404.2(C)(5)- 2014

[kwired]

The reason for a neutral in every switch box is for safety. As I remember it's meant to prevent end users from replacing a standard switch with a device that requires a neutral. What ends up happening is they tie the neutral to the ground because they don't know any better. That's a no - no.

Any untraine person can do worse then that because they don't know any better. NEC is not supposed to be about protecting the non qualified if they are attempting electrical work.

The only reason I can see a N wire at the switch is for the cable industry to sell us cable with more wires in it to make more money.

If there is a component that places current on a grounded conductor there is good reason to use a grounded conductor and not an equipment grounding conductor.

Actually the problem is the sensor device may be listed as using the EGC as a noodle. The rule was made so UL would quit listing these devices.

That right there is the biggest issue here, NFPA vs UL, and we get stuck with whatever compromise was made.

 

[Fitzdrew516]

Any untraine person can do worse then that because they don't know any better. NEC is not supposed to be about protecting the non qualified if they are attempting electrical work.

I get that and I agree with you, but there has to be some reasonable expectation set as well. How many people do you think hire an electrician to change out a switch?

 

[Sierrasparky]

The neutral was required for all the reasons already stated and also as probably an additional not well known good , it helps to eliminate EMF issues.

If one wires from the source to the switch or switches and then to the switch leg to the light no issue and a neutral winds up in each box.

When you use the source at both ends or the one 3 way is just a end run, Both hot neutral current does not make the exact same path from source to light.

When you do this you have a potential for NET currents and or greater EMF.

 

[kwired]

I get that and I agree with you, but there has to be some reasonable expectation set as well. How many people do you think hire an electrician to change out a switch?

And if they run into difficulty they should contact a qualified person. I don't know how many times I run into situation where a three way switch was attempted to be replaced with a single pole switch with one of the ungrounded conductor leads landed on the device EGC terminal because there were no other terminals to land it on.

If the occupancy sensor or other device has a neutral terminal and they don't have a conductor present to land there - they will either leave it unused and the device likely doesn't work, or if they are a little smarter may connect it to the EGC, but they introduced any hazard not a qualified person. Sort of similar situation as if same person installs a bootleg EGC from the grounded conductor on some old wiring.

Has been said before that you can't idiot proof everything. If you do accomplish that task an improved idiot will eventually come around.

 

[kenaslan]

The neutral was required for all the reasons already stated and also as probably an additional not well known good , it helps to eliminate EMF issues.

If one wires from the source to the switch or switches and then to the switch leg to the light no issue and a neutral winds up in each box.

When you use the source at both ends or the one 3 way is just a end run, Both hot neutral current does not make the exact same path from source to light.

When you do this you have a potential for NET currents and or greater EMF.

If the 3-Way is at one end, one of the travelers (switch leg) will be hot and return on the hot wire. So current is flowing BOTH directions at the same time, in the cable, and it is balanced.

 

[mwm1752]

Can anyone make sense as to why this rule is as written. Looks like if there is a 3 way in a room and both switches are in the room then no neutral is needed. Here is the actual text which is basically an exception

Actually, no nuetral is required, the need for the grounded conductor is a choice for the installer to make. Perfect example of code is minimum.

 

[K8MHZ]

Actually, no nuetral is required, the need for the grounded conductor is a choice for the installer to make. Perfect example of code is minimum.

After reading the proposal and it's acceptance, I think the graphic is incorrect.

I see that in a room with 3 way switches where the switches are in the room the light is in, a neutral is required, but only at one switch. That allows for a neutral in case an occ sensor would be used, as that is a likely scenario.

If a 3 way switch controls a light that is not in the same room (like an outside light), no neutral is required as it's not likely an occ sensor would be put in a switch box that isn't within sight of the light.

 

[Smart $]

...I see that in a room with 3 way switches where the switches are in the room the light is in, a neutral is required, but only at one switch. That allows for a neutral in case an occ sensor would be used, as that is a likely scenario.
...

IIRC, only if that switch can be viewed from any location within the illuminated space. I believe that is disregarding non-structural appurtenances.