a wiring conundrum...

[LightinGal]

Ok, heres the deal:

For my next show, the set designer is building a false proscenium. It is 10 feet high and 20 feet wide. We are going to put lightbulbs (60 watt) about every 18 inches. I can wire it once I have the stuff, but what kind of wire and outlets do i need? I knew what kind of outlets i needed but when i went to the good ole home depot, i found out they dont make them anymore. SO this leaves me lost as to what kind of outlet and wire i need.

any help?

[Peter]

On one of my more recent walks past my dad's work bench I happened to see a couple of things that were bascily a screw in type light bulb receptical (like you would see on a table lamp) with a two prong plug comming out of the other end (just like you would plug into an extension cord). They looked fairly new so I am asumeing you can buy them in some kinda hardware store. Then it would just be a matter of plugging them into extension cords. I am thinking that maybe you could use the kind of cords that have two female plugs on the end, pluging the light into one of the plugs and the next extension cord into the other, although I dont think I would run too too many of them off of a single line like this. I am sure others will be by with more specific answers, but that's my idea and hopefully others can point out what is unsafe about it so I learn too!

[falcon]

How bright do you want the lights and how many will there be? Theoretically, you can put all the lights onto one circuit, but they all will be dim. Its pretty much a matter of current vs resistance. Assuming you are plugging into a standard 110 volt outlet, the resistance of each bulb is about 200 ohms of resistance? adding up all the total resistance assuming you doing wire them in parallel, which would be difficult with extension cords they will be pretty dim lights. Or your better option is to plug into your dimmers. Again assuming here, that the dimmers are 2400 watts, theoretically, you can get 40 lights per dimmer, again, i wouldn't go that high personnally. As for installation of them, just buy standard sockets that have an edison plug on them and run extension cords between them, or if you are good at wiring, buy the sockets themselves and run romex wire between them and at the end put a twistlock plug for the power supply. Typicallay, these are ran back to the breaker box, but the plug will substitute just fine. In standard wiring, as a rule, there shoulding be more than 12 items on each circuit, so keep that in mind. Personnally I wouldn't do more than 12, so just be careful. Less would be better in this case. And remember I am only talking theoretically here. So practically this might not work. But if it was me doing this, i would run through the dimmers with 12 lights on each circuit.

[LightinGal]

ok, I would not want to do the extension cord thing just becuase i will have so many lights. I will be wiring them in 3 sets so i can do a flicker effect. what i would ideally like to do is get some zip and sockets and just wire them together and then run them to a twistlock plug and put them into my dimmers so i can program them into cues and such. I guess my real question in what kind of wire do i need and how many lights can i fit on one run? I will have many many lights. and i would want them to be about 60watts.

[Mayhem]

Well as Falcon correctly stated, if you have a 20A feed (2400W) then you can run up to 40 lights (at 60W per light).

NOW - I am in Australia and having glossed through your NEC book, I know that the differences between Australia and the US are far to great for me to feel confident in answering the second part of your question. So, as for the wire that you should use in this situation, you will need to either call a local electrician or wait until someone else comments. However, you may wish to ask someone qualified in your area.

[falcon]

for wire, i know here in Canada, your standard romex wire, which is used in houses with wood framing is sufficient, but the thicker the wire, the more current it can carry, best to go to your local home depot and ask their electricians about the best wire, and mention whether it is going agains something metal or wood. this makes a difference, builidng codes here call for romex in wood structures and bx? (wires in a flexable metal insulator) in metal.

As for how many lights in each run, take the dimmer wattage and divide by 60 and you should get the MAX number of lights per circuit. Don't max out the circuit though.

If i was in your position, i would go to home depot or similar store and tell them what you want to do and make sure you mention you the dimmer wattages and that it plugs into a twistlock circuit, they should be able to set you up easily.

[ricc0luke]

Its a semi-permament install so you can go with just regular romex instead of the normal 12/3 so cable...

romex is the type of wire used in construstion... 12ga. romex can carry 20 amps... so you should be fine there... also, i would on the end if you put a plug... use a section of 12/3 SO cable instead of romex, it is the safter, smarter thing todo.

know that often times when you buy romex, it will say 12/2, even though it really has a hot, netural, and a ground. in romex, the hot and neutral has insulation around them each indivdualy, but the ground does not, so i guess thats why it is 12/2 even though it has the ground, but it is all encased in an other jacket... anyway... moving on...

your gonna wanna pick up a ton of those little wing type things that you use to connect wires... use on of those and then wrap it with electric tape.... don't just use electric tape, bad things always happen (to me anyway).

but i would definately use a peice of 12/3 SO cable on the end you put a plug on.

[eamon]

hi

It sounds like what you want is festoon cabling. You can buy the stuff made up with moulded sockets with X amount of holders for X distance. They are used in the contruction industry and christmas displays. Ah hell they are pretty much used everywhere.
All you have to do then is wire them to a suitable plug and switch on.

of course this might be the expensive option


eamon

[koncept]

from my experience, ricc0luke is correct, use a 12/2 romex with ground. most electricians do not put more than 10 outlets/lights to a 20amp curcuit. i would say stick to that. at most big home improvement stores (i think home depot has them) they have a clip on light socket as someone mentioned above.

Not to contradict you ricc0luke, but i have ran romex into several different plugs with no problem, the trick is clamping the cable inplace...


eamon: i like your idea but i have no clue where you could get that around where i live.
going with eamon's idea You could try going to a construction site and asking if you could borrow a couple sets for your show.

http://www.foxelectricsupply.com/con...qshCatId=26162

i would ask at home depot if they have those (i dont know what the socket part is called)

[eamon]

hi again

I would check in your local electrical store or lighting hire shop. They are bound to have a knowledge of them. You can wire them up yourself but it is getting harder to find the parts. Suppliers only wish to sell them moulded. Trying to reduce the idiot factor or PEBCAC.......
Problem Exists Between Chair And Console.

