Would the US electrical code allow this ?

This is the place for any magazine-related discussions that don't fit in any of the column discussion boards below.
Post Reply
User avatar
Externet
Posts: 1800
Joined: Fri Feb 01, 2002 1:01 am
Location: Mideast USA
Contact:

Would the US electrical code allow this ?

Post by Externet » Mon Nov 26, 2012 6:10 pm

Hi fellows.
The purpose is to have together with a plain incandescent 120VAC light bulb on the ceiling; a couple of 'little' LEDs on when the incandescent is off.

-Switching the neutral and using the ground conductor for a tiny current

Code: Select all

Phase---------------------------------------------------------------------------------------------------------------
                                                                         LAMP
Neutral-------------------wall switch-------------------------------------                                       LEDs

Ground-------------------------------------------------------------------------------------------------------------
- The leds driven direct from mains capacitively.
- On a dark room, there is always a faint light.
- If the incandescent is in a metal enclosure, will use the grounding too.
- Abolish the deciBel ! -

Robert Reed
Posts: 2276
Joined: Wed Nov 24, 2004 1:01 am
Location: ASHTABULA,OHIO
Contact:

Re: Would the US electrical code allow this ?

Post by Robert Reed » Mon Nov 26, 2012 6:51 pm

How can you be sure the neutral will have enough voltage on it to drive a pair of LEDs? In an ideal world there is NO potential here. In my real world I have seen varying voltages present of almost zero to 2 vac. Always the neutral voltage is a function of load current in the TOTAL paths back to the service entry point and varys with time and usage.

dyarker
Posts: 1664
Joined: Fri Aug 22, 2003 1:01 am
Location: (somewhere), Afghanistan; from Rochester, NY
Contact:

Re: Would the US electrical code allow this ?

Post by dyarker » Tue Nov 27, 2012 7:22 am

Never, ever, switch the neutral.
And why worry about the LEDs being off when lamp is on?

Cheers,
Dale Y

gerty
Posts: 290
Joined: Mon Dec 06, 2004 1:01 am
Location: Tennessee
Contact:

Re: Would the US electrical code allow this ?

Post by gerty » Tue Nov 27, 2012 7:31 am

As already stated, you don't switch neutral, and you don't use the ground as a current carrying conductor.
If you had another conductor from switch box to light, you could change switch out for a 3 way, one position = light the other position = led. But I guess you already knew that :grin:

User avatar
Externet
Posts: 1800
Joined: Fri Feb 01, 2002 1:01 am
Location: Mideast USA
Contact:

Re: Would the US electrical code allow this ?

Post by Externet » Tue Nov 27, 2012 8:39 am

Hi all.
Robert: The leds are not fed by the neutral wire on the (poor) schematic. The ground wire is. Even when both neutral and ground conductors are tied together at the breaker box. Waste of a conductor. Never got the full rationale of such.

Dale: Agree with phase being the one to be switched, for safety. But seen many old house installations where by routing convenience of the then electrician, the neutral was switched for the light fixture. And by the schematic, leds are on all the time. Some older houses do not even have the ground wire.

gerty: Agreed. Having another conductor available for the leds would be feasible on new construction only, could not be implemented on an existing wiring. And those 3 way $witches could be implemented by still having to add an additional wire on an old construction, not a simple task.

The thing is to implement the leds with minimum of alterations... Well, I will not tell the inspector... :grin:

================================================================================

PART TWO:
Some wall switches have a neon lamp in parallel to the switch, it is a nice feature to locate the switch in a dark room.

Now, that poses a shock risk by presence of phase at the ceiling bulb socket when switch is off, and it is an approved device. (or is it not in US ?)
If yes, a pair of (white) leds could be implemented same parallel way at the wall switch cover to both locate the switch in darkness and providing faint illumination to the room when the incandescent is off.

Any different electrical code attitude towards a few milliamperes by led implementation and a fraction of a milliampere as with neon ?

Edited - added ---> idiot priced lighted switch ---> http://www.ebay.com/itm/HUBBELL-HBL1221 ... 0810282615
Found someone already markets my plan : http://www.prweb.com/releases/2005/12/prweb319601.htm

Miguel
- Abolish the deciBel ! -

User avatar
Lenp
Posts: 1296
Joined: Thu Oct 26, 2006 8:11 pm
Location: Maryland
Contact:

Re: Would the US electrical code allow this ?

Post by Lenp » Tue Nov 27, 2012 12:40 pm

Externet wrote: Even when both neutral and ground conductors are tied together at the breaker box. Waste of a conductor. Never got the full rationale of such.
By definition: "A neutral is an intentional current carrying conductor"
It is designed to carry any current that results from an imbalance on the power phases.
In the perfect world, the imbalance is zero in a multi-phase system. If you had 2 matched incandescent lamps, wired across the 120/240 service, lamp#1 from phase A to neutral and lamp#2 from phase B to neutral, there would be zero neutral current. Disconnect the neutral, nothing happens! In a single phase system, like 120V, the neutral MUST carry the same current as being supplied by the power phase. There is nowhere else for it to go except if there is a defect and the current finds another path, like through you! So, if there is current, there is voltage. How much is determined by the resistance of the conductor.

