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#78869 10/31/01 11:40 AM
Joined: Oct 2001
Posts: 597
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I've got a dimmer here that has instructions quoting '99 NEC 380-9(b)(2)exception.
Quote
Exception to (b): Where no grounding means exists within the snap-switch enclosure or where the wiring method does not include or provide an equipment ground, a snap switch without a grounding connection shall be permitted for replacement purposes only. A snap switch wired under the provisions of this exception and located within reach of conducting floors or other conducting surfaces shall be provided with a faceplate of nonconducting, noncombustible material.
I've got an ungrounded metal box, let's say, can I put the dimmer in, in place of the snap switch?

What confuses me is that the opening words of 380-9(b) says "Snap switches, including dimmer switches,. . ." and the exception uses snap switches only.

The dimmer manufacturer implies that I can install the dimmer in an ungrounded box without adding a ground.

Oww, my head hurts. :confused


Al Hildenbrand
2017 / 2014 NEC & Related Books and Study Guides
Joined: Mar 2001
Posts: 2,056
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IMO,
Because the rule states "snap switches, including dimmer switches..." I, personally would carry that inclusion over into the exception.

Joined: Oct 2001
Posts: 597
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Here's a little more of the hypothetical. My client is asking for a dimmer for the dining room light. The light's circuit is an original knob & tube (or 2 wire romex, no ground) with a 12 cu. in. metal switch box by the door to the kitchen. The switch box has 2 - #14 ga wires in it and is ungrounded. The dining room has a pored concrete floor on grade and a flat roof overhead. The client is trying to decide which dimmer to have installed. Of the list of dimmers she is considering, what is the correct choice?
<OL TYPE=A>

[*]Lutron Ariadni (snap switch with a slide dimmer)

[*]Push rotary with a knob that goes on after the faceplate

[*]Decora style touch sensitive electronic dimmer

[*]A slide dimmer with raised metal cooling fins

[*]An X10 dimmer switch controlled by a remote module

[*]Any one of the above

[*]None of the above

[*]Choose only from ____________ (fill in more than one, less than five)
</OL>


Al Hildenbrand
Joined: Mar 2001
Posts: 2,056
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A

Joined: Oct 2000
Posts: 5,389
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Al,
anyone but D, as it has some exposed conductables.

of interest, the 02' has the same wording for the Exception, now 404.9(B), with the right side change line, but i see no change.....it's worded the same
[Linked Image]

Joined: Oct 2001
Posts: 597
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Sparky,

I noticed the change line, too. Seems the description of what might be touched while also touching a faulty snap switch was verbally tweaked. In the last sentence of the Exception, "earth" was added for 2002 and "conducting floors" was changed to "grade conducting floors".

Around here, within reach is 5 feet horizontally and 8 feet vertically.

Of course "other conducting surfaces" is a huge group.


Al Hildenbrand
Joined: Oct 2001
Posts: 597
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Member
After consulting with my inspection community here, I learned:

<OL TYPE=1>

[*] The UL Directory "General Information for Electrical Equipment" lists DIMMERS, GENERAL USE SWITCH (EOYX) and says: "The basic standard used to investigate products in this category is UL 20. 'General Use Snap Switches'." That is, a dimmer is a snap switch.

[*] An assembly at an ungrounded snap switch wall case will be accepted if there are no exposed conductive surfaces on it or protruding from it (cover screw heads are ignored).
</OL>

So, the answer to my question above appears to be H, Choose only from A and E.

B has a conductive metal shaft that protrudes when the knob is lost or broken.

C has an exposed conductive touch plate.

D has exposed conductive cooling fins.


Al Hildenbrand

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