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Are 14AWG two-fers standard?

Discussion in 'Lighting and Electrics' started by Charc, Feb 20, 2008.

  1. Charc

    Charc Well-Known Member

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    So I noticed I had 4 x 500W-PAR56-MFL circuited on a 14AWG two-fer. This has me uneasy, so I removed the two-fer this afternoon. Especially because that breaker keeps tripping. Really one of my biggest concerns is having anything (except for instrument whips) be anything but 12AWG, considering we have all 20A dimmers. Too often are two-fers used as 2' jumpers.

    Anyways, I'm wondering if these are a standard. The craftsmanship on these two-fers far surpasses anything I've seen at my theatre before, so I think they were professionally wired. (Some sort of locking washer on the set screws, crimp terminals actually crimped on, working strain relief made out of something I'm not familiar with [friction tape?], plus these look relatively new, no pitting on pins, no gaff-goo)

    Thoughts here, guys?

    Edit: AND gals, I'm not from the 1900's! :oops:
     
  2. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    We've had this discussion before, here, read previous and subsequent posts also. IIRC, under NEC Art. 520, 12/3 SJO is permitted provided neither leg exceeds 36". No variant of 14/3 is permitted. In theory it would be difficult to overload one leg of a 14AWG tufer, that, and it's easier to fit 14/3 SO/SJO into the strain-relief of the pin connector, but the answer to your original question is a big red NO!
     
  3. JD

    JD Well-Known Member

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    There are plenty of products on the market that don't meet code. Your instinct is correct.

    It is actually the second part of your post that kicks in my pet peeve. How can a dimmer manufacturer build a 2k dimmer (ok, 2.4 is usually the rating) that doesn't handle a 2k load? I have seen SO many over the years! I used to always rent equipment before I bought it to weed this out. (Back in the "old" days.) The problem of course is cold inrush. Many magnetic breakers and some thermal (Square D comes to mind) will trip on the turn on. The best combos I remember were those dimmers that used a slower 20 amp breaker, but then a faster internal silver sand fuse (usually 35 amp for a 2.4k) to handle protection. I believe TTI was the one doing that. Never had a false trip with those. EDIs had some trip problems, but were not too bad. I did not like the scrimmeretts, which had a 1.2k rating, but had a 20 amp fuse. Although all connections were better than 20 amps in ratings, I just thought it was bad to fuse 1.2k at 20 amps, especially from a respected manufacturer displaying a UL approval stamp.

    I guess I figured that over the last 20 to 30 years this problem was behind us all. It raises old rage to hear that some are having to still deal with it.
     
  4. Charc

    Charc Well-Known Member

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    Per the "had this discussion before", I don't believe we have, as it was specific to 14/3.

    That's the answer I was looking for. These two-fers will remain in service, but I'll flag 'em. I still wonder how a company could be selling these though.

    EditL Moved the following sentence down, and added more, typed before JD posted: (I don't think this explains the breaker though... ****.)

    Inrush, that's interesting. These are on the architectural system, and have a default up-fade of (I think) 3 seconds. So is overloading the dimmer really the issue?
     
  5. ship

    ship Senior Team Emeritus Premium Member

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    The description limits the twofer to one of a few styles that use ring terminals inside them.


    Standard no, Given a stage pin plug/slip plug that’s rated for 20A (leaving the debate about molded adaptors aside for the moment) if the plug is rated for 20A, the cable powered from it needs to also be rated for 20A.

    Assuming a 12-10ga ring terminal, two 12ga wires added together equal nine gauge thus would not fit into the ring terminal thus someone’s bright idea of using a smaller gauge of wire when once added together equal 11ga which would fit into the above ring terminal. (General rule adding two stranded wires together equals three sizes larger thus 16ga + 16ga = 13ga.)

    Not so sure what you mean about “working strain relief”very few and none of the plugs with ring terminals have dual wire designed holes or strain reliefs for the dual wire including those designed for asbestos wire with three separate holes for the wire to get out of the plug. Friction tape is old school and good stuff, (I use it a lot) not a problem with that as the best thing to be using in such a situation of bulking up a strain relief unless directly at the rear of a lighting fixture where heat could cause flame up of the tar in the tape.