By definition: "A ground is an unintentional current carrying conductor"
The ground should never carry current as a normal connection. It is designed to carry fault, not imbalance current.
Yes, the neutral and ground are bonded at the point of origin, but should never be bonded together elsewhere in the system. In fact there are isolated ground systems that use an insulated grounding conductor that connects only to the grounding screw of special devices that have their grounding screw isolated from the device mounting yoke. You have Power, Neutral, Iso Ground and equipment ground. If the ground were to carry intentional current, many problems can result. If the ground becomes disconnected, all the grounding circuit towards the disconnect can become energized. The ground is also bonded to building steel, water lines and other grounded structures for redundancy and to improve the conduction to earth. If current took these paths electrolysis would occur and damage would be done.

Ac power wiring IS NOT at all like automobile wiring, with one wire and a chassis ground.

The subject of grounding and neutrals becomes way more complex when distribution transformers are used on poly phase systems.

Len
Len

“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)

desy2820
Posts: 24
Joined: Sat Aug 25, 2007 7:54 pm
Contact:

Re: Would the US electrical code allow this ?

Post by desy2820 » Sat Dec 01, 2012 8:08 am

No, code will not allow this.

Depending on how much light you need, would a lighted switch work for you? I've seen both the old-school lighted toggles and new "decora" style lighted. The only sticky part is that the switch box itself (in the wall) must have a neutral for the "light" part of the switch to work, not all of them are wired this way.
Note: This link is an example, not an endorsement!

Something like this: http://www.homedepot.com/Electrical/h_d ... reId=10051

Although it may be well within your capabilities, I wouldn't recommend rolling your own. Stick with something UL (or equivalent) rated.

Another idea, not nearly as pretty or elegant, would be to whip something up based on a photocell or photodiode, transitors, and some LEDs. This would be powered by a wall-wart (low voltage), then you can just run two low voltage power wires where you want the light placed. If you're feeling really ambitous, it could be battery-backed, and come on if the power went out too!

User avatar
MrAl
Posts: 3856
Joined: Fri Jan 11, 2002 1:01 am
Location: NewJersey
Contact:

Re: Would the US electrical code allow this ?

Post by MrAl » Thu Dec 06, 2012 2:15 am

Hi,

I see you are talking about jumping the switch with a very low current lighting device, like the LED. So you would maybe run 5ma through the LED even when the lamp switch is turned off, and 5ma would also run though the light itself. You apparently want the switch to light up when it is off.

If that's all you want, buy a lit up switch. They sell them at Home Depot. Can spot them easy in the dark.

If you want a little "extra light" like as if it was to double as a night light, you might be able to install a double box and make one side a receptacle and then plug in a LED night light that turns off when it senses light. This setup would definitely be a worthy project and would pass any inspection i would think because light switches and receptacles always pass unless something is wrong with them of course.

You might also find a receptacle and switch built into one unit, where the whole thing takes a regular receptacle face plate and so the actual receptacle shows up as only one receptacle (normally there is two in one box) and the light switch shows up in the other hole of the face plate. You could then plug the LED night light into the receptacle and would not need a lighted switch because the night light would be on when it was off. This would fit into an existing single wall box.
LEDs vs Bulbs, LEDs are winning.

jimmy101
Posts: 82
Joined: Tue Mar 24, 2009 11:08 am
Contact:

Re: Would the US electrical code allow this ?

Post by jimmy101 » Tue Dec 25, 2012 9:57 am

If you want more light than what a typical lighted switch provides you can just use a standard wall mounted "three-way" (Single-Pole, Double-Throw SPDT) switch. Three-way switches are typically used to control a circuit (like lights) from more than one location. Here though you are controlling two lights from one location. One leg of the switch goes to the regular room lights and the other to the LED light(s). When one circuit is on the other is off. AFAIK that is code compliant.

User avatar
haklesup
Posts: 2848
Joined: Thu Aug 01, 2002 1:01 am
Location: San Jose CA
Contact:

Re: Would the US electrical code allow this ?

Post by haklesup » Wed Jan 02, 2013 12:58 pm

I've done this with a neon lamp, I suppose you can do it with LED and a CAP (particularly if it is enclosed in a J box). All you need to do is place the lamp across the switch terminals (Hot and switched hot, Black and Red if you prefer) with the rest of the circuit wired in the conventional way. When the switch is open it will light as long as there is an unblown incandescent bulb or some CFL lamps or most transformer based fluorsecents (there has to be a path back to neutral that includes the luminary load). When the switch is open there will be a voltage drop across the switch allowing the indicator lamp to light while the luminary is off. When the switch is closed, the indicator lamp will be shorted out and have 0V across it (unlit) while the luminary is lit.

Post Reply

Who is online

Users browsing this forum: dacflyer, Google [Bot] and 8 guests