ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 2 3 [All]   Go Down

Author Topic: Switched Neutral  (Read 6786 times)

Frank DeWitt

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 995
    • LBP DI Box
Switched Neutral
« on: June 10, 2014, 11:18:11 pm »

I'm working way up in the clock tower of a old church doing some mechanical work to the old clock and the light switch is flakey.  about 10 tries to get it to stay on.   I need to come back in a week with some more parts so I tell the church about it.  Would I change the switch when I am up there?  It's going to be hard to get an electrician to climb 5 ladders to change a switch.  also, there is another switch at the foot of the tower that kills all the power to the tower.  OK,  Turn off the power, climb the tower, check everything, trust nothing.  SWITCHED NEUTRAL ARE YOU KIDDING ME.

Fixed it, no one was hurt.

This stuff really does happen.
Logged
Not to Code

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3355
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Switched Neutral
« Reply #1 on: June 11, 2014, 12:09:50 am »

SWITCHED NEUTRAL ARE YOU KIDDING ME.
This stuff really does happen.

Many (or maybe even most) K&T wiring used switched neutrals all the time. And you have to be especially careful when you find new Romex installed in a old building that once had K&T. That's because sometimes an "electrician" would splice Romex onto the existing K&T wiring inside the walls to save money and fool the inspectors. And, of course, that's where RPBG (Reverse Polarity Bootleg Ground) outlets are born.

Frank - How did you find the switched neutral? Did you measure first or were you "surprised"?  I've found them both ways, I'm sorry to say.
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Lyle Williams

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1556
Re: Switched Neutral
« Reply #2 on: June 11, 2014, 04:29:00 am »

The temporary construction wiring standard down here in Australia now requires all switches and breakers to be double pole.  A countermeasure against crazy wiring practices.  Down here the construction standards are the most up-to-date (a decade+ ahead of the shows&carnivals standard).  It also seems to anticipate/address more poor practices than the other standards.
Logged

Frank DeWitt

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 995
    • LBP DI Box
Re: Switched Neutral
« Reply #3 on: June 11, 2014, 02:10:27 pm »

Frank - How did you find the switched neutral? Did you measure first or were you "surprised"?  I've found them both ways, I'm sorry to say.

I didn't take a meter up with me  (as it is, the trap doors are so small I can not put things in my pockets, and I need both hands to climb the vertical ladders so I put a few tools in a cloth bag at the end of a rope.  I knew the power was off and checked that the lights didn't work, but even when I KNOW the power is off I use a old habit I developed when I was a field service tech. 
1   Make sure the power is off
2.  Before doing anything else use a screwdriver to short the screw over the power wire to the box ground.
3.  Examine the big black spot on the screwdriver.

Repeat

When I was a field service tech the local maintenance guy would sometimes take offense. I would show him the screw driver with the scars from previous customer sites.

Usually it was the wrong breaker, not a switched neutral.
Logged
Not to Code

Jeff Bankston

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2268
Re: Switched Neutral
« Reply #4 on: June 16, 2014, 06:11:22 am »

i'v encountered that a number of times. i was helping my landlord install a celling fan in his house and the guy that wired it had the neutral on the switch. that can be a shocking experience.
Logged

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2228
Re: Switched Neutral
« Reply #5 on: June 16, 2014, 07:55:36 am »

Here is a fuse "box" I came across this week while estimating some electrical repairs.  A breaker panel had already been installed in tis home-I was very surprised to see this when I opened an unmarked wooden panel  I thought it was just an access panel.  Feeder comes in lower left through DP knife switch.  This a 120 V circuit-one main and 4 branch circuits, but fuses in every wire-obviously including the neutral.

Not poor workmanship-this was "state of the art" when it was installed!
Logged
Steve Swaffer

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3355
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Switched Neutral
« Reply #6 on: June 16, 2014, 03:08:47 pm »

Here is a fuse "box" I came across this week while estimating some electrical repairs.  A breaker panel had already been installed in tis home-I was very surprised to see this when I opened an unmarked wooden panel  I thought it was just an access panel.  Feeder comes in lower left through DP knife switch.  This a 120 V circuit-one main and 4 branch circuits, but fuses in every wire-obviously including the neutral.

