As I mentioned in another thread I was recently taking a course that is required for any worker who works on/near high voltage equipment. During the 2 day course I heard different stories from fellow participants about their past work practices regarding the frequency of working on energized equipment. For myself work practices have changed dramatically in the past few years and I seldom work, for example, in a 120/208 panel that is energized. If I do and for example I am changing out a breaker in a panel that for some reason can not be de-energized then I now wear the appropriate PPE which wasn't the case before.
Therefore, I would say the percentage of time that I spend working on energized equipment has dropped from about 50% to 5%.
What about some of you?
This rule was adopted as a direct result of the death of 'Red' (his nic) -- at the time employed by ##### my old company.
I spent one-day, and only that one-day, working with Red.
He was an extremely popular apprentice that every foreman wanted on their jobs.
He died working on a Rayco NEMA3R Service box 800A 208Y120V -- IDENTICAL to one I worked on earlier -- for the same contractor and same developer-owner-customer.
When faced with the IDENTICAL requirement to land a neutral on that Rayco bus, I insisted that the panel be killed. The geometry and dimensions made it quite impossible to land a neutral with the hot bussing so close. (REALLY tight)
The Super on my job was the same man who was the super on Red's job. (!) In fact, the same developer-owner-customer was building a clone of 'my' warehouse when Red died.
I'm going to leave out the ugly specifics -- other than to say that Red should NEVER have been left to work a hot panel solo -- and that if requested, the Super had no qualms about killing all Service power -- when asked.
The job site was within one-hour's driving distance from Sacramento. So EVERY heavy weight Cal OSHA inspector flew down the freeway from state HQ.
Then my General Superintendent (and best buddy) and the owner (license holder) were absolutely grilled for a full day.
Cal OSHA came out with a safety directive within days.(!)
ALL of the foremen were given the new marching orders.
The owner-contractor hired on Red's widow -- as an office staffer -- for the rest of her days. She'd never held a job before in her life. (A very nice lady, BTW.)
This tragedy colored all of the other Sacramento based electrical contractors. None now permit 'hot' work around panels unless it can't be avoided. In which case, the tradesman has to go the full route.
The 'California rules' were adopted at the very next opportunity by the NPFA.
It's now accepted that 'hot' work -- as previously done -- is, in fact, unnecessary. It doesn't even pencil out as cheaper or quicker. No-one dares work around hot bussing at the same speed they would if it were dead cold.
I have to work on energized equipment almost 100% of the time, but as a Testing Engineer. I troubleshoot equipment that doesn't always work right or at all when it's on, but never works when it's off. I usually don't work on more than 120VAC or 134VDC control circuits, but I might be fairly close to 480VAC or 600VDC. Once I find a problem, we remove power to make repairs. We wear 8 Cal/cm^2 arc flash rated clothing but have the 40 Cal moon suits available if needed. Our 2 day Arc Flash Calculations course was last week.
Yep, I thought I would call it what it is instead of what it's called. People tend to refer to our control power as 125 VDC. It's really a string of 60 lead/calcium cells being floated at 2.23 VPC so we set the chargers to 133.8 VDC. It's higher than that during a 72 hour EQ cycle. I would not use that number during any future attempt at an arc flash study because the charger would immediately switch to its current limit servo loop during a fault.
Joe
If you work on batteries, you work it hot, period.