sparky25

Have a custom job where 120v luminaires are being mounted to an all aluminum sign (good ol' screw in bulb base outdoor rated). The sign company is mounting the luminaires and the bulb holder has a copper ground lead.

The question is what is the proper NEC Section 250 way to ground the copper wire to the aluminum body of the sign? There are the standard 120v Black and White power wires connected to the chain of bulb holders but there were not any grouding wires run. Could they simply bond the multiple copper ground leads to the sign (is there a specific way) and gound the overall fixture?

Any input would be appreciated. This is a fixed sign, not a mobile and not subject to the GFCI sign section of the NEC.

Thanks!

raider1

Those luminaires must be connected to an equipment grounding conductor in accordance with 410.42(A) and 410.46 (2008 NEC section numbers).

The frame of the sign is not an approved equipmnet grounding conductor as listed in 250.118.

Chris

RIVETER

Raider1 is correct about the proper equipment grounding conductor; once that is achieved the shell of the fixture itself must be BONDED TO IT as well as the individual copper bonding wires. Also, in re-work such as that
you must make sure that the neutrals are not bonded,to the equipment ground at the fixture.We all know that the neutral is at ground potential, but only physically tied to it at the service.

brian john

Actually if there is load on the circuit the neutral is not at ground potential.

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Magnettica

The sign is going to need a connection to an intentionally constructed, permanent, low-impedance electrically conductive path designed and intended to carry current under ground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of the overcurrent protective device or ground fault detectors on high-impedance grounded systems.

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mcclary's electrical

Don't copy&paste, Magnettica!!,,,We can tell that's not your wording.

william1978

Welcome to the forum, and Raider1 has this one covered.

RIVETER

All statements are mostly correct except the one that says that if a neutral has a load on it,it is not at ground potential. The neutral will be at ground potential at all times in a grounded system; That system is one that has an actual circuit CONDUCTOR INTENTIONALLY GROUNDED TO THE SYSTEM GROUND . to limit the voltage to ground.
If at any time you try to read a potential from a neutral to ground there will not be one.

"Electricity has absolutely no use unless you have a difference of potential"

RIVETER

brian john

Riveter with all due respect YOU ARE not wrong on this.

Next time you have load on a circuit measure the difference between neutral and ground at the load. Do you have measurable voltage? Yes and why do you have voltage , because all conductors have resistance and therefore voltage drop, which results in a measurable difference in voltage between the neutral/grounded conductor and ground.

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brian john

NO, oh yeah you were right?

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