OSBORNE, R.: The consensus among panel members is that, for those
devices requiring connection to a grounded conductor, it is imperative that a
grounded conductor be available at the device location. This position is in full
alignment with Article 250 and a long-standing position held by panel 5.
It should be noted that the panel statement is consistent with past decisions by
panel 9, which concluded that it is the responsibility of the installer to ensure
the appropriate conductors are provided at the device box. However, the panel
fails to acknowledge that, without a grounded conductor in a switch box being
mandated in Article 404, improper use of the equipment grounding conductor
is commonplace when these products are installed retroactively.
It appears that there is a potential correlation issue in that the requirements in
Article 250 cannot be satisfied by the decision by panel 9 not to address
grounded conductors in switch loops. The TCC needs to take a closer look at
this proposal and accompanying comments as they relate to satisfying the
requirements of Article 250 to determine if the Code is providing adequate
guidance regarding the installation of devices requiring the use of the grounded conductor.
The reality is that control devices which need a return path for inboard control
circuitry are becoming much more prevalent in both residential and commercial
installations. As the use of these devices increase, the likelihood that
unintended current will make its way onto equipment grounding conductors
increases. Additionally, proliferation of these devices also increases the
likelihood that, based on the cumulative effects of control currents, higher
levels of unintended current flow will be present on the equipment grounding
conductor.
Acknowledging the ever-increasing use of these devices, the panel should
have concluded that it is time to readdress this issue. A step in the right
direction would be to ?Accept in Principle? the proposal, with additional
language that limits the new requirement to only those installations where it is
impractical to add the grounded conductor at a future date. The reality of such
an exception is that, in most installations where a cable wiring method is used,
the grounded conductor will be required. This would include the majority of
residential applications where the homeowner, unaware of the safety issues
related to current flow on the equipment grounding conductor, would have a
grounded conductor available at all switch locations which control lighting
loads. This exception would have the opposite affect in most commercial
applications where raceways are employed and trained electrical workers
appreciate the needed for a grounded conductor. It is in these applications, due
to the presence of a raceway, that the installer has the ability to install the
required conductor without damage to the building structure or building finish.
To address the submitters concerns, the following text is offered for
consideration:
Add text to read as follows:
404.2 Switch Connections
(C) Switches Controlling Lighting Loads. Where switches control lighting
loads supplied by a grounded general purpose branch circuit, a grounded circuit
conductor shall be provided at the switch location.
Exception: Grounded conductors shall not be required in installations where it
is possible to install conductors into the device boxes without damaging the
building structure or building finish.
RUPP, B.: Occupancy sensors are permitted by UL773A to have a current of
up to 0.5 ma on the grounding conductor. This is allowed because the operation
of an occupancy sensor requires a low level standby current. The standard
permits this current on the grounding conductor because in a typical installation
there is no grounded circuit conductor in the switch box which can be used as
the return conductor for the standby current. An occupancy sensor can be
installed in any switch location. It is impractical to expect the customer or
installer to anticipate all instances where an occupancy sensor will be installed.
Accepting this proposal will insure that a grounded conductor is available at all
switch locations which will allow occupancy sensors to use the grounded
conductor for conducting standby current instead of using the equipment
grounding conductor.
Comment on Affirmative:
HARTWELL, F.: On another proposal (9-60) this panel member took
considerable pains to point out the essential requirement of electrical inspection
as a component of the electrical safety system. This proposal provides a perfect
opportunity to bring in the third component, that of a set of product standards
that assure that products used in electrical systems have been manufactured to
work in the context of the NEC, which is the installation code. With the correct
markings and instructions, these products will be selected and installed, and the
systems designed, so the equipment grounding system will not become a
routine circuit conductor. It was established at the panel meeting that the
applicable standards are already in the process of modification in this area.