As I am in Ireland I would not even know where to look in the US

best of luck

eamon

[ship]

So I’m going to post a reply, and let me be specific that it’s part of the living I have to do such a thing, but I’m going to hold off in my advice for now given the weekend coming up, much less my once a year show in the morning. I hope others can refine their ideas further or present new ones. Still some problems exist in now that you have a type of but not the only type of lamp bases so far presented, how than do you make a chase effect on the proscenium opening that’s mounted to it. Much less lots of other details as to how and where to do the splicing - given these are the only lamp base types on the market, and how to wire for the chase.

What is also very important and not specified is the exact number of 60w lamps. Does the effect only cover the 20' width or also it’s 10' high sides at 18" on center and three circuits? Also there is a big difference in both lamp and gear needed if a true strobe verses just chase effect. This needs to also be refined. A strobed lamp cannot be left on long by design thus the wire gauge often can be less. On the other hand, such bursts and collection of energy for the burst of light internally can destroy a dimmer. For a chase, it’s just running from lamp to lamp to lamp at the speed the dimmers can turn them on or off. Given they have to be dimmers. In any case, since there could be a mistake, full amperage should be factored in.

[Spelling and some words corrected for in quoting below.] Just helping to brain storm or production meeting with the people presenting ideas. The questions I raise are intended for those asking to further flush out their ideas. Otherwise in me not yet stating a specific method I am hoping to foster more discussion. How soon do you need to draw up a bill of materials for the project?

Project Goals:
“a false proscenium. It is 10 feet high and 20 feet wide. We are going to put light bulbs (60 watt) about every 18 inches”
“I will be wiring them in 3 sets so i can do a flicker effect.” [Chase Effect]

“what i would ideally like to do is get some zip [cord] and [lamp] sockets and just wire them together, then run them to a twist lock plug and put them into my dimmers so i can program them into cues and such.”
“I guess my real question in what kind of wire do I need and how many lamps can I fit on one run? I will have many many lights. and I would want them to be about 60watts.”

-Are you mounting the outlets on the exposed surface of the proscenium or rear mounting them?
-If face mounted lamp, - assuming so in seeing the lamps, do you just want to see lamps or is surface mounted lamp bases and wiring permissible?
-What’s your budget and skill level? Who is supervising this project as far of skill and safety level?
-Are you going to have somewhere behind that is not accessible and sealed, or do the lamp sockets need to protect from accidental contact?
-Heat, heat, heat. For surface, wireway, lamp base, wires feeding and materials near even if chase effect - plan on all being on at the same time for a prolonged period of time out of safety.
-Given you could not find what you had in mind to wire with, can you specify what you had in mind? Very rare even of a home center no longer carries it, that something is not still available thru other sources. Otherwise, what means of mounting and wiring as far as attachment of conductors do you intend?


Some questions in replies:
“I am thinking that maybe you could use the kind of cords that have two female plugs (?connectors/receptacles/outlets) on the end”
-??? Normally there would be three outlets. Wire gauge for both voltage drop and amps is important in generalization. A “plug” is the male end. Two plugs would be bad.

“Theoretically, you can put all the lights onto one circuit, but they all will be dim.”
-??? What basis do you have for this? A circuit breaker capacity has little to do with the intensity of the lamps. Do you mean “Voltage Drop” for the calculation?

“Its pretty much a matter of current vs resistance.”
- Distance and wire gauge figure into this above somewhere as important. “the thicker the wire, the more current it can carry.”

“Assuming you are plugging into a standard 110 volt outlet, the resistance of each bulb is about 200 ohms of resistance? adding up all the total resistance assuming you doing wire them in parallel, ... they will be pretty dim lights. Or your better option is to plug into your dimmers. Again assuming here, that the dimmers are 2400 watts, theoretically, you can get 40 lights per dimmer, again, I wouldn't go that high personally.”
- Where is the difference between a 120v outlet and a 120v outlet off a dimmer that makes one system dim and the other one at intended intensity? Has resistance of lamps suddenly dropped because it’s powered from a dimmer instead of wall outlet?

“run romex wire between them and at the end put a twist lock plug for the power supply.”
- Installing a plug on solid wire is a bad thing. Why the twist lock plug over any other type of plug?

“but I would defiantly use a piece of 12/3 SO cable on the end you put a plug on.” “Not to contradict, but I have run Romex into several different plugs with no problem, the trick is clamping the cable in place...”
-So than it’s a trick to what, ensure that you correctly apply pressure to a solid wire so as to both achieve proper conductivity, but don’t cut into the conductor so as to make resistance and break the solid wire? Interesting, what’s your method for doing so? I assume that you are using home owner grade plugs in an industrial situation. This so as to wrap the solid wire around the screw terminal as per a normal building wire type duplex receptacle. This as opposed to a plug’s clamp intending to compress and grip the conductors tightly so as to ensure that as the metal expands and contracts with heat/current it is not loose thus a high resistance connection. How flexible is this solid core wire - meaning how many times can you plug and un-plug it before constant flexing of the building wire causes it to break? If a special technique, while separate discussion please go into it.

“Typically, these are ran back to the breaker box, but the plug will substitute just fine. In standard wiring, as a rule, there shouldn’t be more than 12 items on each circuit, so keep that in mind.”
- So in one sense, installing a plug on Romex wire is un-standard but “just fine,” in another sense you should keep in mind the rule about 12 things on each circuit as “In standard wiring.” This typical wiring, is it specifying how many receptacles on a circuit or is it all inclusive as to say how many lamps say in a dressing room you can have on the same make up mirror lighting circuit? Given often 12 or more incandescent lamps in use on sets of makeup mirrors in the makeup room than are they also a exception or should each set of 12 have it’s own circuit breaker? Remember that even if you do a bunch of switches, it’s still the same circuit.

