This week's question was provided by a member of the Arc Flash Forum community.

The phrases 50 Volts or More and Less than 50 Volts are used throughout NFPA 70E when defining the applicability of specific requirements.

This week's question is about the "Less than 50 Volt" language and NFPA 70E 130.5(D) Equipment Labeling (which does not mention the 50 Volt threshold).

If equipment does not have a label for whatever reason, it can sometimes lead to confusion over whether the equipment was missed in the study, was exempt or was omitted for some other reason.

Here is this week's question:

Do you label any equipment rated less than 50 Volts?
Yes
No

Please share your views with everyone! What information is listed - if any, what types of equipment less than 50 Volts are labeled or perhaps, no label at all. What are your practices for equipment that does not have a label?

Are you kidding me? Does a boat or golf cart or car battery need an arc flash label? If it says arc welder, doesn't the presence of an arc become sort of implied?

Sorry but at some point, common sense SHOULD prevail, or at least the prudence test.

Same with under 250V or under a reasonable incident energy threshold. At some point each site should document/declare a 'minimum' threshold including PPE and move on. Going around labelling anything under 50 V, let alone 250 V is a waste of time/money at worst, and over reaching at best. Marking 120 V panels is silly enough, but marking arc flash on a golf cart? Really? Next thing you know we'll follow Roberts suggestion of lowering the shock threshold to 28 V without documented fatalities except some suspect Chinese reports and start having to wear rubber gloves to handle CAT 5 cable!

I for one applaud 70E for not going too silly but the phrasing suggesting sites must PROVE a negative (arc flash does not pose a hazard under 50 V) while rejecting lots of public inputs for the same thing (no evidence of injury) is crazy and needs to be gone unless guidance as to such circumstances is documented.

I agree with Paul. The doorbell/buzzer does not need it even if it all exposed (parts counter buzzer)

We label "low voltage" panels,not with incident energy, but international electrical symbol and the highest voltage. We also include the voltage marking on the incoming and outgoing conduits. This labeling can help keep maintenance Team members from disregarding "non-labeled" panels and helps keep the confidence in the identification system; Ultimately helping Team Members make good decisions based on training and experience.
Regards,
Bill Doss
P.S.
We have over 2,500 panels (208 or 480 volts) and pieces of equipment that I personally track in our placarding program. We also have 100's of other single disconnecting means (208 or 480 volt) throughout our facility. Yes, hundreds of panels with >50volts

Statistically, many more injuries are caused by shock & electrocution, not the arc. There is a significant shock hazard at 50V. Hence, it makes sense applying warning labels highlighting the shock hazard to any electrical equipment rated less than 50V. I would consider using generic warning label same or similar to the one at <removed link to commercial website>

We are planning to label most all equipment with some type of label - we have 1000's pieces and every time something is operated - if there is a question - it causes a work stoppage. Besides it gives the opportunity to add information such as where the device is feed from and with the labels dated also designated that the device has been inspected and is assumed to operate properly.

One of our dilemma's is to whether or not to label junction boxes - in designs over the years I have used a distribution block in a tough above a bank of panels - the distribution blocks have exposed parts and pieces. But if we were to stipulate that all junction boxes are to be label that back log would be enormous. So we decided when we come across a situation that exposed parts and pieces do exist we will label that equipment as well.

If you incorrectly apply the IEC resistance which is voltage dependent it looks like 50 V is a hazard but it is identical to IEEE 80 and similar values when voltage is considered. Roberts went further by assuming incorrectly that human resistance is uniform internally and missed that most of the voltage drop is from skin. Also many standards ignore the upper time cutoff after which fibrillation is just not going to happen, typically taken as 5 seconds. This yields no hazard at 50 V or below. Second, there are ZERO recorded fatalities under OSHA at or below 50 V. There is some extremely vague and questionable data from China that gives a wide range of voltages that Roberts uncovered but given a lack of credible evidence from the first world, it looks extremely unlikely that a fatality is possible below 50 V. At best, some Australian companies are claiming concerns about open circuit voltages of welders that are above 50 V but then immediately drop down to well under 50 V. Telecom PoE and most telecom equipment uses a 48 V standard, well below the old 90 VAC ringer voltage that used to be available on the black/yellow wires decades ago. Again, no fatalities despite extremely poor shock protection practices of telecom workers. So I'm not seeing the significant hazard of electrocution at 50 V or below.