2023/2/10 下午3:43
409.110 Industrial Control Panels. Marking.
409.110 Industrial Control Panels. Marking.
NEC Section 409.110 provides marking
requirements for industrial control panels. Buying a
listed industrial control panel ensures that the control
panel will have the appropriate markings. In the
event that an industrial control panel is field
constructed, such as a 12 X 12 box with an overload
relay and a push button, NEC 409.110 requires
seven different items to be marked on the control
panel. Item 4 can be easy or may require a bit of
homework in order to pass inspection.
Section 409.110 item (4) requires the industrial
control panel to be marked with the short-circuit
current rating (SCCR) of the control panel unless the
control panel contains only control circuit
components. There are two methods permitted in
409.110(4) to determine the SCCR:
1. Use a listed and labeled control panel that will
already be marked with the SCCR as part of
the product listing requirement.
2. Determine the SCCR of the control panel using
an approved method and mark it on the
control panel. NEC Article 100 defines the term
“Approved” as “Acceptable to the authority
having jurisdiction” (the inspector).
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Industrial control panels are required to be
marked with their SCCR.
The inspector may or may not want to be
responsible for allowing item 2 above since it leaves
liability in the hands of the inspection agency. The
informational note mentions Supplement SB in UL 508A as an example of an “approved” method.
The city inspector will generally not have a copy of the standard in order to know what Supplement
SB actually says.
The method mentioned in UL 508A Supplement SB can be quickly summarized as follows:
Determine the lowest SCCR of any individual component in the control panel.
Determine if any current limiting devices are protecting the control panel.
Mark the control panel with the SCCR based on the two items above.
See the actual NEC text at NFPA.ORG for the complete code section. Once there, click on
the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).
2014-2017 Code Language:
409.110 Marking. An industrial control panel shall be marked with the following information that is
plainly visible after installation:
(4) Short-circuit current rating of the industrial control panel based on one of the following:
a. Short-circuit current rating of a listed and labeled assembly
b. Short-circuit current rating established utilizing an approved method
Informational Note: ANSI/UL 508A, Standard for Industrial Control Panels, Supplement SB, is an
example of an approved method.
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2023/2/10 下午3:43
409.110 Industrial Control Panels. Marking.
Exception to (4): Short-circuit current rating markings are not required for industrial control panels
containing only control circuit components.
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409.110 Industrial Control Panels. Marking.
Below is a Real Question from our Electrical Continuing Education Courses for Electrical
License Renewal:
Which of the following is true of an enclosed industrial control panel containing only
control circuit components?
A: If it is listed, it will not be marked with a SCCR.
B: The required SCCR marking is only permitted for a listed assembly.
C: The SCCR marking is required for all control panels, regardless of what is inside them.
D:
The SCCR marking is not required for a control panel with only control circuit
components.
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