“Personably I wouldn't do more than 12, so just be careful. Less would be better in this case. And remember I am only talking theoretically here. So practically this might not work. But if it was me doing this, i would run through the dimmers with 12 lights on each circuit.”
- Twelve 60w lamps on a 2,400 watt dimmer, thus you need three of them?

“best to go to your local home depot and ask their electricians”
-EEK!!! They are neither electrician, nor can you often find someone with more a base of knowledge than wiring a receptacle - almost up to current code at least - something about that required grounding wire most often forgotten. Go to a real electrical supply store for advice or contact a licenced electrician as the more correct options. Advice is often free, or you might even get some real support and help for free. Thing is, either of the above two, and bear with the electrical house counter people ignoring you, intimidating you, and seeming less than friendly or interesting up until the point they completely understand your intent. Once understood and as worried as I, you are now their responsibility to ensure what you do is safe and proper at very least. Better than this, E-Mail your intent to a sales person at the electrical supply house. Often those of the sales staff are not counter help and have more time to really help. “I would check in your local electrical store or lighting hire shop.”
You would not believe the advice and advice I frequently step into correcting of at Home Depot. Do not base your other than most basic wiring advice from "the Helpful Hardware Man." While some will be compitent and able to think on their feet, and some might even know current NEC verses home owner guidelines, most won't have any clue as to what's what they might hack verses what you need to do. Be very cautious about home centers, I early on worked for two of them and did help in the electrical aisle at times. I absolutely had no clue - would you in question have an idea of what I assured you of for a most basic wiring concept verses those that really know what they are doing when just as confused? Do not chance this. Home Center people are best off telling you the difference between black and white wire at best for them or when not even that at times, pulling something down from an upper shelf. Look for the contractors shopping in the aisle - you know them, the people that have a clue and less wondering look on their face, instead those very clearly looking for something very specific, and ask them their background in helping you. Trust a electrician looking for a very specific part they are having trouble finding. Or better yet, educate yourself by training and reading to be that shill in the cable aisle that can't hold yourself back from laughing at the advice given more often than not.


“take the dimmer wattage and divide by 60 [the wattage] and you should get the MAX number of lamps per circuit. Don't max out the circuit though.” [80% is a good thing.]

“12ga. Romex can carry 20 amps... so you should be fine there... also, i would on the end if you put a plug... use a section of 12/3 SO cable instead of Romex, it is the safer, smarter thing to do.”
- Sounds good to me so far, do you mean wire the stranded wire to the first lamp base [dependant upon type] or some splicing box?

“your gonna wanna pick up a ton of those little wing type things that you use to connect wires... use on of those and then wrap it with electric tape.... don't just use electric tape, bad things always happen (to me anyway).”
- Do you mean wire nut? What size or color? So do you mean use electrical tape over the wire nut or don’t do so? Separate post, but what is it about electrical tape use - given a specific description of use and what goes wrong, what’s wrong with electrical tape? Assuming in this case, electrical tape is commonly used to wrap the wire to the wire nut so as to ensure the wire nut won’t come un-screwed. Was but is not current standard, though I often will still or not dependant upon the case. Or are you recommending not to do a splice without wire nut and only tape holding it together and safeting it? That would be wise advice and very bad practice.

“It sounds like what you want is festoon cabling. You can buy the stuff made up with molded sockets with X amount of holders for X distance. They are used in the construction industry and christmas displays. Ah hell they are pretty much used everywhere.
All you have to do then is wire them to a suitable plug and switch on.

of course this might be the expensive option.”
- I agree to some extent though that might be a source to look into for parts and ideas in being cheaper to do it yourself. The spacing of lamps and circuitry is very well defined otherwise. Also some on the sign company websites might in doing chase effects might be of interest. In festoon wiring however, it’s designed to be a stringer of lamps hung from the cord between two distances. How than do you mount these to the proscenium? Sources like Lex Products or TMB would have stage rugged types of lamp stringers, otherwise the Grainger types would have the construction standard types. Is such a stringer best?

Lamp Base options so far presented:
“basically a screw in type light bulb receptacle (...) with a two prong plug coming out of the other end” & “just buy standard sockets that have an Edison plug on them” [same thing]
- Normally a weatherproof festoon lamp socket will have a rubber molding around the wiring splice to base and lamp base with two stranded wire leads coming out of it or the next type below.

“at most big home improvement stores (I think Home Depot has them) they have a clip on light socket”
- Clip light lamp sockets will be different in being plastic lamp base (temperature rating) and zip cord to a NEMA 1-15 two prong Edison plug - polarized or not. Polarized plugs being a good thing of course.

Wiring options so far presented:
“Then it would just be a matter of plugging them into extension cords. I am thinking that maybe you could use the kind of cords that have two female plugs on the end, plugging the light into one of the plugs and the next extension cord into the other,..” and “run extension cords between them”.

“run Romex wire between them and at the end put a twistlock plug for the power supply.”

[ship]

The above questions on my part are not saying good or bad per say, nor saying that those that have posted their thoughts is not a great thing, or that they are stupid for doing so. This one post is the intent of the forum in many so far having helped others good or bad in advice, still the ideas and kernels of knowledge are expressed in an attempt to help. Even if 99% in the worst of conditions is wrong, one should not fear expressing their thoughts because all it takes is that 1% for great inspiration to happen. This and unless you post your response, how do you know if your own method is a good idea or not short of endless study you should do but at times have to implement before you learn better? Even the asbestos re-wiring for me, I’m changing the system or extent I would follow intent as of others stating good reasons my solution was not wise. Discussion is good for all.

