AFCI confusion

al hildenbrand · Apr 5, 2004

Re: AFCI confusion

Thank you, Charlie B. I just figured out (finally remembered?) that a resistor is conductive like a metal, even though it is in the same periodic table column as silicon. A resistor's conductivity increases with temp fall. Therefore it isn't correct for me to assert that it is a semiconductor (whose conductivity increases with temp rise). Thankyou for helping, spurring me to this. A variable resistor used as a rheostat won't qualify for the definition of an electron device.

It is interesting to note that the IEEE Standard Dictionary Of Electrical and Electronic Terms lists:

Electronic. Of, or pertaining to, devices, circuits, or systems utilizing electron devices. Examples: Electronic control, electronic equipment, electronic instrument, and electronic circuit. See: electron device

Electron Device. A device in which conduction is principally by electrons moving through a vacuum, gas, or semiconductor.

Noting:

Originally posted by Charlie B.: Once you alter the nature of a sine wave, by performing any switching on a ?part cycle on, part cycle off? basis, then you are definitely into electronics.

The altering of the sine wave, to me, is not the salient point, but rather:

Electron Device. A device in which conduction is principally by electrons moving through a vacuum, gas, or semiconductor.

Clearly, then:

The comodity 125 V 600 W incandescant only semiconductor dimmer (black in, black out) that costs $7.00 at the corner hardware store has a semiconductor that is the principal conductor, while the dimmer acts as a dimmer.
The semiconductor based dimmer switch uses electron devices for electronic purpose,
A dimmer switch meets the definition of ?utilization equipment,? and
A box that houses a dimmer switch meets the definition of ?outlet.?

Proven As Stated.

charlie b · Apr 6, 2004

Re: AFCI confusion

Al. I must admit that this has been an interesting technical discussion. I must also thank you for conceding the one and only point that I have been trying to promote.

Originally posted by al hildenbrand: A variable resistor used as a rheostat won't qualify for the definition of an electron device.

For my part, I will concede (and had never argued against) the point that a device that uses electronic components to alter or control the signal or waveform should be treated as ?utilization equipment.?

That being said, the only time I ever recall having disassembled a dimmer switch, all it had was a sweeping arm in contact with a wire-wound resistor. It contained no semiconductor materials. I have two devices at home that have dimmer-style switches. I don?t plan on taking them apart, but I would be very surprised to find a semiconductor playing a role in their operation.

So to re-state my position, but this time making clear that I am only speaking of a dimmer switch that consists of a variable resistor (i.e., a rheostat),

Originally posted by charlie b:


A dimmer switch is not an electronic device,

A dimmer switch fails to meet the definition of ?utilization equipment,? and

A box that houses a dimmer switch fails to meet the definition of ?outlet.?

QED.

al hildenbrand · Apr 7, 2004

Re: AFCI confusion

The only rheostats that I've found in 26 years of electrical contracting were a pair that were in a high end 1950s rambler controlling living room indirect lighting, fluorescent strips in a tiered coffer at the ceiling. They were controlling roughly 600 VA of load, each. Because of the amount of heat these wire wound units dissipated when dimming, they were mounted in large cast aluminum housings 3?" deep and had cover plates about 12" square. The rheostats had been originally installed facing into a large walkin closet adjacent to the living room as an "interior decorating" decision. I was hired to replace them with electrically equivalent devices and to mount then on the other side of the wall, in the living room. The solid state dimmers I installed fit into a standard two gang wall case with a conventional plastic cover plate that matched the rest of the outlets and switches in the dwelling.

My client was overjoyed to be able to adjust the lights while in the livingroom.

But that, really, is a topic for another area of the Forum. I'm interested in the continuing discussion about 210.12(B) with respect to a simple switch loop at a wall case.

For purpose of this discussion, keeping it simple makes the most interesting point, to me. . .so, the switch box has a simple 14/2 NM-B switch loop entering it, no other wires. The switch loop white conductor is reidentified. The ground wire is either unused and folded to the back of the box, or, is connected to the dimmer's ground. Oh, yeah. . .the dimmer. It's a standard 600 W 125 V incandescant only solid state dimmer using semiconductors to control a 100 watt incandescant luminaire. The dimmer has two black leads, one connected to the reidentified white conductor, the other connected to the black switch leg.

This semiconductor based dimmer is utilization equipment, by the Article 100 definition. The semiconductor based dimmer location is an outlet. The dimmer takes current where no neutral or other phase conductor is present in the switch box, because the dimmer is using the luminaire and its connection to a neutral in order to return current to the energy source.

The dimmer is in series with the luminaire with a section of wiring system between them, the dimmer takes current and the luminaire returns the current to the source.

Simple two wire (black in, black out) occupancy sensors and electronic timer switches may be substituted for the dimmer described above.

The point is, it seems to me, the two (the electronic device and the luminaire) exist in relationship with each other even when a section of wiring system separates them.

al hildenbrand · Apr 9, 2004

Re: AFCI confusion

Beside being two utilization equipment in series with each other, the relationship between the electronic dimmer switch and the luminaire is that of control. The electronic dimmer controls the operation of the luminaire by being in the circuit between the supply and the utilization equipment.

I am now talking specifically about a single pole 600 W 125 V semiconductor dimmer mounted in a wall case inside the bedroom beside the closet door, and controlling a single 100 W incandescent luminaire on the ceiling of a large walkin closet that has one door connecting it to that bedroom.

The dimmer is a proportional control system connected between the supply and the load.
The luminaire must take current on the supply side of the dimmer, in order to be under the control of the dimmer.

A snap switch is also a control system, a simple on - off two step control system.

The controlled system is the luminaire and the ultimately controlled variable is the illumination given to the closet by the luminaire. Whether the illumination is on or off, or at a "dimmed" value, the point is still the same.

A snap switch is installed at an outlet.

[ April 09, 2004, 11:06 AM: Message edited by: al hildenbrand ]

highkvoltage · Apr 22, 2004

Re: AFCI confusion

I have enjoy this discussion very much. Here our local inspectors require all outlets and switches in a bedroom to be AFCI protected. They claim that even when you upgrade an older house that has tube and knob if that circuit passes through the bedroom for the light and that is all it is for is lighting and continues to the rest of the lighting in the house it has to be AFCI protected. With some older home all the first floor light was on one circuit and the second floor lighting was on another circuit. At the 2002 NEC class they reinforced this also. It is very interesting to me how the code is interpreted differently in different areas of the country. Thank you all very much for covering this subject so objectively.

AFCI confusion

al hildenbrand

Senior Member

charlie b

Moderator

al hildenbrand

Senior Member

al hildenbrand

Senior Member

highkvoltage

Senior Member