Sometimes if you get a good pop, you get the taste of metal in your mouth. Or is that just me?

I don't recall ever having a metallic taste in my mouth. But as a kid there have been times while plugging something into a difficult to penetrate 120VAC outlet my fingers slipped off the body of the plug and slid down on the metal contacts. Probably as early as 7 years old when I got my first 120VAC shocking. I believe my father called it 115 volts. Every home is slightly different. I've had homes with voltages ranging from 110 to 125 VAC. The oddest voltage at the outlet I've ever found was 117.8 VAC. And MANY experiences with getting shocked. The dumbest shocking I took was when I was working on an outlet (120 VAC) with a metal screwdriver. The whole thing was metal. Being careful not to touch hot and ground at the same time with my left hand I grasped the LIVE outlet (which is why I recommend switching the breaker off before working on ANY electrical circuit) - with my left hand holding the outlet I took the all metal screwdriver in my right hand with the intention to tighten up the screw connection. As SOON as the metal screwdriver touched the screw I discovered my folly. I don't know about anyone else but I've ben known to work on live circuits fairly frequently. Paying close attention to detail can mitigate the chances of being shocked such as when I was working on the power supply of an amplifier. Being cautious to keep one hand away from all parts the other hand and tool touched live power. No shock yet. But I then rested my arm on the case of the amp. Got another lesson why you unplug equipment or shut off breakers. But I never learn.

I am a little more fearful of 240 VAC. I only have one outlet at that power for my table saw. I ALWAYS switch the breaker off before I do ANYTHING with it. I may be dumb but I'm not totally stupid. But clearly I could be a little smarter. You can be a lot smarter than me if you just turn the breaker off - or unplug the machine you're working on.

 

I am a little more fearful of 240 VAC.

Really? American 240V AC is only 120V to ground. It's not very likely that you'll touch the two opposite lives at the same time. Just as it's very rare to get a 400V shock from three-phase. Even if it's a three phase supply the most likely shock is 230V to ground. The oddest feeling is 108V DC from an emergency lighting system.
European sockets all have some means of preventing contact with the pins as the plug is being inserted and removed. France and Germany (and other Schuko countries) have a recessed socket, Britain, Italy and Denmark have partially sleeved pins. Schuko is an abbreviation of the German "schutzcontact" meaning "protected contact".

 

You WILL find in some office buildings, that they use 3-phase to feed lighting circuits, as that is 277 to common on each of the three legs. That is a trap for those who would add a requested 120 volt outlet in an office area. So it is important to verify voltages when working in buildings served by 3 phase power. My experience was that I discovered this before adding any connections, and the simple effort became a bigger project.
Also be warned that 277 volts will give a MUCH NASTIER SHOCK than 120 volts.
So in most shops that have 3-phase 480 for the bigger motors, the voltage to common is 277. There are a few exceptions that I have read about but not experienced.

 

You WILL find in some office buildings, that they use 3-phase to feed lighting circuits,

Most generally use a 208 3phase star secondary, = 3 120v legs to N for lighting.
Here in Canada, large industrial installations are 600v 3ph.

 

In my area it was 480, used in the delta arrangement for motors and as 277 star for lighting. At least the Fluke DMM said it was 275, close enough to 277.
At the same building, six months later, a crew installed new LED parking lot lights, without checking the supply voltage. The burned smell was still quite strong three days later when I stopped by.

 

In my area it was 480, used in the delta arrangement for motors and as 277 star for lighting. At least the Fluke DMM said it was 275, close enough to 277.
At the same building, six months later, a crew installed new LED parking lot lights, without checking the supply voltage. The burned smell was still quite strong three days later when I stopped by.

Sounds like an engineering Gaffe, who specs in 277v for lighting?

 

I was not involved with that at all. The place was a for-profit build in an office building complex and this was one of the later buildings, probably from the mid 1980's, when power was a big consideration. And the person I was doing the work for, had no power consideration skills at all. I did not need to do much besides phone network and computer network..After my regular 8 hour day engineering.
So he took the suites that were cheapest and I made the stuff work. And it al passed inspections. 277 volt lighting can use thinner wire and so that was a cost saver for the builder. I never said it was a good idea!

 

277V is the phase-to-neutral stage for 480V phase-to-phase, 277Y480. We use that for heavy industrial loads like semi production so facility lighting circuits can be spec'd without a transformer on a main buss. It's used because it's cheaper, more efficient when large lighting loads are charged on a mass scale per a schedule.
https://www.lightingdirect.com/277-volt-lighting/c31430?r=48&s=SCORE&p=1&categoryId=31430

 

Sounds like an engineering Gaffe, who specs in 277v for lighting?

I've known 277 was found in grocery store lighting. Back in the early 80's I serviced emergency lighting. Was then when I found out store lighting was 277. Like Mr. Bill said - back in the 80's. Early to mid 80's. Came across exit signs that were powered from 277. The ones I dealt with had capacitive drop to operate on 120.

 

And 277 will be a much nastier shock, much more than twice as nasty as 120. Evidently shock nastiness is not a linear function. Who would have guessed???

 

You can always ask DJT. He seems to know everything.

 

You can always ask DJT. He seems to know everything.