Wiring Extension Cables

[jaamulberry]

We had some new guys wire some extension cables at our school and they wired the black and white in reverse on both sides. How big of a problem is this? We have checked most of the cable but we think a few are already in use. Does it matter since both are wrong? What would happen if one side was wrong but the other side was right.

Thanks,

JAAM

 

[MNicolai]

Mechanically, your cables will function if two conductors are switched, consistently, at both ends --but you should still remove them from use immediately until they have been checked through.

If someone services the end of a cable, which is a fairly routine procedure, they may not realize the wires are flipped, and may correctly reterminate the wires on one end of the cable. Upon doing so, the neutral of the connecting device will now be energized to 120v. Very dangerous, and a very efficient way of damaging or destroying the connected device.

 

[theatricalmatt]

The fact that you've noticed they're wired incorrectly is enough. If they haven't wired the cables correctly, who knows what other problems might exist?

The proper thing to do is to take them out of circulation, tag them, and then have an afternoon or day of repairing them. Are the "new guys" students? Overhire? See if you can get them involved to properly train them.

Reversing the hot and the neutral (the black and white wires) causes a number of problems, typically with switches and dimmers. One potential problem would be switching off the neutral rather than the hot, which would result in having 240vac rather than a dead circuit.

 

[jaamulberry]

I kinda figured :/. We had an enormous amount of cables that needed to be checked/rewired and they wanted to help so they came up and rewired stuff. If it didn't they were instructed to fix both ends just in case one end might be a little loose. While one the subject I have two more questions if you will. Why one plugs is it labeled "W Y X" do they have any special meaning or is it just Y is Black/Hot, W is Ground, and X is White/Netural.

My second question is how do you clean dusty/sticky cable from old gaff or e tape. Do you just let it go or is there a good way to get rid of such things. I hear goo gone will eat through the cable eventually.

 

[theatricalmatt]

Check the exact type of plug. A 120vac plug needs three conductors - a hot, a neutral, and a ground. But a plug used for 240vac takes two hots, no neutral, and a ground.

The labelling inside the plug is meant to signify what to connect to what. I'm familiar with seeing X, Y, and Z signify each of three phases. But check the manufacturer's documentation.

NEMA (the National Electric Manufacturer's Association) has a great listing of what plugs are used for which purpose, and how they're wired. Not all connectors are NEMA listed, though.

As far as cleaning old cable - no good way other than replacing it, and being more proactive about removing unneeded gaff tape labels at strike in the future.

 

[MNicolai]

Generally W is white (neutral), and X/Y/Z refer to phases of three-phase power, and G would be used for ground. Not sure what you're wiring but you'd best double check your wiring configuration is supposed to be what you think it is.

 

[jaamulberry]

Have I been doing it wrong :| Attached are what I use for reference. Is this incorrect? Did they do it right by mistake? :/

 

[coldnorth57]

hmmmmm

these are the normal 120v 20a twist locks

 

[derekleffew]

... My second question is how do you clean dusty/sticky cable from old gaff or e tape. Do you just let it go or is there a good way to get rid of such things. I hear goo gone will eat through the cable eventually.

http://www.controlbooth.com/threads/cleaning-cables.32355
http://www.controlbooth.com/threads/removing-that-mean-icky-gaffa-goo-left-on-cables.1040/

 

[Lextech]

Non-Nema 2 is a old connector that I saw alot of in my early days in the north east US. If you look it says 125/250volt and I saw it used for 120volt 20 amp all the time. We were told pin points to hot, meaning the ground nub. I don't know what the Official standard is however. That being said, if you are using them for 120 volt, hot, neutral and ground operation and ALL of you cables and units and anything else you plug into in your spaces are wired all the same you should be okay. Also the ones I remember were all Pass And Seymour and you should be able to check with them as to how were originally meant to be used, I want to say it was something like a 4 digit part number that started with 48. I know they were still listed in the P&S catalog in the mid 2000s. If you PM me on Monday I have a P&S book at my office and I can see if it is still listed.

 

[SteveB]

I still have a theater using this c- - p, X is hot, Y is neutral. I only know this as some of my connectors use the X/Y code, older have brass, copper. Thus it's easy to figure out.

I'm uncertain if they are legal for 120v, single phase use at this point.


Sent from my iPad using Tapatalk

 

[Dionysus]

The fact that you've noticed they're wired incorrectly is enough. If they haven't wired the cables correctly, who knows what other problems might exist?

The proper thing to do is to take them out of circulation, tag them, and then have an afternoon or day of repairing them. Are the "new guys" students? Overhire? See if you can get them involved to properly train them.

Reversing the hot and the neutral (the black and white wires) causes a number of problems, typically with switches and dimmers. One potential problem would be switching off the neutral rather than the hot, which would result in having 240vac rather than a dead circuit.

You can't magically make 240v from a 120v circuit. Switching a "Neutral" (in this case actually not neutral, actually 'identified') does not create 240v, but does leave 120v still potentially present at the device, all the way to the switch. This is not safe at all.

Those Non-NEMA connectors shown in the image "non nema 2" are indeed a 240v connector that is why they are labeled that way. They not not intended for 120v, none the less they have been used for 120v as previously mentioned. As long as its all the same it will work fine. Any 120v twist lock will have three different pin shape/sizes (like non nema image), you'll notice that two of the pins on that connector look the same, that is because they are both intended to be 'hot' for 240v.

I'd say its best if at some time to make sure 120v designed connectors are used on 120v, 240 on 240. This way noone may be "stupid" at connect something of the wrong voltage.