Yes, in quoting some ideas, I’m being hard as it were on the ideas you express at times or seemingly supporting others. Not completely but there has been some good advice so far in details or consideration of them in the project in my opinion. Would you rather that nobody challenged you in thinking about how you would do so? Much more time to think about response on-line verses at the moment. This is practice for otherwise being walked over in a production meeting or in dealing with a crew. You have an idea, support it or admit it’s probably wrong and get beyond it in finding a better solution. As tech, no offense should ever come to play.

Do not respond to this now statement off topic, instead, do more thought onto either supporting your ideas further with why it’s the correct with more detailed solution or recognize the problems expressed with the on the spot solution and come up with a better solution in having problems presented and more time to think.

I hope that all responding so far refine their ideas and express them again in having something more concrete and refined. Much less even those non-members or less active members, since it’s both wiring and safety, many others will also add their thoughts. To the silent thousand people, have you ever done something like this? If so how? If not what do you think? Don’t just be a reader, there is no stupid answer, just the question not asked and statement not expressed. You can be assured that between Len, DMX Tools, Wolf, Myself and many others in the US and elsewhere (and not intending to short others that I am shorting but not intending to) that there is a safety factor here with this - discussion. Also in the intent and good start, I might recommend that more expert level advice to the problem wait a day or two before posting. I won’t before say Sunday night. Should you feel expert, post or wait but please post at some point. Hopefully with other things in design statement that need to be refined such as dimmer capacity, but otherwise in what parts and methods used you hold off just a bit as I will. (This or also in my place so far also help those with an idea flush it out further we are all hoped to do. Not in direct yes or no challenge but in raising problems and asking that they support the idea tactfully.) There are many ways to do something often. This project will both come up again on the forum and to all tech people in life. Good discussion to learn from - most especially from many sources all included.

[koncept]

“but I would defiantly use a piece of 12/3 SO cable on the end you put a plug on.” “Not to contradict, but I have run Romex into several different plugs with no problem, the trick is clamping the cable in place...”
-So than it’s a trick to what, ensure that you correctly apply pressure to a solid wire so as to both achieve proper conductivity, but don’t cut into the conductor so as to make resistance and break the solid wire? Interesting, what’s your method for doing so? I assume that you are using home owner grade plugs in an industrial situation. This so as to wrap the solid wire around the screw terminal as per a normal building wire type duplex receptacle. This as opposed to a plug’s clamp intending to compress and grip the conductors tightly so as to ensure that as the metal expands and contracts with heat/current it is not loose thus a high resistance connection. How flexible is this solid core wire - meaning how many times can you plug and un-plug it before constant flexing of the building wire causes it to break? If a special technique, while separate discussion please go into it.

when i have run solid wire into plugs, i have used (i dont know what type, but was working with a certified electrican (currently a building commisioner)) and the plug had a clamp type setup. so instead of wraping it around the screw on the side of a light switch or outlet, it was more like a curcuit breaker where you tighten the screw and it clamps down.

As far as the 12/3 SO cabling goes, i have done that as well, with that i have used a juntion/splice box and if i remember correctly the beige wire nuts.

on a note to ship: These long posts are a killer to read but have been very valuable. Second, i like that someone is challenging what i have said, it makes me wonder if what i have thought to be correct for a few years now is wrong, if it is i would like to be corrected. (even though i might not like being wrong..)

[ship]

Nobody likes to be wrong. Sorry they are long and I like to learn also. On Asbestos, my origional method however is wrong for all but very important equipment to save in-tact. Some amount of stand off on my side of fixture verses replacement of entire cap is still lingering but this is movement on my part in being no better than anyone else. You stop learning and changing your methods, you are of no service to yourself or others. Constantly learning is much better.



Just in a constant and continued debate today with the other ME at the shop today.

In the past and as our standard we use L21-30 plugged cable with 8/5 wire on it for our three phase hoist systems. It has three phases of power and is by way of plugs, 30 amps maximum load. The 8/5 wire should be somewhere around 45 amps in capacity. Hist intent is to continue using that system he no doubt set up in part by way of voltage drop to ensure it will not burn up. That's a good and noble thing. Good system to over-rate your cable for maximum load on long lengths - kind of required to at least consider.

I started using 10/5 that's "found cable" from other lighting companies for the 25' and less lengths of this type of cable. 10/5 is rated for 30 Amps, so is the plug. Voltage drop in this short of distance is nothing much to calculate. Much less the rest of the industry uses this cable and when not labeled, I have to keep it thus have stacks of it. While I'm not intending to even use it in 50' lenghts that others do, it would seem to me that at 10 to 25', having a cable rated for no less than that of the plug should not be a problem.

Even if a 25' were added to a 50' than in making a 75', it still would be no problem because of the lack of voltage drop on the 50' length.

Tradition verses logic, I always win during the debate but it's a constant fight as to my logic. Never much beyond tradition on his part.

In any case, we do debate the merit of it or even the use of 10/5 on 400' lengths for 20 amp circuits we are both somewhat concerned about TBA.

On the other hand, where specific to NEC such as I am very certain you will find, or does not make much sense enough to debate, that person without any standing does change and develp a even better method. We debate a lot and as opposed to the 20 years in the shop before I got there, he finds me useful to act as his safety net just as I for him.

