ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3  All   Go Down

Author Topic: Tell me I'm not losing my mind  (Read 2200 times)

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2405
Re: Tell me I'm not losing my mind
« Reply #10 on: June 04, 2019, 10:21:35 pm »

2 rooms on a circuit.  4 plugs each and 1 switch each. 
Neutral switches - 8 shock points.
Hot switches - 10 shock points.
See? There is logic to that singular point.

That is only true if both switches are closed (on) and all wires connected.

Consider the current NEC term for a neutral-"grounded conductor".  As soon as you open the switch or disconnect one of the wires, the switch leg is no longer grounded.  In fact, if there is a light bulb in the socket or a ballast or any other load connected, it will now be hot with the current seeking a path somewhere to comlete the circuit.  The path may well me some unsuspecting "electrician".

If the switches are open/off there are still 10 shock points.
Logged
Steve Swaffer

David Allred

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1854
Re: Tell me I'm not losing my mind
« Reply #11 on: June 04, 2019, 11:35:18 pm »

That is only true if both switches are closed (on) and all wires connected.

Consider the current NEC term for a neutral-"grounded conductor".  As soon as you open the switch or disconnect one of the wires, the switch leg is no longer grounded.  In fact, if there is a light bulb in the socket or a ballast or any other load connected, it will now be hot with the current seeking a path somewhere to comlete the circuit.  The path may well me some unsuspecting "electrician".

If the switches are open/off there are still 10 shock points.

I was defining a shock point as wrapping your hand around the plug / switch and touching the screws.  No shock on the neutral switch (assuming no fault).   :)
Logged

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2405
Re: Tell me I'm not losing my mind
« Reply #12 on: June 05, 2019, 07:44:45 am »

My point is (I am NOT trying to be argumentative-I am trying to make sure we understand);  if that switch is "off" then the switch leg is just as hot as a hot wire on a receptacle because it will be energized through what ever load is there.  It will kill you just as dead that way as if you wrap your hand around a receptacle.  I don't consider a switch in the "off" position a fault-that is a normal condition.

There are multiple requirements in the NEC related to the dangers of disconnected "neutrals" because there have been far too many electrocutions from supposed "neutrals".  That switch does the same thing to that switch leg as removing a wire nut mid-circuit does to a neutral run.
Logged
Steve Swaffer

Keith Broughton

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3425
  • Toronto
Re: Tell me I'm not losing my mind
« Reply #13 on: June 05, 2019, 09:37:27 am »

I don't know about other places but here in Ontario, there is no switch or breaker on a neutral...ever!
As for fewer"shock points", I can't even begin to explain how faulty that argument is.
There will be NO shock points if , when working on wiring, the breaker is OFF for that cct.
Now, as for neutral passing through a switch box, the code has changed here recently to mandate neutrals be available in a switch box to allow for active "smart" switches and dimmers.
Logged
I don't care enough to be apathetic

David Allred

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1854
Re: Tell me I'm not losing my mind
« Reply #14 on: June 06, 2019, 11:42:24 am »

if that switch is "off" then the switch leg is just as hot as a hot wire on a receptacle because it will be energized through what ever load is there.  It will kill you just as dead that way as if you wrap your hand around a receptacle.  I don't consider a switch in the "off" position a fault-that is a normal condition.


I will repeat from my original post that I learned that switching the neutral is BAD.  I understand that.  I was just expressing why it made sense to do it that way (with limited knowledge).
I am just trying to understand why it is bad.  I think, from many comments here that the image below is the reason.
Does it show (explain) why?

David
« Last Edit: June 06, 2019, 11:44:53 am by David Allred »
Logged

John Roberts {JR}

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 16688
  • Hickory, Mississippi, USA
    • Resotune
Re: Tell me I'm not losing my mind
« Reply #15 on: June 06, 2019, 12:01:44 pm »

Pretty colors but still not sure you get it... The dominant problem from breaking neutral is that the now floating neutral wire, opened up by the switch, is energized by current conducting through the load from the still hot line attachment... This energized floating neutral is more than willing to flow into any return path it finds (like a grounded human). It will be current limited by the load, but still more than enough current to stop a human heart, or knock you off a ladder.

