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Author Topic: Tell me I'm not losing my mind  (Read 2198 times)

David Allred

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Tell me I'm not losing my mind
« on: June 04, 2019, 10:36:37 am »

For an exterior building light project I handle the communications for the venue with the electrician of what I needed.
Yada-yada I need 120vac to these 9 locations.  7 on the ground and 2 on the roof. 
I need the an exterior kill switch (for maint) on the hot leg serving all locations.
I need a switch leg inside to the office space for a USB timer relay board, that runs off a PC's clock and powered thru the USB connection.  I want the switch on the neutral leg.
(1st sign of trouble - he refers to the relay as a transformer.  I refer to it again as "a simple switch that just needs a loop out to the exterior junction box" because at the time there was talk of tying into an exist circuit already run outside.  He continued... "you need power run to the transformer, right?"   I correct him again, saying "No", it is 100% powered from the PC's USB cable, no power run needed, just a switch leg.)

Electrical work is completed.  I pop the ceiling panels to connect the USB relay  to the switch leg and there are 2 wire sets.  One marked "Hot" and one marked "switch leg).
I called him up and asked what I was supposed to do with this?  Was the Hot run just a spare in case I wanted a power source.  His reply, "That's for the transformer."   I explain again....... so he says he will make it right, but will have to run another wire to get power outside.

I examined the outside junction box.  The "switch leg" is wired black - black, white - white, & ground - ground with all 3 branches going to the 9 locations.  He really (apparently) thought is was a transformer.

Attach is the "as-wired" and my proposal to him to resolve the problem without running an additional hot wire out side.
His reply, "No that will not work sir. You will not have neutral outside. And you don't have a actual switch leg coming back. You have the neutral wire returning. If outside switch was only switch then it would work but not coming back to your relay."
I added the red note and replied, "See the note in red.  There is a neutral.  It feeds through the inside switch."
He replies, "Still got to have another wire going out. It's not a problem, I can fix tomorrow."
My reply, "Don't need another wire, we can use the one switch leg for power and switch."
His reply, "Ok then which one is your return switch leg?"
I reply, "The inside switch (timer relay) is breaking into the neutral wire of the power feed going outside.  It will kill power going to the junction box."

I know I'm right, but he's the professional.  Am I losing my mind?

Thanks





« Last Edit: June 04, 2019, 10:40:35 am by David Allred »
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John Roberts {JR}

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Re: Tell me I'm not losing my mind
« Reply #1 on: June 04, 2019, 10:57:17 am »

I had a similar question until I went back and reread your post. Your schematic is not obvious that the timer switch is externally powered (via USB). Your current version section seems unfinished or incorrect, but presumably that is working.

It is probably not good practice (code?) to break the neutral instead of line. This leaves the hot leg energized even when neutral is open. 

JR
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David Allred

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Re: Tell me I'm not losing my mind
« Reply #2 on: June 04, 2019, 11:22:46 am »

I had a similar question until I went back and reread your post. Your schematic is not obvious that the timer switch is externally powered (via USB). Your current version section seems unfinished or incorrect, but presumably that is working.

It is probably not good practice (code?) to break the neutral instead of line. This leaves the hot leg energized even when neutral is open. 

JR
The illustration was made after the wiring was complete to show him how I thought it could be made to work.  The "Current" definitely does NOT work, as the hot leg from the breaker box is not connected to anything.
You raise a similar concern as the electrician about breaking the neutral.  He said the light might not work right.   I will change the relay to the hot leg.
« Last Edit: June 04, 2019, 11:33:13 am by David Allred »
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David Allred

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Re: Tell me I'm not losing my mind
« Reply #3 on: June 04, 2019, 11:41:51 am »

When I was a teenager doing construction work the general contractor taught me to wire switches on the neutral.  His logic (that still seems logical) was that IF the circuit was still live and you grabbed the neutral wire in the switch box and touched the grounded box you wouldn't get shocked.  I have held that principle for 30+ years.  On a given circuit there would be fewer shock hazards.
I learned something new today.
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Tim McCulloch

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Re: Tell me I'm not losing my mind
« Reply #4 on: June 04, 2019, 12:01:01 pm »

When I was a teenager doing construction work the general contractor taught me to wire switches on the neutral.  His logic (that still seems logical) was that IF the circuit was still live and you grabbed the neutral wire in the switch box and touched the grounded box you wouldn't get shocked.  I have held that principle for 30+ years.  On a given circuit there would be fewer shock hazards.
I learned something new today.