    Overall if you have 2,000 Watts feeding thru 14ga wire that is rated for 1,800 Watts, that is a bad thing and could cause tripping of a breaker due to voltage drop. Your cable and plug should also be getting really warm. On the other hand, assuming the load is balanced between each of the wires, the cable than with 1,000 Watts load is rated for what you are applying to it. (Not the best idea... but safe.) Given no heat damage to the ring terminals (external tooth lock washers are standard practice), it does not explain how or why your breakers are tripping. Could be something else in the system. Could also be too many connections, assuming three 14ga twofers now feeding the four fixtures, possible this many twofers with the gauge of wire is the cause. Possible but not likely in my opinion.

    Still I would scrap the 14ga twofers, they at best are a weak link needing supervision that is not sufficiently there for their safe use.

     
  6. ship

    ship Senior Team Emeritus Premium Member

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    Given its an architectural system, 2Kw worth of lamps given voltage drop could potentially trip a breaker when brought up fast without warming. Your 3sec. should be sufficient however but given various connections, long run lengths, screw terminal connections etc. etc. etc. it is possible that the amperage is higher than 20A at the breaker. Should have an electrician check that out and otherwise if a breaker frequently trips, it might be time to replace it in it's trip ratio wearing down some.
     
  7. Charc

    Charc Well-Known Member

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    Thanks Ship, I'll note it for if I can ever get the in-house electrician in.
     
  8. JD

    JD Well-Known Member

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    You might also just have a fussy breaker! These things are not magic, they have a range to their tolerance, and sometime shift way out of range after a few years.

    Thermal breakers also can trip due to heat caused by oxidation of the contacts inside them. A three second fade up rules out inrush. I have autopsied many old circuit breakers, and believe me, it leaves you with an insecure feeling after seeing what's inside them! Remember Federal Pacific? Many places burned down due to the fact that their breakers had a habit of jamming in the on position, quite literally allowing the full pole current to travel to the load. (If you don't remember, just google the words: federal pacific fire) Most times, luckily, breakers are likely to false trip at a low load.
     
  9. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    I'd never heard of that company until recently, while watching the HGTV show: House Detective, on TiVo, of course.:)
     
  10. ship

    ship Senior Team Emeritus Premium Member

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    I can personally tell you of such an experience when doing something stupid, in having to with great effort release the conduit and copper now melting into my palms while the stage lights in another room brown out all about breakers not tripping.... Not fun.

    Back to the concept of the 14ga twofer... I remember sufficiently this being a taught technique at one point - don't remember if passed on technique or book learned. As stated, safe enough for most applications when supervised of a splitted load equalling less than 2.4Kw or in this case 2,000 Watts which is where this thing came from. By todays standards in having learned better, such a twofer does not sufficiently idiot proof the system as is the case in most systems having problems and what current standards reflect. The 14ga twofer assumes one is not say putting anything over 1,800 Watts such as 2Kw on one leg and even nothing to up to 600w on the other circuit in the breaker (assuming it is in good condition) safely handling the load. On the other hand the wire feeding the twofer in not being able to handle the current would be the weak link and might or might not even cause the breaker to trip before having a situation like what is presented in the Q' of the Day with the panel mount that melted down. Possibly in that case also a bad circuit breaker to look at in addition to what the problem at the panel mount is.

    None the less, one could say put 2Kw on one leg of a twofer, and 400w on the other leg of it and not expect a breaker to trip. Given that, the cable would melt down without any protection. Thus the concept of very supervised use or better yet removing from your inventory.

    Is it possible that three of the above four lamps were tapped off one leg of the twofer? You note the twofer(s) are in excellent condition that leads one to believe this is not the case, but on the other hand given voltage drop and longer twofers, weaker connections in the system and smaller gauge wire in use, such a thing could add up to a circuit breaker tripping also - as a theory. One leg at 1,500w, smaller gauge cable, loose connections (any number of reasons) and long cable and even conduit runs. That means voltage drop and while it should be appairent at the twofer, if the breaker really is good it could mean the breaker is doing its job before something in the system melted down.

    This much less the concept of hot patching - plugging lamps into live circuits could defeat the warm up/high inrush current dismissal.

    Lots of things, and something for someone highly trained and on site to reproduce and check out in finding the cause before there is other problems.

     

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