Design Safely mounting and connecting wall-mount decorative lighting onto a set

[strandcentury]

I am doing a show in which I require two wall-mount wall lamps (household type) to be mounted onto the set and connected safely. The fixtures will be using 30-40w bulbs.

I am dedicating a little 15A 4ch tree dimmer w/edison to power these wall-mount decorative fixtures.

I know how to install a light safely into a wall, I understand how to do that. But what about wiring?

What is the proper and 'to-code/safe' way of doing something like this?

 

[shiben]

I am doing a show in which I require two wall-mount wall lamps (household type) to be mounted onto the set and connected safely. The fixtures will be using 30-40w bulbs.

I am dedicating a little 15A 4ch tree dimmer w/edison to power these wall-mount decorative fixtures.

I know how to install a light safely into a wall, I understand how to do that. But what about wiring?

What is the proper and 'to-code/safe' way of doing something like this?

We would always do this:

Put a box on the back with a proper pass-thru for a 12/3 SO cable. Terminate the cable as desired.

 

[DuckJordan]

The wall fixtures should end in whichever plug your house uses either stage pin or Edison.

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[strandcentury]

So lamp mounted into front of set. Electrical box mounted to rear of set. Join to two together. Lamp is wired inside box with wire caps (like normal) to 12/3 SO wire which is then fed out through the proper sized pass-through on the electrical box and then cut to desired length and then wire to edison plug?

If correct. Sounds good to me. Thanks.

We would always do this:

Put a box on the back with a proper pass-thru for a 12/3 SO cable. Terminate the cable as desired.

 

[DuckJordan]

Sounds good

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[shiben]

So lamp mounted into front of set. Electrical box mounted to rear of set. Join to two together. Lamp is wired inside box with wire caps (like normal) to 12/3 SO wire which is then fed out through the proper sized pass-through on the electrical box and then cut to desired length and then wire to edison plug?

If correct. Sounds good to me. Thanks.

That is correct. Usually we would mount the box and fixture on a 2x4 or other dimensional lumber with a hole cut in it for the wires so as you could put it anywhere on the flat, not just next to a rail.

 

[strandcentury]

What about wiring? Common onto one of the prongs and then hot onto the other? The ground then goes to the third prong of the plug?

Or can it be grounded directly to the metal box and just use two prong plug?

That is correct. Usually we would mount the box and fixture on a 2x4 or other dimensional lumber with a hole cut in it for the wires so as you could put it anywhere on the flat, not just next to a rail.

 

[Les]

What about wiring? Common onto one of the prongs and then hot onto the other? The ground then goes to the third prong of the plug?

Or can it be grounded directly to the metal box and just use two prong plug?

It would be better to use a grounded cord as the box won't normally be grounded to anything if it's used on a set. Houses used to be done this way as they frequently used metallic conduit which was (in theory) grounded. Now, the practice is against code, but existing 2-wire systems may be grandfathered in. The only way you can get away with it in residential wiring these days is because a metallic box may be grounded using 2-conductor + ground Romex. The ground wire from the Romex will be bonded to the box, and the fixture can be bonded either to the box or preferably, directly to the Romex's ground wire. If I'm connecting a fixture to a metallic box in my house, and the electricians left a pigtail from where they wrapped the ground wire around the green ground screw in the box, I will usually bond the fixture's ground to the pigtail for good measure as you can't always assume that the box will be properly grounded, or that the screws holding your fixture will provide a sufficient electrical path.

If you don't ground your metal box, and you ground the fixture to this box, you are basically creating an extension of the fixture, and current still doesn't have anywhere to go in the event of a fault.

That said, a lot of people use zip-cord, which is basically lamp cord. Even so, it is better to ground something if at all possible.

Hot to narrow blade (copper colored terminal), neutral (socket shell) to wide blade (silver terminal). In other words, black to copper, white to silver.

 

[cpf]

What about wiring? Common onto one of the prongs and then hot onto the other? The ground then goes to the third prong of the plug?

Or can it be grounded directly to the metal box and just use two prong plug?

Edit: Oops, tapatalk nuked the majority of my response, and now I see Les's post covered it, move along.

 

[strandcentury]

Should the box have any sort of wire clamp/connector on the side? 12/3 SO cable is quite thick and heavy. I would put some sort of clamp on the side?

And would a typical "cap" type plug be okay? (like this http://www.homedepot.ca/product/3-wire-cap-plug-ebony/903844

http://www.homedepot.ca/product/3-wire-cap-plug-ebony/903844

It would be better to use a grounded cord as the box won't normally be grounded to anything if it's used on a set. Houses used to be done this way as they frequently used metallic conduit which was (in theory) grounded. Now, the practice is against code, but existing 2-wire systems may be grandfathered in. The only way you can get away with it in residential wiring these days is because a metallic box may be grounded using 2-conductor + ground Romex. The ground wire from the Romex will be bonded to the box, and the fixture can be bonded either to the box or preferably, directly to the Romex's ground wire. If I'm connecting a fixture to a metallic box in my house, and the electricians left a pigtail from where they wrapped the ground wire around the green ground screw in the box, I will usually bond the fixture's ground to the pigtail for good measure as you can't always assume that the box will be properly grounded, or that the screws holding your fixture will provide a sufficient electrical path.

