NFPA 70E

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rodneyl

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We are builders of industrial packaging type machinery. A good customer of ours has asked if we comply with NFPA 70E, in particular Arc Flash. We are unsure how to calculate for Arc Flash and what is involved with compliance. Can anyone make some suggestions, or possibly guide me to some info on this topic? Most of our machines are fused with "J" class fuses at 30 amps or less. We typically don't know what the upstream feed to our machines is or where it comes from. One of our Electrical Supply vendors has indicated that the burden falls on the customer, not on the machine builder. I have seen viewing windows and external control access ports. These devices are touted to "reduce the risks of arc flash explosions", is this enough?

Any help would be greatly appreciated.
 
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rodneyl

Member
Re: NFPA 70E

Thanks for the info, it was a helpful start. I do not know what the bolted current available is to our equipment though. The customers provide the power drops at installation of the equipment.
 
steve66

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Re: NFPA 70E

The Arc Flash energy available is going to depend mostly on the customers distribution system.

I also think this is up to your client to determine.

BTW, with 30A fuses, and I assume you are at 480V or less, the arc flash energy on the load side of your fuses would probably be pretty small, no matter what type of distribution it is connected to.

Steve
 
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MJJBEE

Member
Re: NFPA 70E

Originally posted by steve66:



BTW, with 30A fuses, and I assume you are at 480V or less, the arc flash energy on the load side of your fuses would probably be pretty small, no matter what type of distribution it is connected to.

Steve
Click to expand...
I agree do a calculation. It is totaly dependent on the avaible fault current of the supply. Remember that arc flash is dependent on the square of the clearing time. My example is when you take 480 and step it down to 240 via a small transformer (30 kVA) you can get an arc flash at level 3. This is because of the current limiting of the transformer.

The customer will have to do the calculation because you can't get the details of their system.
 
zog

zog

Senior Member
Location
Charlotte, NC
Re: NFPA 70E

There are some good training programs out there for 70E compliance, do a websearch for NFPA 70E Training, some courses are even availabe on webex,internet based live training.
 
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jim dungar

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Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Re: NFPA 70E

You as a manufacturer can not do anything to comply with NFPA70E.

NFPA 70E is about ELECTRICAL SAFE WORK PRACTICES not just about arc-flash. Safe work practices are defined by each company not by the standard.

Arc flash incident energy is totaly dependent upon the amount of available fault current at the point of the arc and the length of time the arc exists. Do not blindly trust fuses. Most fuses will not significantly reduce the arc flash incident energy unless they enter their current limiting range, which is often unlikely to occur if the available fault current is less than 10kA.

The difficulty in using generalized arc-flash PPE selection tools is highlighted by Bussmann's statement "Actual results from real arc-flash incidents could be different for a number of reasons, including different (1) system voltage, (2) short-circuit power factor, (3) distance from the arc, (4) arc gap, (5) enclosure size, (6) fuse manufacturer, (7) fuse type, (8) orientation of the worker, (9) grounding scheme, (10) circuit breaker manufacturer, (11) circuit breaker type, (12) circuit breaker settings, and (13) circuit breaker condition."

Remember electricity can kill, please use all of NFPA 70E not just the few pages related to arc flash.
 
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