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PostPosted: Mon Nov 17, 2008 12:18 pm 
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Joined: Mon Jun 02, 2008 11:58 am
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Location: Charlotte, NC
Have you looked at ANSI/IEEE C37.20.7-2007?

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PostPosted: Mon Feb 02, 2009 3:35 pm 
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Joined: Thu Oct 18, 2007 7:10 pm
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Location: NW USA
Zog wrote:
(Reposted from feed blitz)

A recent article in the NFPA Journal discusses the thorny question of whether, and in what circumstances, personal protective equipment should be worn when there are no live, exposed electrical parts. Technically, when there are no exposed parts, there is no flash protection boundary—but there may still be a risk of injury. Equipment doors can be blown open and panels blown off by an arc flash explosion, and hot gases can escape through louvers or cracks and cause burns.

In a facility using the PPE tables provided in NFPA 70E, there are a few instances where PPE is required even though no live parts are exposed. For instance, Table 130.7(C)(9)(a) lists the required PPE for "Circuit breaker (CB) or fused switch operation with doors closed" as hazard/risk category 2. However, even for facilities which do not rely on the NFPA 70E tables, safety-consciousness will often suggest wearing more PPE than is explicitly required.

In the 2009 edition of NFPA 70E, a new fine-print note will be added, which will state in part, The collective experience of the task group is that in most cases closed doors do not provide enough protection to eliminate the need for PPE for instances where the state of the equipment is known to readily change, i.e. doors open or closed, rack in or rack out.

While a fine-print note is not a formal requirement, arc flash safety isn't about following the letter of the law. True safety consciousness requires taking appropriate steps to minimize all hazards—and wearing PPE is often one of those steps.

Are there any ad-hoc committees overseeing the code writing panels? It seems they have a license to close facilities and nobody is speaking up. IEEE PCIC 94-32 addressis some of arc containment in non arc rated gear (albeit 460V MCC's) yet that doesn't seem to be considered in the 2009 NFPA 70E. It seems unlikely that large manufacturers would continue to market switchgear with operating devices on the faces that are illegal to approach unless special PPE is worn, yet that is the interpretation.

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