"when i have run solid wire into plugs, i have used (i dont know what type, but was working with a certified electrican (currently a building commisioner)) "

Solid wire into plug is very bad practice no matter who is advising it's use. Should you wish, I have NEC 2002 Handbook and can do a bit of research into the specific ruling on such a concept. Otherwise believe me, just as while I know a fair amount of wiring but am not in any sense a master in all forms of ding it, that those that advise the use of it can be wrong in a detail or what works for them so far in not having been taught or learned different. A solid wire, no matter the type in going into a plug is first not a flexible wire that by defination is specified for use on plugs, nor is intent for that type of clamp no matter the plug. Yes it's done, is it proper - no.

I know guys that are expert in their field, and they are, yet they have never once picked up the NEC. Much less if they have, just as I in not learning specific sections well enough at times, what they think ok, is at times not. Ever read the NEC? It's huge and boring. No matter the experience or pedigree, it is and never should be any statement that you know all and can rest on your lorals. This especially when questioned.

Ask again the inspector and electrician about the use of solid core wire inside a plug. You might see them defend the use, after a few moments hesitation, but it no doubt will be with some form of "in this situation" type escape. Otherwise in the poing and problem brought up they will re-think, deny or find that they were just as anyone else doing a mistake. You would not believe the mistakes I have made over the years or even still make. Point is never in being perfect, it's in doing the absolute best you can. For a specific application and use, sure throw a plug on it.

On the other hand, in being proper and what you need to always do, what than is the advice? You will never beyond what they have said OK, find a solid wire inside a plug. Why is this?

[cutlunch]

Hi. I am not sure about the States but I would go with the festoon idea. Here we have bulb holders that have pins in them that pierce the the conductors in the wire when they are scewed down onto the cable. We use the same rated wire as used in running the lights in a house. This is the simplest way to get the spacing right. Just make up the three circuits with each wire running near the others and paint over them when they paint the proscenium. If this is not good enough drill two holes, one just each side of where the light needs to go to run the cable through and back. Just from a rough calculation three circuits will be less then half the load on each of their dimmer channels.

[LightinGal]

yes cutlunch, yes. I know exactly what you are talking about and thats what I want to do. The sockets you are talking about (add-a-taps) are exactly what I want to use and I believe the wire your talking about is lamp wire? I recently talked to a friend about my problem and we refered back to a show that we did. Ok, so I went to home depot and couldnt find the add-a-taps, so I got a keyless porcelain lampholder. I think these will do the trick, but let me know if I am wrong!

Thanks everyone!!

[MSwan]

Let's look at this from an electrical stand point:
10' each side and 20' over the top gives us 40' total
40 *12 = 480 this is the total inches to cover
480 / 18 = 26.666 (lets just say 30 since this is how many lamps are needed total)
3 circuits for 30 lamps gives 10 lamps per circuit
60W*10 = 600W
600W / 110V = 5.45A (I know it is actaully 120V but that gives us a safety margin)
most zip cord (aka lamp cord) is at least 16AWG I don't rember the exact current rating per NEC on 16AWG but I know 12AWG is 20A.

From an electrical stand point the use of zip cord and add-a-taps (which if you Google you will find many suppliers) is totally fine. If, however you have a stickler of a Fire Marshall you may have to use 'real' wire which will be a royal pain but you can get the same wiring pattern.

just my 2¢.

[ship]

Assuming we are talking about the Edison type plugs and receptacles that are commonly used with zip cord, because some forms of medium screw lamp base are also called Add A Tap at times. A Polorized Add A Tap connectors such as the #2606-BK and #2601-BK plugs would be recommended given polorized lamp bases they would be powering up. I believe these are Leviton part numbers but could be Eagle Electric otherwise.

A Add A Tap will only fit 18-2 SPT-1 wire. It is not physically possible to fit either 18-2 SPT-2 or even 16-2 SPT-1 wire within the connector if using it properly.



Can you read the brand and part number on the keyless porcelain lampholder so we are all on the same page?

[ship]

Ok, this is long but in response hopefully good information on the subject.

There has been some good discussion so far doing a three circuit incandescent lamp Chase effect to a scenery portal. I hope the discussion helped some in getting people to give further thought into how best to do this. Or as above in my questions or below, where they might re-think their initial concepts. As promised in holding off, here are my thoughts. I hope it is not too late to reconsider how you intend to do this wiring project.


Wiring and cabling requirements:

As described, 10' legs and a 20' opening with lamps 18" on center. I determine it to be 27 lamp sockets which equals nicely 9 lamps at 60w per circuit. This assuming a base voltage of 120v is 4.5 amps per circuit. Given a +40' length of wire at 4.5 amps (110v would be 4.9 amps as a range.) 18ga wire would be sufficient for a temporary install of a chase circuit of this amperage given the not more than 50' length. Note that I have not checked the actual recommended specifications or done the calculation on this but out of experience judge it to be safe loading. However due to the number of taps (added resistance), safety factor and minimum conductor sizing of stage cable specified to be 16ga wire, it than would be a better minimum wire gauge. This is not to say that you could not go larger still in wire gauge. Dependant upon the lamp base type, the wiring could be stranded or solid in running between lamp bases. This is very dependant upon lamp base type and means of mounting. This scenery is now a wiring device - one complete unit.

It also assumes that the scenery (now lighting fixture/device) will have a plug of some form - twist, stage or Edison where the power is fed into it. This type of outlet will not nor does it need to be grounded when mounted on an assumed wood fire resistant construction, but it must be polarized by way of using either polarized Edison plugs or grounded plugs that ensure the shell of the lamp base can not be plugged in backwards. By plugged in backwards, I mean the hot wire should never go to the screw shell of the lamp base. Normally use of a grounded plug for a un-grounded system would be against code and if Edison based, you should not given the availability of polarized non-grounded NEMA 1-15 plugs, not use a grounded Edison plug. But if using stage pin or twist based system, use of a grounded plug is acceptable to ensure safety of the system by way of polarization. Your local code or supervisor might require a short adaptor from polarized non-grounded to grounded house system otherwise as acceptable. While you might be able to find un-grounded stage pin plugs or remove the ground, since the use of that ground pin within the plug - even if nothing attached to it, ensures the proper polarization of the plug, such is acceptable. The non-grounded stage pin plugs just as non-polarized Edison plugs is not in this case of a medium screw based lamp acceptable for use.