Not poor workmanship-this was "state of the art" when it was installed!

It's a beauty, and totally terrifying by today's standards. One of the theaters in my town had exposed knife switches and fused hot/neutral wires feeding the theatrical lighting up until about 30 years ago. So the lighting operator stood in front of an bunch of hot knife switches with exposed, live bus bars everywhere. I remember when OSHA made them put a chicken-wire wall behind the lighting panel so a performer running by didn't push the lighting guy into the mass of hot/exposed wiring. That would have left a mark.

Good times...  8)
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Jeff Bankston

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2268
Re: Switched Neutral
« Reply #7 on: June 16, 2014, 10:00:51 pm »

Here is a fuse "box" I came across this week while estimating some electrical repairs.  A breaker panel had already been installed in tis home-I was very surprised to see this when I opened an unmarked wooden panel  I thought it was just an access panel.  Feeder comes in lower left through DP knife switch.  This a 120 V circuit-one main and 4 branch circuits, but fuses in every wire-obviously including the neutral.

Not poor workmanship-this was "state of the art" when it was installed!
EEEEEEEEK ! RUN AWAY RUN AWAY ! BAD BUNNY RABBIT !
Logged

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2228
Re: Switched Neutral
« Reply #8 on: June 17, 2014, 11:35:07 am »

I remember when OSHA made them put a chicken-wire wall behind the lighting panel so a performer running by didn't push the lighting guy into the mass of hot/exposed wiring.

Maybe I am not hearing/picturing this correctly?  But if I am standing in front of a mass of hot/exposed wiring, the last thing I want "protecting" me is a presumably grounded metal fence!?!
Logged
Steve Swaffer

Jonathan Johnson

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2997
  • Southwest Washington (state, not DC)
Re: Switched Neutral
« Reply #9 on: June 17, 2014, 11:37:10 am »

This a 120 V circuit-one main and 4 branch circuits, but fuses in every wire-obviously including the neutral.

Not poor workmanship-this was "state of the art" when it was installed!

The picture isn't clear enough to tell for sure, but I would not be surprised if those are 30A time-delay fuses "protecting" 14 AWG wire.

I really like the plaster "box".
Logged
Stop confusing the issue with facts and logic!

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3355
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Switched Neutral
« Reply #10 on: June 17, 2014, 07:44:19 pm »

Maybe I am not hearing/picturing this correctly?  But if I am standing in front of a mass of hot/exposed wiring, the last thing I want "protecting" me is a presumably grounded metal fence!?!
Yes, you ARE picturing it correctly. A grounded chicken wire fence right behind your back and exposed live copper bus bars in front of you. Of course, this is all gone now, but it was pretty terrifying when I saw it the first time.   
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Cailen Waddell

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1428
Re: Switched Neutral
« Reply #11 on: June 17, 2014, 08:05:24 pm »


Yes, you ARE picturing it correctly. A grounded chicken wire fence right behind your back and exposed live copper bus bars in front of you. Of course, this is all gone now, but it was pretty terrifying when I saw it the first time.

So being a lighting guy at heart (the secret is out),  I wonder if/how many arc flash accidents occurred with old resistance dimmer boards....


Sent from my iPhone using Tapatalk
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 20415
  • Wichita, Kansas USA
Re: Switched Neutral
« Reply #12 on: June 17, 2014, 11:31:05 pm »

Yes, you ARE picturing it correctly. A grounded chicken wire fence right behind your back and exposed live copper bus bars in front of you. Of course, this is all gone now, but it was pretty terrifying when I saw it the first time.

You know you're surrounded by nitwits when you see something like that and say "OMFG...." and the guy next to you asks "what's wrong?"
Logged
"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3355
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Switched Neutral
« Reply #13 on: June 18, 2014, 08:57:30 am »

You know you're surrounded by nitwits when you see something like that and say "OMFG...." and the guy next to you asks "what's wrong?"

Yeah, and there was a wooden step-stool in front of the open bus-bars so the shorter operators could reach the knife switches near the top of the panel. Like it said... terrifying.