It's a Code violation to open the neutral without simultaneously opening the line.  With a single pole switch the LINE, and only the line, is to be switched.
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Chris Hindle

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Re: Tell me I'm not losing my mind
« Reply #5 on: June 04, 2019, 12:30:29 pm »

When I was a teenager doing construction work the general contractor taught me to wire switches on the neutral.  His logic (that still seems logical) was that IF the circuit was still live and you grabbed the neutral wire in the switch box and touched the grounded box you wouldn't get shocked.  I have held that principle for 30+ years.  On a given circuit there would be fewer shock hazards.
I learned something new today.
Wow.
Just wow.
With the line live throughout the "network", how is there less shock risk?
Pretty spectacular shock risk just changing a light bulb...
Ever have one where the bulb breaks off, and you go in with needle-nose to clear the socket?
My dad taught me to keep one hand in my pocket when digging around a panel. That's saved my ass a few times....
Chris.
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Stephen Swaffer

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Re: Tell me I'm not losing my mind
« Reply #6 on: June 04, 2019, 12:55:30 pm »

When I was a teenager doing construction work the general contractor taught me to wire switches on the neutral.  His logic (that still seems logical) was that IF the circuit was still live and you grabbed the neutral wire in the switch box and touched the grounded box you wouldn't get shocked.  I have held that principle for 30+ years.  On a given circuit there would be fewer shock hazards.

Until someone turns a light "off" and proceeds to replace the fixture??

Tim is right-specific reference is 404.2.  Following standard practice will result in less confusion.  Unfortunately, a signficant number of electricians don't understand how to make a circuit work they just know to connect the hot wire to the brass colored screw and so on....and please don't confuse them by asking them to explain a 3 way switch!

Neutral switching used to be common practice-you'll still run into in older homes quite frequently.
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David Allred

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Re: Tell me I'm not losing my mind
« Reply #7 on: June 04, 2019, 04:21:31 pm »

Wow.
Just wow.
With the line live throughout the "network", how is there less shock risk?
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. 
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Mike Sokol

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Re: Tell me I'm not losing my mind
« Reply #8 on: June 04, 2019, 04:50:14 pm »

It's a Code violation to open the neutral without simultaneously opening the line.  With a single pole switch the LINE, and only the line, is to be switched.

Opening just the neutral, either through a switch or a fuse, is a very bad idea. I remember snooping around the Maryland Theater back in the 70's when they still had their original 1920's wiring in place, and every single stage lighting fixture had two fuses. One fuse on the hot and one fuse on the neutral. The electrician I was working with at the time told me the original designers wanted to protect the neutral wires until everyone figured out how dangerous backfeeding the voltage/current through the tungsten bulb would be.                                                                                                     
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brian maddox

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Re: Tell me I'm not losing my mind
« Reply #9 on: June 04, 2019, 10:14:06 pm »


Neutral switching used to be common practice-you'll still run into in older homes quite frequently.

Yup.  Found out my house has a few of those the hard way.  Got bit because i just turned the switch off rather than killing the breaker before digging into something [i forget what exactly].  I had never even HEARD of neutral switching before....
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Stephen Swaffer

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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.
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Steve Swaffer

David Allred

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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).   :)
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Stephen Swaffer

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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.
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Steve Swaffer

Keith Broughton

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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.
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David Allred

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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 »
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John Roberts {JR}

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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

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Chris Hindle

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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.
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TJ (Tom) Cornish

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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 »
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Stephen Swaffer

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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.
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Steve Swaffer

TJ (Tom) Cornish

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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.
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David Allred

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Re: Tell me I'm not losing my mind
« Reply #20 on: June 06, 2019, 02:51:59 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...
JR

I thought that is what the diagram showed (voltage flowing through a device (bulb filament) and up the neutral leg).

It seems like the code was written for working on a live circuit... or rather written in case someone willfully or ignorantly works on a live circuit.
Isn't it moot if the circuit is off, confirmed off (metered), and locked out properly.  (again, not arguing for using the neutral for switching)
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TJ (Tom) Cornish

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Re: Tell me I'm not losing my mind
« Reply #21 on: June 06, 2019, 03:52:38 pm »

I thought that is what the diagram showed (voltage flowing through a device (bulb filament) and up the neutral leg).

It seems like the code was written for working on a live circuit... or rather written in case someone willfully or ignorantly works on a live circuit.
Isn't it moot if the circuit is off, confirmed off (metered), and locked out properly.  (again, not arguing for using the neutral for switching)
The code is (IMO) logical.  Switching on the hot leg turns off the supply of voltage/shock hazard at the switch, just like turning off your garden hose valve stops the flow of water downstream of the switch.

Your contractor friend had a misunderstanding of current flow. The original message you posted was
Quote
...was that IF the circuit was still live and you grabbed the neutral wire in the switch box and touched the grounded box you wouldn't get shocked.
If you grabbed the neutral wire in a box properly switched on the hot wire, you can touch the box without issue as it is bonded at the panel - no voltage potential difference. Contrary to your friend's belief, if you switched on the neutral and were touching something downstream of the switch, you WOULD be shocked if you touched between neutral and ground, as now neutral is floating up to line voltage through the energized load.
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Re: Tell me I'm not losing my mind
« Reply #21 on: June 06, 2019, 03:52:38 pm »


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