There should not be a direct run of cable between the scenery and dimmer without a means of disconnection (plug) at the scenery which is now a lighting fixture or assembly by classification. Not only would such a direct run without plug not allow for service of the scenery by means of other than remote disconnect, but assuming normal 12ga stage cable is feeding the scenery, there will not be any extra distance of run to power in wire gauge of the chase effect needed to add to the minimum wire gauge on the scenery dependant upon distance to dimmer given the connection to the jumper is attached to a cord that is sufficient in it’s wire gauge for it’s length and load. Keep the scenery as a independent lighting fixture it is. You do not do a 50' run between a leko and dimmer pack without a jumper and plugs, this scenery is in portable or temporary wiring device similar in intent.

In my opinion, other than if the scenery needs to come apart or is constructed by way of separate components, no other plugs and receptacles should be used especially not in attaching the lamp base pig tails to feeding conductors. If it is to come apart or be installed in separate pre-wired components, than only what plugs and connectors necessary to make this done should be used. Otherwise use of plugs where not needed adds a unnecessary expense and potential for problems and hazzards for this assembly.

You are also required to install plugs only on stranded cable or fixture wire. Installation of a plug on a solid wire is not acceptable ever for production use. While you can use Romex, AC (often called BX), S, SJ, SJT, SPT, MTW, THHN, TW or what ever else is suitable between lamp sockets - dependant upon the socket type and installation or junction, you can only use cable of the S, SJ, SJT or SPT type in going to the plug as a cord feeding the assembly. It is also possible to use MTW inside of a fiberglass sleeve for it’s protection also as a fixture cord. For scenery, better than Romex is “Flat Marine Multi-Conductor Cable. It is very similar to Romex but stranded with MTW wire having an outer jacket. See McMaster #7589k11. Marine cable or MTW is an exception to normal even straned building wire in it having a thicker insulation and designed to be flexible in a constant sense. Stranded THHN and other types of building wire while also stranded is not designed to be flexible in a permanent other than installation and occasional sense and has a thin insulation. The MTW would need a fiberglass sleeve over it. The reason why you cannot just use whatever you wire the lamp bases with is because once it leaves the means of support and last lamp base mount, it is a fixture cord with it’s own requirements to code. You are not wiring between lamp bases, you are wiring the lighting fixture to a jumper cable. This wall is one large fixture thus you have a range of wire you can use as long as suitably supported and protected in a lamp base to lamp base part of it, but the fixture cord must comply with code in use since it’s not a mounted part of the fixture.

So we in the end have a system wiring of a minimum gauge of 16AWG between lamp bases - TBA the means of tap or splice, and a fixture cord rated cable at the power source for the scenery. Note that this is not yet going into the specific necessity of cable for your use which does depend upon lamp base type. A fuse or over current protection of the scenery - on the scenery is not necessary in the US for a temporary wood construction, but it would be wise if possible to fuse down it’s power source. Also a good idea might be GFCI protection. Neither are absolutely necessary but a good idea. This is my opinion and the local code or jurisdiction might require either or both of the above.

Since there will be 4.1/2 feet between lamp bases, and dependant upon the lamp base used, wiring can or cannot touch or be supported by the opposing lamp sockets, some amount of separation and support for conductors might be necessary. Otherwise in some cases it’s possible to just cable tie the wires to the lamp base or it’s mount. Seek supervision on this.




Lamp bases as a important factor:

There are ever so many types of E-26 or E-27 medium screw (Edison) screw based lamp base types on the market. So far bought or recommended it would seem are construction stringer, all weather type or rubber insulated lamp base with individual conductor wire leads (pigtails) off it, clip light type lamp bases that mount with SPT cord coming out of it, by means of “Hickey” - a bracket that mounts the base to the fixture or has a 1/4" I.D. lamp type screw fitting for support of it. Also mentioned and bought is the keyless porcelain or plastic lamp socket. None are designed for use in this surface mount to sign (as it qualifies) application but all can be made to work with such effort to some extent given that’s the best you can think of for solution. Separate however “can be made to work” from is it designed for or the best for this application? Keyless lamp holder is a general term normally meaning a 4" round lamp holder.

The rubber surrounded all weather lamp base (Leviton #124-D) has a molded flange to it that can be slipped thru a hole and siliconed in place as means of mounting. It’s not ideal but could work. The Hickey based lamp base can be mounted to the scenery to some extent in a other than strong way. A separate flanged hole than would be necessary for the actual wiring to feed thru. Note the flange hole as required - even if lumber is soft, you are not to feed wiring directly thru it. The 1/4" nipple based lampholder can be drilled thru the scenery and screwed to it’s backing given scenery no thicker than the length of the nipple. Various washers and lock washers will be needed to ensure it does not enlarge it’s means of mounting. This like the hickey mount would also be less than desirable as a strong secure means of mounting of the lamp base.
Other options such as stringer type assemblies in means of mount other than the above potentially are even harder to mount and less secure yet. Even a 60w lamp is hot enough to melt any form of hot melt glue if used as means of mounting which rules it out in just gluing the bases to the scenery.
The keyless lamp base - porcelain or not can be mounted with wiring under it but must be mounted to a at lest a low profile ½" thick round pancake box to as to assure wiring space and safety. Do not attempt to mount a keyless porcelain device without metallic wiring box behind it. Do not attempt to mount a keyless porcelain device without metallic wiring box behind it. Such a minimum clearance ½" pancake box is fed thru it’s rear and only meant to ensure that should there be a short, the lamp socket in very close contact with scenery will not start a fire. The actual purpose for such a box being on the market is exclusive for necessities in remodeling and due to wire space is not considered sufficient for normal use but in this case for a surface mounting but not splicing box, it would be ok for use in my opinion. You are not to attach any keyless porcelain sockets directly to scenery. Also of option is the feed thru keyless lamp sockets that have two mounting screws per terminal. In the above ½" pancake boxes while doubling the wire you are less doing a splice requiring three wires, and instead using an in and out directly that requires by far less room. This overall is a better idea for your application should it be your final use. Given it is, you will also at added expense need to use the pancake boxes to the face of the scenery in mounting. Drill thru the scenery at the rear of the box and use a mechanical strain relief for the wire, than once the box is mounted, attach the lamp base directly to this pancake box. Note this is a very narrow box, you cannot even use wire nuts inside it for the most part, it’s use is only to ensure that there is some space between lamp base terminal and scenery.

