Re: Article 210.4(B) - 2008 NEC;
Interpretation of Article -VS- "Intent" of the Article.Looking for input from anyone in the Design / Applications / Management areas, and especially from Inspectors, Plans Examiners and Code Consultants, regarding the Long-Winded Post below!
On a very large, and very complex Project we have (out of State, not in California), the DBS (Building Department) just adopted the 2008 NEC.
Adopted in entirety, with no amendments, in effect September 1st, 2008.
I Designed / Engineered the areas within "Our Scope Of Work" (there are 3 other E.C.s on this Project - told you it is a big project!), and submitted the Plancheck Set in late August, 2008.
No P/C revisions were requested, nor were any Bulletins or other documents issued by the DBS.
Panelboards, Switchgear & Transformers were supplied and installed by another E.C. (panels, gear, transformers, devices and feeders not in our scope / N.I.C.).
In July, 2008, I submitted Panel Schedules describing the Circuitry + Devices we needed for our Scope, to the Electrical Consultants hired by the Client.
This Firm is to supply the Panels, Gear, Devices and Transformers to the installing E.C.(s) of the project.
Work began on the Project September 8th, 2008, and I am Project Manager for this job.
Now to the point!!!
The DBS is interpreting 210.4(B) to be for _ANY_ Multiwire Branch Circuit - not simply where a MWBC terminates to a single yoke, or in a single piece of Equipment.
Simply stated, all the Multi Wire Lighting Circuits I have Designed on this Project, will require Multipole Common Handle Tie Circuit Breakers, even though no single Fixture will have 2 or more Circuits terminating inside them.
I contacted the DBS to verify the interpretation, and they confirm the above interpretation.
Am I missing the point of the Article, or is this a mis-interpretation by the DBS?
As I understand (and interpret) Article 210.4(B), it's intent is to eliminate the hazard of One (or more) Ungrounded Conductors being left energized on:
* A Single Yoke Device - such as a Receptacle,
* In a single piece of Equipment - such as a Lighting Fixture, having Ballasts connected to 2 individual Circuits;Example:
1 Ballast from switched Lighting Circuit on CKT #10, 1 Emergency Battery Back-Up Ballast connected to unswitched Lighting Circuit on CKT #12
If separate 1 pole devices were used for the above listed Circuits, a _QUALIFIED_ Person working on the Device / equipment may inadvertently leave one or more 1 pole OCPDs closed, for the MWBC feeding the item, introducing a Ground Fault hazard at the item.
Risk of L-G Ground Fault (shock, short circuit/sparks flying, or both) is dramatically reduced at the single device / equipment by the use of a Multipole or Common Handle-Tie OCPD.
This _DOES NOT_ include Junction Boxes with MWBCs, or multiple Outlets / Equipment where MWBCs will run through, but only a 2-wire Circuit (L-N) terminates on the device, or at the equipment.
This is really a problem for this particular project, as the Lighting Circuits use Lighting Contactor type Circuit Breakers (read: $$$).
Additionally, one of the Lighting Panels is connected via ATS to the Emergency Power System - and the Night Lights / Emergency Lights are derived from that Panel, along with several General Lighting Circuits for common areas.
The "Switched" Gen. Ltg. circuits from that Panel include an Unswitched circuit, for Night Lights / Emergency Lights in the common areas.
These are MWBCs.
A 3 Pole device with Lighting Control feature, will open the unswitched circuit, leaving the Em. lighting to run solely on Battery Back-Up power for > 8 hours.
This, of course, will drain the Batteries in less than 120 Minutes - every day, leaving the egress areas unlit.
Looking for input from anyone in the Design / Applications / Management areas, and especially from Inspectors, Plans Examiners and Code Consultants.
Thanks in advance.