panelboard
Power Panelboard
4. The panelboard must be protected by either an integral
main or by the feeder circuit overcurrent device.
4. Determine if the panelboard supply conductors include a
neutral.
5. The panelboard is restricted to 42 overcurrent devices in
an enclosure.
5. Calculate the percentage of overcurrent protection devices
rated 30 amperes or less
6. Determine if the Panelboard is required to be protected by
either an integral main or by the feeder circuit overcurrent
device.
2
© 2008–2010 Schneider Electric All Rights Reserved
0100DB0708R01/10
01/2010
© 2008–2010 Schneider Electric All Rights Reserved
Lighting and Appliance or Power Panelboards
3
Lighting and Appliance or Power Panelboards
Electrical Shortz
For More Information:
0100DB0708R01/10
01/2010
For more information see the following references:
2005 NEC® Article 408
UL Standard 67
Visit the Schneider Electric North America Codes and Standards Electrical Shortz website:
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“Electrical Shortz” are produced by the Schneider Electric North America Codes and
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