A different option would be to use normal octagon or pancake boxes to mount the lamp base to, but cut a hole in the sign’s surface just as you would for a drywall installation. All surfaces - including the cut hole must be flame proofed (resistant). In doing this, the hole in the scenery and wiring device allows for splicing means and strain relief of the feeding wiring. The problem with this method is that unless the box has a strap to mount it to the scenery, the two #8 screws used to mount keyless lamp holder to electrical box are a insufficient means of mounting it. It is also awkward in needing someone to hold the rear of the box while another person screws in the lamp holder. Should it break or a screw come loose, both could fall or become of hazzard. Your electrical box must have a strap to mount it. It also must be grounded unless plastic type. These are added expenses.

While done, none above are proper or use of the lamp bases as intended.



My or other choices in lamp base type and wiring system:

www.cooperwiringdevices.com go to the Catalog under the category of Lampholder. Choose Sign and Scoreboard Lighting.
There are various type of lamp holder listed that are designed for this application listed. Some such as the #732 are pendant type are not for this application but between the #734 and 4734-2 there is a variety of excellent mounting means and style available designed for this surface mount wire from the rear sign use.
In addition to having a permanent secure means of mount, they are knob and tube style in parallel conductors feeding thru and not needing any splicing or pig tails to attach them. Instead, you use stranded building wire running right thru the lamp base such as MTW (recommended) and there is like on a Add A Tap, insulation piercing prongs that make contact with the wire in an enclosed area. Add A Tap is more a term for something that’s insulation piercing as means of connection than a specific type of wiring device such as a plug. Very fast and easy to connect without any special electrical skills required. White wire to silver prong, black, blue or red to gold prong dependant upon the circuit. Twist the cap and it in enclosing the junction that’s now safe, it also pierces the wire’s insulation to make contact. It is advisable to use a larger gauge of wire on something like this. 12AWG wire will better fit within the cap and there will be less damage to the conductor by the insulation piercing prong that could damage a smaller conductor. I highly recommend this type of wiring device. You can get them by way of electrical supplier or sign supply company such as Denver Sign Supply http://www.denversignsupply.com/ . The lamp bases are very inexpensive also. This especially since you do not in addition to lamp base need any wire nuts or junction boxes.

I mention knob and tube type wiring above because this style of wiring is in how you do it. Two or more parallel spaced conductors as if railroad tracks that are in the open to the air without outer jacket and supported when they run thru framing. They must have some form of bushing and support so they are not in direct contact with building material they run thru. Keep them neat parallel and supported and it’s very fast and effective as a means.

An alternative to this above type of lamp base is either the Leviton http://www.leviton.com/ #9063 or 19062 2x2 square surface mounting science experiment type lamp base that has exposed contacts. Or better yet the porcelain two piece #9880 and 9882 which has a porcelain screw in cover to protect the terminals from contact. This type can also be surface mounted which would mean you either have your wiring - pigtails off the main conductor line exposed or coming thru a bushed hole next to the lamp base. This bushed hole would be best to be a rubberized one such as McMaster www.mcmaster.com #9600k54 rubber grommet. Insert the grommet into the hole and your wire in feeding thru it has little to no chance of rubbing a sharp surface. While on line, also have a look at #7063k34 for a means of tap splicing that is safe and simple to use in the open without necessitating a bunch of wire nuts and junction boxes. Wire nuts are not at all recommended for something such as this.
An alternate method for use of the #9880 above is to mount it’s screw on cover directly thru a hole in the sign’s surface so the wiring part of the device is on the rear of the sign. The cover than is the means of holding the lamp base to the surface. This method while done and given a insulation washer between screw terminal and sign surface is for the most part safe, but probably not the best to do without guidance in doing so. 1/4" material for the sign’s face might be a little thick for means of mounting and metal coverings should not come into direct contact with the neutral screw base of the lamp holder. This is a traditional way of doing a sign but needs supervision in doing so.

A third class of lamp base that would work well is the snap in or pigtailed lamp holders from page L-8 of the D-502 catalog. There is a combination of the above Eagle type of lamp holder with spring clips to retain the lamp base in a drilled hole Leviton #8880 & 8875, but in this case with screw terminals necessitating pigtails to attach the lamp base to fixture to fixture wiring, and other types similar to the #9880 that use a two piece lamp base - it’s top cover as means of mounting. This already has pigtails coming off it or is available with screw terminals. These two piece such as the #10045, 10065, 20070 and 10085. All will work fine as long as the shell of the neutral does not come into contact with metal. The #9885, 9350, 8871 are also suitable. A good electrical supply should have a few of these types in stock if not at least be able to get them easily. Some will be OEM or necessary to buy in bulk. If that’s the case, going to a sign supply that does buy in bulk would be a solution for buying individual bases.