About cables being wired backwards. Generally if they wired them backwards, they obviously don't know what they are doing and the cables should be all checked. Generally if they wired them backwards you'll also see things like WAY too much of the jacket stripped off (thus lots of wire stuffed into the connector), strain reliefs incorrectly installed, insulation inside the connection, too much of the wire stripped and about to short out, etc, etc. You can't just toss people a cable, plug end, and tools and say "have at it". Making cables is much more invovled than some may think. Most people have never made a cable in their lives. HOW MANY CABLES EVEN IN PRO OR SEMI PRO THEATRES HAVE I SEEN MADE WRONG?! The answer is too many for my own comfort. The second I see a suspect cable in the field I look at it, and if it fails my inspection even in some small way I cut the ends off or repair it.

 

[STEVETERRY]

We had some new guys wire some extension cables at our school and they wired the black and white in reverse on both sides. How big of a problem is this? We have checked most of the cable but we think a few are already in use. Does it matter since both are wrong? What would happen if one side was wrong but the other side was right.

Thanks,

JAAM

Fix the color coding issue--it will prevent safety problems in the future.

ST

 

[coldnorth57]

We had some new guys wire some extension cables at our school and they wired the black and white in reverse on both sides. How big of a problem is this? We have checked most of the cable but we think a few are already in use. Does it matter since both are wrong? What would happen if one side was wrong but the other side was right.

Thanks,

JAAM

just like to say one thing, at what type of school lets you puts ends on cords .... I am the theatre technician at a high school and the union wont let me or the students even put xlr ends on

 

[derekleffew]

Fix the color coding issue--it will prevent safety problems in the future.

ST

Ah, but therein lies the rub. Posts 7 & 11 are contradictory--which one is correct?

Given a 125/250 non-NEMA plug (aka TLGO ) used for 120V,
a) green wire to W, black wire to X, white wire to Y
OR
b) green wire to W, white wire to X, black wire to Y
?

Given the confusion here, seems totally conceivable that this could cause issues in the venue.

 

[jaamulberry]

just like to say one thing, at what type of school lets you puts ends on cords .... I am the theatre technician at a high school and the union wont let me or the students even put xlr ends on

We had a massive amount of cable and and not enough work. Enter untrained students doing this. We have looked at all the cables touched and fixed them. Now I am confused about what we should do for cabling the right way.

Ah, but therein lies the rub. Posts 7 & 11 are contradictory--which one is correct?

Given a 125/250 non-NEMA plug (aka TLGO ) used for 120V,
a) green wire to W, black wire to X, white wire to Y
OR
b) green wire to W, white wire to X, black wire to Y
?

Given the confusion here, seems totally conceivable that this could cause issues in the venue.

Which one is right? Does it depend on our building? I know its out of date but we don't have the money to replace every receptacle and or pay the electricians to do it. I am one of the few students allowed to do it only because I have a high interest and realize the risk involved. Am I opening a can of worms I shouldn't have?

 

[theatricalmatt]

So, you've met the boundary between physics and best practices. To wit, electrons don't care what color insulation is on the conductor -- they can't see, because it's too dark in there -- but they will follow the easiest path. Your power situation is going to run best is all the cables are wired the same; in fact, things may fail in very unsafe ways if they're not wired uniformly.

I'm pretty certain that, with the non-NEMA twistlocks, the 'pin' on the ground is meant to point to the hot. But, to be more certain, you could de-energize any of the leads coming off the dimmer rack (perhaps a multicable head, a patch panel, or an electric raceway) and double-check. Honestly, I would go with how your facility is wired; but make it consistent, and then make certain to note it in very large print at the appropriate locations -- the dimmer rack, extension cord rack, and lighting manual. Then, begin looking at all of the extension cords, connectors on lighting instruments, and any other location where a student may have wired it, or could conceivable have to engineer a field repair.

So long as you make certain to document what you've checked, and corrected any mistakes you find, you'll get through it. It'll take time, but you'll get through it.

 

[JD]

Technically, all 120 volt appliances, 2 or 3 pin (HN, HNG) must be able to be operated safely even if the hot and neutral are reversed. At no point should the neutral come in contact with the case. Appliance designers take extra steps with regard to the "assumed" hot. For example, on a standard table lamp with a two wire cord, the presumed hot is routed through the switch, where as the neutral is connected to the shell of the socket, where human contact is more likely if the lamp is removed. The two wire cable is indexed with a ridge along one of the two conductors, and the two prong plug has a larger blade to index the neutral pin of the receptacle.
That being said, here is why all the cable connectors the OP has should be inspected:
1) As said before, if the cable is cut in length and additional connectors are installed correctly, the neutral index will be hot, thus removing a layer of mandatory safety.
2) If something as simple as the colors are wrong, what other termination mistakes were made? Poor termination can cause the connector to pull off at a much lower stress level than would be expected. Poor compression on the connection can cause a hot-spot or fire. Stray strands can cause a short.
3) Self made cables do not carry any type of certification and may not be allowed on some stages unless constructed by someone who carries the proper certification. Therefore, if there is a problem, they will be the first suspect.

 

[jaamulberry]

Thanks everyone for your help with this matter. I know electricity is one of those things that is risky and hard to teach/give advice over a screen.

 

[JChenault]

Thanks everyone for your help with this matter. I know electricity is one of those things that is risky and hard to teach/give advice over a screen.

I'm sorry, you just hit a hot button of mine.

Electricity is nit risky. It is well understood if you read and study, and the kinds of stuff we do as theatre electricians is pretty basic. You need to pay attention, but it is not especially hard or risky with some effort.

Driving a car is risky. Flying an airplane is risky. Working on a ladder is risky. Petting a stray dog is risky. Electricity may seem risky to the uninitiated, but it is really pretty comprehensible and easy with the appropriate effort,

Phew. Time to get off of the soapbox now and go hang some lights.