JR

Logged
When in doubt do what's right.

Chris Hindle

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 1995
  • Montreal, Quebec, Canada, Earth, Sol System,......
Re: Tell me I'm not losing my mind
« Reply #16 on: June 06, 2019, 12:24:22 pm »

2 rooms on a circuit.  4 plugs each and 1 switch each. 
Neutral switches - 8 shock points.
Hot switches - 10 shock points.
See? There is logic to that singular point.
ya, but everyone EXPECTS the hot to be live............
In your calculation, don't forget the light sockets.
Chris.
Logged
Ya, Whatever. Just throw a '57 on it, and get off my stage.

TJ (Tom) Cornish

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 4284
  • St. Paul, MN
Re: Tell me I'm not losing my mind
« Reply #17 on: June 06, 2019, 12:30:39 pm »

I will repeat from my original post that I learned that switching the neutral is BAD.  I understand that.  I was just expressing why it made sense to do it that way (with limited knowledge).
I am just trying to understand why it is bad.  I think, from many comments here that the image below is the reason.
Does it show (explain) why?

David
In your left diagram, the panel-side of the switch on the neutral wire will be near 0 volts no matter the switch position as the neutral wire is a near-zero impedance path back to ground. A heavily loaded circuit will cause the neutral -> ground voltage to climb due (counterintuitively) to voltage drop on the whole circuit. Only in your second diagram with the switch open does there become a shock hazard on the neutral wire as you now have a voltage difference between the two switch terminals.


The first rule of any electrical work is to never assume and to test everything and open neutrals happen inadvertently in real life - wire nut failures, etc., but switching is always done on the hot leg(s) because it removes voltage downstream of the switch, where switching on the neutral leg doesn’t.
« Last Edit: June 06, 2019, 02:48:10 pm by TJ (Tom) Cornish »
Logged

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2405
Re: Tell me I'm not losing my mind
« Reply #18 on: June 06, 2019, 01:29:24 pm »

In your left diagram, the panel-side of the switch on the neutral wire will be near 0 volts no matter the switch position as the neutral wire is a near-zero impedance path back to ground. A heavily loaded circuit will cause the neutral -> ground voltage to climb due (counterintuitively) to voltage drop on the whole circuit. Only in your second diagram with the switch closed does there become a shock hazard on the neutral wire as you now have a voltage difference between the two switch terminals.


The first rule of any electrical work is to never assume and to test everything and open neutrals happen inadvertently in real life - wire nut failures, etc., but switching is always done on the hot leg(s) because it removes voltage downstream of the switch, where switching on the neutral leg doesn’t.

I don't think you meant closed.

With the switch closed, the two terminals are connected with near zero resistance so there will be almost no (practically immeasurable) voltage difference.

If there is a good bulb in the socket in the right diagram, then with the switch open (lamp off) the left terminal will be "not hot" or at zero volts to ground and the right terminal will be "hot" or 120 volts to ground.  If the switch is closed (lamp on), then both terminals will be "not hot" or at zero volts (practically speaking).

As drawn with a burnt out lamp, the right terminal will always be "not hot" or at zero volts.
Logged
Steve Swaffer

TJ (Tom) Cornish

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 4284
  • St. Paul, MN
Re: Tell me I'm not losing my mind
« Reply #19 on: June 06, 2019, 02:48:46 pm »

I don't think you meant closed.

With the switch closed, the two terminals are connected with near zero resistance so there will be almost no (practically immeasurable) voltage difference.

If there is a good bulb in the socket in the right diagram, then with the switch open (lamp off) the left terminal will be "not hot" or at zero volts to ground and the right terminal will be "hot" or 120 volts to ground.  If the switch is closed (lamp on), then both terminals will be "not hot" or at zero volts (practically speaking).

As drawn with a burnt out lamp, the right terminal will always be "not hot" or at zero volts.
Thank you - that is what I meant. Post corrected.
Logged

ProSoundWeb Community

Re: Tell me I'm not losing my mind
« Reply #19 on: June 06, 2019, 02:48:46 pm »


Pages: 1 [2] 3  All   Go Up
 



Page created in 0.038 seconds with 23 queries.