Note that this third type of lamp base has something in common with the second example - both are what’s called pig-tail attachment type. In other words, instead of your conductors running directly thru the lamp base, there is a necessity for a separate conductor to splice into the circuit. The above insulation piercing splice - your home depot would stock is a suitable way of doing this. Remember that such a tap is only to be used on stranded wire. I am not recommending the use of solid core building wire or wire nuts because the use of either will require junction boxes at each splicing point or at very least proper support of each junction and the rear of the sign to be enclosed with flame resistant material. Wire nuts fall off, and if not properly applied allow conductors to work loose or get cut by them. All splicing needs supervision but the wire nut needs much more work and training.




A statement of intent on my part:

The recommendations posted so far are only home owner grade (Home Depot) solutions to the fixture mounting problem - and all are not really designed for your purpose. None in being designed for your application would fit within the spirit of the NEC given other solutions easily available I post about that would better fit your intent. In building this sign and must comply with the code, just as you don’t use home owner grade plugs on stage, you should be using the proper and designed for your application lamp bases and follow good practice on how it’s wired. Stop shopping at Home Depot for specific electrical needs when you need to compromise your intent. Compromise just because your home supplier does not carry in stock something is a compromise in your design and more important safety. Never accept this. If you are doing something such as a chase effect on a sign this is specifically covered by the NEC. You should comply with the materials and standards of practice in doing so. Just because Home Depot does not carry what you need does not mean that you don’t need to comply with the intent and safety rational of the code.

You made a design choice to do a sign based type of chase effect mounted to scenery, now that you have made it, choice of what safety guidelines or intent you follow is as an adult and professional in charged of the project not your choice in deciding what way because it’s not commonly available you will follow in building anyway. Hack work in doing the best you can given limited materials your home center carries is against, “a professional workmen like manner” rule one of the NEC for all work to be done. No you can’t just use some form of stringer or clip light based add a tap system, in that it does not provide a solid means of mounting designed for this purpose. Something about “professional workmen like way” as primary over specific clause intent of the code in what you do. Using lamp bases that only “can be made to work” but are not designed for this application is hack workmenship.

All above lamp base types assume as probably the intent that wiring is done behind the face of the scenery. There is still not known what extent of lamp base is to be mounted to the face of the scenery verses the intent of only lamps showing. Given a 4" keyless porcelain or plastic lamp base bought - with or without the at least minimum ½" boxes behind it as thought of, we assume that lamp bases showing behind the lamps is not a problem but can probably assume the wire is not intended to be exposed on the surface. This as opposed to just lamps popping thru the scenery as possible with other types of lamp base. Nor is it known what is behind the scenery wire way now that might have to have a rear panel protecting it. Dependant upon type of splice and lamp base, if there is exposed lamp base contacts or connections you will need to enclose the rear of this wiring device and flame treat all surfaces. Moving scenery or especially on the legs, people coming into close contact with the wiring must be protected against accidental contact.

Have I mentioned that while this is a very good project to learn from and something all stage tech electricians will deal with, you need experienced supervision. Once built a sign for the “A-Teens” (what ever they are or were) tour which used a similar type of chase effect by way of lamp bases mounted to in this case ½" MDO plywood cut out letters. Had help in building it due to time constraints. An hour before load out for the tour it seemed there was problems. Something about phantom lamps, non-working lamps and a circuit at half wattage when at full over two channels. Major problems of wiring in series or otherwise that was due to a lack of supervision on my part of what was done by those doing to the sign the extent they understood wiring and my instruction. Had I instructed better or supervised better, there will not have been a problem in wiring of the also three circuit chasing sign. Nothing blew up, but the potential for hazzard was there. If you are not ME and in by way of real ME status - not just the best person available for the production that’s able to hook up the plot, seek help in this other than normal project. Those which are sufficient to follow a plot in plugging in fixture 119 to circuit 24, nor those with training to re-wire a Fresnel, does not mean training in this different form of wiring. Person to do a project by default only available is bad practice. Just as you don’t re-wire your dimmer packs, wiring a sign is no less important to be trained in doing. It’s easy enough but there is tricks only experience will make known.

Self ego should have no bearing upon things built as a professional. If you don’t fully grasp all the application tasked with, get help - not just on line, unless it is sufficient in guidance but on site. Should a designer or director propose such things you don’t have experience with as a master, bring it up early that it’s possible to but not within your training so that budget in getting help or alternative plans can be found earlier rather than having to budget time and money for them later. When doing thing not trained in, ensure the safe use of the gear by those other than you should be a pre-production problem rather than something that you said you can do and does not turn out to be the case.

So you hire a licenced electrician for a piece of scenery to supervise, or have to at very least consult the head of electrics at the school in your doing some special piece of equipment. If nothing else, do a mock up and ask if this is safe well before you attempt to do so. In the end, as a professional, you don’t mess with what you are not qualified to do, nor have proper supervision and training in doing. “I can do this”, is a recipe for problems when no training or background in it. When it fails as sometimes hopeful if caught before it becomes a hazzard you learn. Otherwise, should this proscenium catch on fire due to something you did not suspect, what are you to say - “sorry” in having had the title of ME but not really been sufficient for it’s needs other than thinking it opportunity over base of knowledge and experience? Even as a TD, do you really know all you should or are you simply without oversight the one that can do the simple parts of the job? Have you done the cable/amperage calculations yourself in something you are absolutely sure of, do you know on a piece of zip cord which is intended to be the neutral? Or has ego and those forcing you into such a un-supervised position forced you into being the person in need for what you are not trained sufficiently for? Hire someone qualified for this project to supervise.