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 IAEI News>Focus on the Code >CMP-11
Question
1. Is there
any information on manufacturers that are building to
the requirements listed in 440.65? Is anyone enforcing
it? — G.G. Answer 1. NEC 440.65 requires factory installed leakage current
detection and interruption (LCDI) or arc-fault circuit-interrupter (AFCI)
protection for single-phase, cord-and-plug connected room air conditioners.
As of June 2002, there are no listed air conditioners that employ either
protective technique. The UL standard for room air conditioners is being
revised to require LCDI or AFCI protection. The revised standard may be
issued yet this year. A revised standard normally permits manufacturers to
take up to one year to make the necessary revisions to their product. The National Electric Code recognizes that code changes
may initiate changes in electrical appliances and utilization equipment. The NEC acknowledges that this process may not be complete by the time the
authority having jurisdiction (AHJ) has adopted the newest version of the
Code. Section 90.4 gives AHJs the ability to approve air conditioners listed
to the current standard and installed to the most recent previous edition of
the Code. —Tom Garvey, CMP-11. | Return
to top | Question
2. I am very confused on what inspectors of
Riverside County, California, are asking for on A/C condensers (breakers
size). For example, if the condenser plate reading has a minimum breaker
size of 24 amps, and a maximum breaker size of 35 amps, and I install a
30-amp breaker size, am I in the wrong? Inspectors are telling me that I
should go to the max on the breaker. Are they correct? I cannot find this
section in the NEC 1999. — F. A. Answer 2. This
is not a violation of the Code unless the nameplate of
the unit specifies a minimum size fuse or circuit breaker
greater than 30 amperes. Section 440.4(B) in the NEC 2002 applies to air-conditioning equipment that contains a
hermetic refrigerant motor compressor and other equipment such
as a fan motor. The Code does not require manufacturers
to list minimum size overcurrent protective device sizes on
the nameplate. The nameplate must only indicate the maximum
rating of the fuse or circuit breaker. If the manufacturer elects to specify a
minimum size device on the nameplate, NEC 110.3(B)
would require the installer to abide by the nameplate
information. — Tom Garvey, CMP-11. | Return
to top | Question
3. I have a question related to 430.74, which
states, "Motor control circuits shall be arranged so that
they will be disconnected from all sources of supply when the
disconnecting means is in an open position." This is an industrial installation in which
we have starter panels feeding multiple pieces of equipment in
a process from the panel. The system is controlled by a PLC.
The main disconnect switch on the panel interrupts the 480 VAC
to the panel but the 120 VAC to the PLC I/O cards comes from a
different supply and is not interrupted by the main disconnect
switch. When 430.74 refers to the disconnecting
means does it mean the panel disconnect, the controller
disconnect required in 430.102(A), or either? By motor control circuits does the NEC mean
just the wires to the coil, or are the status contacts from
the aux contact included? Does the NEC require that the main
disconnect for a panel disconnect all sources of supply inside
that panel? I also have some questions related to
E-stop circuitry. This is not covered by the NEC. Do
you have any recommendations on good sources of information? I
have tried NFPA 79 and some European standards but I am not
sure if these are "binding," other than as good
engineering practices. I need to have definitive documentation
to get the money to make changes. —M.K. Answer 3. Your
first question refers to the requirement for a disconnecting
means for the motor control circuit. The requirement is found
in 430.74 of the 2002 NEC. The main disconnect can
serve as the disconnecting means for power and control
circuits for all of your starter panels. An acceptable
alternative is the disconnecting means for an individual
starter panel. The former option is very common for industrial
processing equipment. Since the motor controllers act together
in a coordinated fashion, often Exception 2 to 430.102(A) is
employed. This exception permits a single disconnecting means
for coordinated controllers operating multiple parts of a
single machine or process. Your second question refers to the
definition for a motor control circuit. You ask if status
signals are part of the control circuit. Status signals
are not part of the motor control circuit. I refer you to
Panel 11’s action on proposal 11-49 of the 2005 NEC Report on Proposals. The panel rejected a revised definition
that would have included status signals as a type of motor
control circuit. Your last question asks if the main
disconnect must disconnect all sources of supply inside that
panel. No, multiple disconnects are permitted to make up the
disconnecting means. Please note that if a separate disconnect
is used for the motor control circuit, the control circuit
disconnect shall be immediately adjacent to the supply circuit
disconnect. This requirement is found in the last sentence of
430.74(A). This requirement is similar to 5.5.3 of the 2002
NFPA 79. NFPA 79 is more stringent than the NEC in this
respect. Section 5.3.5.4 indicated that where circuits are not
disconnected by the supply disconnecting means additional
safety provisions such as warning labels are required. You also indicated that you were looking
for advice on E-stop circuitry. I would ask that you contact
your company’s safety officer or your local OSHA compliance
officer. They may have a strong opinion on NFPA 79 being
"binding" in your facility. —Tom Garvey, CMP-11 | Return
to top | Question 4. Section 430.102(A) states, “An individual disconnecting means shall be provided for each controller and shall disconnect the controller.” (The controller is a set of contacts controlled by a magnetic coil or similar device, disconnecting its control power or all potential available within the environment of the controller enclosure.) Does this mean an additional disconnect is needed for control power if separate from the motor power source? (see figures 1, 2, and 3). If exceptions listed under 430.102(B) are prevalent, do they apply to 430.102(A)? — B.G. Answer 4. Your question refers to the disconnecting means requirement of the motor control circuits, the controller and motor, using 430.102(A) as a reference. First, let us begin with NEC Figure 430.1 to discover the appropriate parts of Article 430 to reference. Part VI contains the “Motor Control Circuits” requirements, and Part IX, “Motor Disconnecting Means.” Part VI, Section 430.74(A) requires motor circuit conductors to be arranged so that they will be disconnected from all sources of supply when the disconnecting means is in the open position. The disconnecting means shall be permitted to consist of two or more separate devices, one of which disconnects the motor and the controller from the sources of power supply for the motor, and the others, the motor control circuits from the supply. Where separate devices are used, they shall be located immediately adjacent to each other. Three exceptions do not appear to apply to the information as given. Second, Part IX, Section 430.102(A) requires an individual disconnecting means that disconnects the controller to be in sight from the controller location. Section 430.102(B) requires a disconnecting means that disconnects the motor to be located in sight from the motor. This disconnecting means could be the same disconnect as required in 430.102(A) for the controller only if it is in sight from both the controller and motor. The exception to 430.102(B) permits the required motor disconnecting means to be out of sight of the motor under two conditions: (a) where being in sight is impracticable or introduces additional or increased hazards to persons or property; or (b) in industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure only qualified persons service the equipment. Therefore, review the figures from the drawing presented by the reader: figure 1 violates both 430.74 and 430.102; figure 2 violates 430.74; and figure 3 complies. This review is based on the given information and assumes conditions (a) and (b) of 430.102(B) exception are not applicable. You also inquired if the exceptions listed under 430.102(B) are prevalent, do they apply to 430.102(A)? These exceptions apply only to the heading under which they are located— 430.102(B), Motor—and not to 430.102(A), Controllers. I hope this answers your concerns. As always, it is suggested that one consult with the local authority having jurisdiction. — Tom Moore, CMP-11 — Return
to top — The views of the authors of Focus on
the Code and the editor are provided solely as a public service. yers. Nor are they intended to
represent a formal or informal interpretation of the NEC. |
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