Arc Flash Study Requirement

[faresos]

Hello Everyone:

Does the NEC require us to perform an Arc Flash Study for the entire facility if a an existing generator (1000KW) is being replaced by larger one (2000KW)? There are additional mechanical loads are being added to the new generator. We will need to add another main breaker to the main service switchboard to accommodate this change. New equipment such as ATS's/switchboard/dist panels will be added. My thought since the main service source (utility transformer) is not being changed, which delivers the worst fault current, we only required to do the arc flash study for the new equipment added.

Any thoughts?

Thanks,

 

[jim dungar]

The NEC never requires an arc flash study. Arc flash labeling, showing PPE requirements, is required by OSHA and NFPA 70E.

The worst case/highest fault current values do not always produce the highest arc flash incident energy, due to protective devices operating in their instantaneous region. It is quite common that lower levels of fault current, like from a generator, can produce higher incident energy.

I would definitely have the arc flash study redone including the new generator and emergency system circuits.

 

[faresos]

The NEC never requires an arc flash study. Arc flash labeling, showing PPE requirements, is required by OSHA and NFPA 70E.

The worst case/highest fault current values do not always produce the highest arc flash incident energy, due to protective devices operating in their instantaneous region. It is quite common that lower levels of fault current, like from a generator, can produce higher incident energy.

I would definitely have the arc flash study redone including the new generator and emergency system circuits.

Thanks Jim.
So NEC section 110.16 (Arc- Flash Hazard Warning) which refers to section 110.21(B) requires arc flash hazards labels but not necessary the labels need to indicate incident energy value or PPE type, correct?

 

[tom baker]

Thanks Jim.
So NEC section 110.16 (Arc- Flash Hazard Warning) which refers to section 110.21(B) requires arc flash hazards labels but not necessary the labels need to indicate incident energy value or PPE type, correct?

Yes.
The NEC is an installation standard, not a safety standard.
And just like NFPA 70, 70E needs to be adopted. In WA we have not adopted 70E, as we are under WISHA, not OSHA.

 

[faresos]

Yes.
The NEC is an installation standard, not a safety standard.
And just like NFPA 70, 70E needs to be adopted. In WA we have not adopted 70E, as we are under WISHA, not OSHA.

Thanks Tom

 

[tom baker]

I need to clarify about 70E. If your workplace is under OSHA, my understanding is OSHA uses 70E, but it may not be the current 70E.
Not all states are under OSHA. OSHA allows an equal safety standard, like WISHA.

 

[paulengr]

I need to clarify about 70E. If your workplace is under OSHA, my understanding is OSHA uses 70E, but it may not be the current 70E.
Not all states are under OSHA. OSHA allows an equal safety standard, like WISHA.

Arc flash is under the general duty clause for utilization equipment. For generation, transmission, and distribution it falls under 1910.269. Not 70E, not NESC. They have their own rules.

Under the general duty clause OSHA requires protection against recognized hazards. They can’t and won’t mandate any specific Code. You can make up your own but it’s a stronger argument to say you followed a consensus safety standard (Code) since you don’t have to make any scientific claims.