Of course, historically theaters used to use wooden tubs full of brine (salt water) with perforated metal plates inside that could be moved up and down using a broomstick to dim the electric lights. Switched neutrals seems relatively safe by those standards.
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2228
Re: Switched Neutral
« Reply #14 on: June 18, 2014, 12:42:41 pm »

My dad worked on the lighting crew for theater at Bob Jones University back in the late 50's early 60's.  He has told me stories working with the open rheostats-and how they would sometimes stick especially during rapid transitions-leaving the operator the object of the directors frustration.

I am amazed at how may people open panels, etc without paying attention to their surroundings-clearances/people in the area.  Especially with live audio/lighting I would think others being around could be a major concern.  Part of the arc flash standard is setting up barriers for when you are in a live panel.  Maybe not as practical for a quick hookup, but having somebody in the area that may not be paying attention has always made me nervous.
Logged
Steve Swaffer

Jeff Bankston

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2268
Re: Switched Neutral
« Reply #15 on: June 18, 2014, 04:27:59 pm »

My dad worked on the lighting crew for theater at Bob Jones University back in the late 50's early 60's.  He has told me stories working with the open rheostats-and how they would sometimes stick especially during rapid transitions-leaving the operator the object of the directors frustration.

I am amazed at how may people open panels, etc without paying attention to their surroundings-clearances/people in the area.  Especially with live audio/lighting I would think others being around could be a major concern.  Part of the arc flash standard is setting up barriers for when you are in a live panel.  Maybe not as practical for a quick hookup, but having somebody in the area that may not be paying attention has always made me nervous.
i am always very careful when opening panels and switch gear. guys have gotten injured and killed from covers contacting lugs and buss bars. some of the designs dont allow much clearance between stuff. even breaker panels with dead fronts need to be handle carefully. but my biggest nightmare has ben older swirch gear thats got loose screws holding it together and ready to fall apart. always open doors to switch very slowly. theres a youtube video of a guy that opened doors to quickly and stired up dust with moisture and he got lit up. a security camera recorded it.
Logged

Steve M Smith

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3202
  • Isle of Wight - England
Re: Switched Neutral
« Reply #16 on: June 18, 2014, 05:44:00 pm »

Yes, you ARE picturing it correctly. A grounded chicken wire fence right behind your back and exposed live copper bus bars in front of you.

Someone actually bothered to ground it?


Steve.
Logged

Lyle Williams

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1556
Re: Switched Neutral
« Reply #17 on: June 19, 2014, 05:33:32 am »

Someone actually bothered to ground it?


Steve.

Maybe they knew what they were doing.  Mr McCoy making things nice and safe at the Hatfield Theatre.  :-)

Logged

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3355
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Switched Neutral
« Reply #18 on: June 19, 2014, 06:55:12 am »

Maybe they knew what they were doing.  Mr McCoy making things nice and safe at the Hatfield Theatre.  :-)

Well, I can't be sure it was grounded, so who knows. But I'm sure the exposed copper bus bars were hot.  ::)

I was a young engineering pup in my 20's doing sound for a rock band at this theater, so I didn't touch the lighting (lucky for me). I just remember seeing this crazy rig and asking about this new fence. They said it was obviously so that nobody pushed the lighting operator into the open circuits. I've got to wonder if there was an incident that made them build the chicken wire wall? Also, this was in the early 70's around the time I was getting OSHA certified at my day job, and OSHA was a baby industry at the time starting in 1970 IIRC. So all the power they had at the time was to recommend a chicken wire fence around the deadly lighting controller. Boy how things have changed...
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Jonathan Johnson

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2997
  • Southwest Washington (state, not DC)
Re: Switched Neutral
« Reply #19 on: June 19, 2014, 12:17:49 pm »

I've got to wonder if there was an incident that made them build the chicken wire wall?

Fried chicken. Mmmmm.
Logged
Stop confusing the issue with facts and logic!

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3355
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Switched Neutral
« Reply #20 on: June 19, 2014, 04:37:54 pm »

Fried chicken. Mmmmm.

Now I'm getting hungry.  8)
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

ProSoundWeb Community

Re: Switched Neutral
« Reply #20 on: June 19, 2014, 04:37:54 pm »


Pages: 1 2 3 [All]   Go Up
 



Page created in 0.093 seconds with 24 queries.