Multiwire Branch Circuits
Summary<: 2008 NEC requires a common handle tie or multi-pole breaker.
The 2008 NEC has a new requirement for multiwire branch circuits. The new requirement is for a common handle tie or multi-pole breaker rather than separate single-pole breakers. For example, devices that are wired with a common or shared neutral can no longer be served from single phase breakers. The breakers must have a handle tie or be a mult-pole breaker. The motivation for this added requirement in the NEC is to assure that all the energized conductors which may be present at a device or outlet box are degenergized during maintenance or fault.
So as a designer, what do you show differently on the plans? One approach is to consider this just a code issue that the electrician must address. However, the practical issue is the purchasing of the breakers. If the proper mult-pole breakers are not purchased, then the only means of being code compliant is to field install handle ties. Some plan reviewers have begun looking for the panel schedules to indicate the multi-wire branch circuits. Design Master will have this feature incorporated in the next release.