If you don't ground your metal box, and you ground the fixture to this box, you are basically creating an extension of the fixture, and current still doesn't have anywhere to go in the event of a fault.

That said, a lot of people use zip-cord, which is basically lamp cord. Even so, it is better to ground something if at all possible.

Hot to narrow blade (copper colored terminal), neutral (socket shell) to wide blade (silver terminal). In other words, black to copper, white to silver.

 

[derekleffew]

I am doing a show in which I require two wall-mount wall lamps ...

Is sconce the word you're seeking?

Should the box have any sort of wire clamp/connector on the side? 12/3 SO cable is quite thick and heavy. I would put some sort of clamp on the side?

Typically one would use what is called a "Romex connector" to provide bushing and strain-relief for the 12/3 SO cable.

Not appropriate for a portable box, but likely acceptable in this situation.

...And would a typical "cap" type plug be okay? (like this Leviton | 3 Wire Cap Plug, Ebony | Home Depot Canada)

That cord cap is old-fashioned, dangerous, and a pain in the neck to wire (and may not fit on 12/30 SO). Much prefer the Hubbell or Leviton 5266:

Electricity is dangerous. When in doubt, consult a qualified professional in person. Isn't there a professor, technical director, or someone's dad who is an electrician who can help you with this? Internet forums can only get one so far.

 

[strandcentury]

I know at least three qualified electricians. I will consult with them first. Just wished to know how this was done in stage. It is a little unconventional.

Cheers,

Is sconce the word you're seeking?

Typically one would use what is called a "Romex connector" to provide bushing and strain-relief for the 12/3 SO cable.

Not appropriate for a portable box, but likely acceptable in this situation.

That cord cap is old-fashioned, dangerous, and a pain in the neck to wire (and may not fit on 12/30 SO). Much prefer the Hubbell or Leviton 5266:

Electricity is dangerous. When in doubt, consult a qualified professional in person. Isn't there a professor, technical director, or someone's dad who is an electrician who can help you with this? Internet forums can only get one so far.

 

[DuckJordan]

Actually its quite conventional 90% of shows come through have practicals setup similarly.

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[shiben]

I know at least three qualified electricians. I will consult with them first. Just wished to know how this was done in stage. It is a little unconventional.

Cheers,

Its not terribly unconventional, not because pretty much most shows do it, but because its basically like wiring a house, except you have a 12/3 SO cable with a plug on the end instead of a piece of Romex or if you are in Chicago, EMT to run 3x wires thru. Have on the of the electricians help you set these up, after that, you will know how to do it repeatably and wont have to ask them again. Also, use the plugs Derek recommended. Those others you found are a PITA for just about every situation.

 

[shiben]

What about wiring? Common onto one of the prongs and then hot onto the other? The ground then goes to the third prong of the plug?

Or can it be grounded directly to the metal box and just use two prong plug?

If its just a lamp, IIRC it does not matter which end of the lamp is hot and which is neutral, just so long as the ground is the same throughout.

 

[n1ist]

Actually, code requires that the center terminal of a standard screw-base lamp is hot, and the screw shell is neutral. You can contact the screw shell while removing or replacing the bulb, and if it is connected to the hot line, you could get a shock.
/mike

 

[shiben]

Actually, code requires that the center terminal of a standard screw-base lamp is hot, and the screw shell is neutral. You can contact the screw shell while removing or replacing the bulb, and if it is connected to the hot line, you could get a shock.
/mike

Interesting. I guess what my post really shows is that I have not wired tons of non-bipin gear lately...

 

[andy121]

Use box on the back with a proper cable

Thanks
Lilindo

 

[tdeater]

Everyone covered it well. We would do the same, a box installed into the flat or whatever, but for me for the cabling, I would normally use a surplussed computer power cord or something, cut the non Edison off and wire-nut that into the light in the box. We have lots of those cords lying around though. Then I would connect my lighting cord to that trough an adapter to my stage-pin cabling. If you do this often though, make up a couple of boxes with nice heavy duty connectors that you can re-use for shows.

 

[gafftapegreenia]

Many of the important points have been mentioned.

Just to reiterate, you should use a 3 wire cable (hot, neutral, ground), the ground should be connected to the fixture and to the box if one is using a metallic box.

I would also prefer that the connections inside the box be done with crimp terminals instead of wire nuts. Wire nuts are meant for permanent installation. Even though one might not consider the back of a set a portable installation, but it is certainly more exposed than a box in a wall. Sure, I've done this many times with wire nuts, but I prefer crimps.