Fluorescent luminaires are sometimes serviced while energized to avoid removing illumination from an area. This includes the full replacement of ballasts, often requiring individuals to work while on ladders, allowing limited mobility and/or ability to react to shock incidents where the worker may come into contact with energized parts. One leading cause of fatalities for electricians is electrocution while working on 277-volt lighting systems. When the electrician gets to the wire nut with three white wires (neutral), the thought is that these are grounded conductors and aren't hazardous.
In fact, these white wires carry the unbalanced load current from all phases of the white wires. When the electrician opens the wire nut and gets between two of the white wires, shock or electrocution can result.
New requirement - Article 410.73(G) - is an effort to provide safer conditions for those performing this type of service.
Disconnecting Means for Electric-Discharge Lighting Systems—has been added. This article requires a disconnecting means to be installed either inside or outside the luminaire that can disconnect all conductors of the ballasts. The type of lighting equipment involved in this code include fluorescent luminaires that use double ended lamps and/or contain ballasts.
Included are (5) five exceptions that cover installations or conditions where variations of the rule are needed or where it is not considered practical to apply this requirement, such as in emergency lighting ,and in hazardous locations.
The article reads as follows:
410.73 (G) Disconnecting Means: Other than dwellings and accessory structures, all indoor locations with fluorescent lighting (fixtures) which contain ballast(s), use lamps that can be serviced in place or reballasted luminaries that are supplied from multiwire branch circuits and contain ballast(s) which can be serviced in place shall have a disconnecting means either internal or external to each luminaire (fixture), to disconnect simultaneously from the source of supply all conductors of the ballast, including the grounded conductor if any. The line side terminals of the disconnecting means shall be guarded. The disconnecting means shall be located so as to be accessible to qualified persons before servicing or maintaining the ballast. This requirement shall become effective January 1, 2008.
Exception 1: A disconnecting means shall not be required for luminaires (fixtures) installed in hazardous (classified) location(s).
Exception 2: A disconnecting means shall not be required for emergency illumination required in 700.16.
Exception 3: For cord-and-plug-connections, an accessible plug and receptacle or an accessible separable connector shall be permitted to serve as means for disconnecting.
Exception 4: A disconnecting means shall not be required in industrial establishments with restricted public access where conditions of maintenance and supervision ensure that only qualified persons service the installation by written procedures.
Exception 5: Where more than one luminaire is installed and supplied by other than a multiwire branch circuit, a disconnecting means shall not be required for every luminaire when the design of the installation includes locally accessible disconnects, such that the illuminated space cannot be left in total darkness.
By installing a disconnecting means for each ballast allows the building owner a superior safeguard in preventing eloctrocutions during servicing. For a small office building, cost may become an issue and this scenario would not affect the budget. However, a high-rise or commercial building, installing a disconnect at each ballast becomes very costly. This is when the exceptions have their merit. For example, Exceptions 3 and 5 can keep the area safe for servicing while staying within budget. Exception 3 allows the installation of a plug type disconnect, so that the individual ballast can be unplugged and serviced safely. Exception 5 allows multiple luminaires to share one disconnect or plug. Now, a design with 50 luminaires can perhaps have two disconnects means or plugs, having every other luminaire or a series on one branch, and the others on a separate branch. This way only one branch would be disconnected at a time to service the illuminated space and not be left in total darkness when doing so.
This new requirement will allow servicing electricians to de-energize ballasts without removing light from the affected work area. This way they can safely change out the ballast without being exposed to any unnecessary electrocution hazard(s). This change has been given an effective date of Jan. 1, 2008, to allow manufacturers time to develop products for this application and allow sufficient time for the industry to prepare to include switches for this type of lighting.
