Arc flash hazard analysis 240v

[Davebones]

According to NFPA 70E ( 130.3 ) exception no. 1 .We have a 115 kva 480V to 208V 3 Phase transformer that feeds 4 panels . Am I correct in understanding a arc flash analysis does NOT have to be done ?

 

[jim dungar]

Am I correct in understanding a arc flash analysis does NOT have to be done ?

You are correct, no analysis needs to be done. However, it does not mean these locations can be ignored.
This exception does not 'overule' the requirement that the equipment must be labeled with the PPE requirements or the incident energy.

 

[ghostbuster]

You are correct, no analysis needs to be done. However, it does not mean these locations can be ignored.
This exception does not 'overule' the requirement that the equipment must be labeled with the PPE requirements or the incident energy.

Do you mean ,you should use only the tables to determine PPE requirements , if you are not doing an analysis.

 

[jim dungar]

Do you mean ,you should use only the tables to determine PPE requirements , if you are not doing an analysis.

IMHO, the tables should not be used for general day-to-day activities, a system study should be performed.

But there are many people that feel, the decision by IEEE to not perform calculations below 240V on transformers <125kVA and the predominant task table rating of HRC=0 for 240V locations means, the secondary of these transformers never exceeds HRC=0.

 

[Hugh_Hoagland_e-Hazard]

208V systems

208V systems

John is right. The standard does say you don't have to do them BUT there is a TIA on the NFPA 70E site right now proposing to remove that language. If you do a 208V system you will usually find that they are greater than the tables in energy levels. We always recommend doing arc flash calcs on 208V systems since they can easily become a 480V 3-Phase arc fault in most equipment configurations.

Hugh Hoagland

 

[zog]

John is right. The standard does say you don't have to do them BUT there is a TIA on the NFPA 70E site right now proposing to remove that language. If you do a 208V system you will usually find that they are greater than the tables in energy levels. We always recommend doing arc flash calcs on 208V systems since they can easily become a 480V 3-Phase arc fault in most equipment configurations.

Hugh Hoagland

Here is the TIA Hugh is refering to, they don't put stuff up there that is not going to change. Hmmmm, wonder what ll the people that used that execption are going to do now?

Welcome Hugh, glad to see you here.

 

[jim dungar]

....208V systems since they can easily become a 480V 3-Phase arc fault in most equipment configurations.

How is a 208V system going to "become" a 480V arc flash in most equipment?

Hmmmm, wonder what ll the people that used that execption are going to do now?

The same thing they did when HRC= -1 and the exception for less than 10kA disappeared.

And isn't the TIA still in the proposal stage?