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.