Shared Neutrals in dimming circuits

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edelec40

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Is there NEC code for residential lighting control pertaining to shared neutrals in Dimming lighting control circuits? If so where. With dimming circuits feeding voltage back on neutral and harmonics on nuetral is shared nuetrals not a fire hazard?
 
Re: Shared Neutrals in dimming circuits

Harmonics are not an issue for the neutral with a 240/120 single phase supply system.
 
Re: Shared Neutrals in dimming circuits

However, a shared branch circuit neutral will void the warranty of any dimmer that is on the market. A shared feeder or service neutral is not a problem.

In quite a few situations with electronic equipment, the manufacturer's requirements overrule NEC. For instance, this past summer we hooked up a CAT scanner with a nameplate rating of 120 amps full load current. We had to use 4/0 copper hot wires, 4/0 copper equipment ground, and a 4/0 redundant grounding electrode conductor from the local disconnect to the building steel!
 
Re: Shared Neutrals in dimming circuits

Originally posted by mc5w:
However, a shared branch circuit neutral will void the warranty of any dimmer that is on the market. A shared feeder or service neutral is not a problem.
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Do you have any references for that?
 
Re: Shared Neutrals in dimming circuits

Go over to Lutron's website and download their installation and technical instructions for all their different dimmers, which will take a lot of time even with DSL. Or, just call them up.

Do the same with every other manufacturer.
 
Re: Shared Neutrals in dimming circuits

A dedicated neutral would be kind of pointless when the hot is shared with outher outlets. So what you're really gonna need is a dedicated circuit if you're going to use a dimmer.
 
Re: Shared Neutrals in dimming circuits

Originally posted by mc5w:
Go over to Lutron's website and download their installation and technical instructions for all their different dimmers, which will take a lot of time even with DSL. Or, just call them up.

Do the same with every other manufacturer.
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mc5w first as has already been said...Welcome to Mike Holt's Forum.

I have been reading your posts and it is obvious you have much to offer. :)

Just for the record I went to Pass and Seymour's site and could find nothing to back up your thoughts.

Again, welcome, hope you stick around, Bob

[ March 21, 2005, 05:00 AM: Message edited by: iwire ]
 
Re: Shared Neutrals in dimming circuits

Yeah, mc, welcome to the forum. You've had a busy night! :D

I'd kinda question the analogy of a dimmer to a 120 amp CAT scanner. :D

I too am curious to see what you can dig up on this. Never heard of wiring restrictions from dimmer instructions, aside from things that would cause the dimmer not to function out of the box.
 
Re: Shared Neutrals in dimming circuits

The problem that dimmer manufacturers have with share neutral branch circuits is that in a branch circuit the neutral connections are not as secure as in a feeder or service. That said, if a wirenut(R) or scotchlok(R) comes undone the dimmer could be exposed to more than 125 volts.
 
Re: Shared Neutrals in dimming circuits

Hi mc.

Any equipment connected to a multiwire branch circuit is subject to damage from a lost neutral.

That could be a lighting fixture, a toaster, a home entertainment system or a dimmer.

Now will any manufacture warranty an item that has been subject to over voltage? I doubt it and I don't blame them. :)

I still would not hesitate to feed a dimmer with a MWBC. :cool:

Bob
 
Re: Shared Neutrals in dimming circuits

Originally posted by mc5w:
That said, if a wirenut(R) or scotchlok(R) comes undone the dimmer could be exposed to more than 125 volts.
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I always enjoy a good multiwire circuit debate. Let the games begin!!
 
Re: Shared Neutrals in dimming circuits

Alright, you asked for it Peter.

I think multiwire circuits are harmful because the more conductive material we put above the earth's surface the higher we raise the mean altitude of the bottom side of the ionosphere. In turn raising it's outer altitude. The further the ionosphere extends the more protection from ultraviolet and cosmic radiation it provides.

That's the real reason multiwire circuits are irresponsible.
 
Re: Shared Neutrals in dimming circuits

Wow Sam, you're right. That never occured to me. :)

I'm never using multiwire circuits again. I hope others will follow suit.
 
Re: Shared Neutrals in dimming circuits

Originally posted by mc5w:
That said, if a wirenut(R) or scotchlok(R) comes undone the dimmer could be exposed to more than 125 volts.
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And exactly when and why would these wire nuts come undone?

We don't use the "DIYer" scenario or the "helper didn't make the joint correctly" arguments. :D

Roger
 
Re: Shared Neutrals in dimming circuits

Originally posted by physis:
the more conductive material we put above the earth's surface the higher we raise the mean altitude of the bottom side of the ionosphere. In turn raising it's outer altitude. The further the ionosphere extends the more protection from ultraviolet and cosmic radiation it provides.
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Sam you are like, totally from California aren't you? :D
 
Re: Shared Neutrals in dimming circuits

Well, at least I didn't go to Berkeley.

Edit: Like, totally, :D I'm not from the valley. Although I spent a year down there.

[ March 21, 2005, 04:14 PM: Message edited by: physis ]
 
Re: Shared Neutrals in dimming circuits

Originally posted by roger:

Sam and Peter, that is not a legitimate argument either.
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Well Roger, we must always stay on the side of caution. While evidence is sketchy, the ionization effect can't be ignored. No more MWBCs for me. In fact, I'm going to start wiring everything with ridgid, even doorbells, to provide maximum shielding from this harmful effect.
 
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