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Author Topic: 30A to 15A Pigtails?  (Read 6142 times)

Kevin Graf

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Re: 30A to 15A Pigtails?
« Reply #10 on: February 07, 2014, 02:30:04 pm »

[.....................................]

I believe the NEC does permit parallel conductors on one phase/leg (i.e., to achieve 30A service you can parallel two 14 AWG wires rated at 15A each; though it's usually used where larger size of wires are impractical to work with such as in 400A service) but there are specific methods of installation required.

Only large wires can be paralleled. I believe it's 6AWG and bigger.  This is a case of the NEC anticipating that smaller wires might be separated and re-purposed  without resizing the breaker.
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Lyle Williams

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Re: 30A to 15A Pigtails?
« Reply #11 on: February 07, 2014, 02:59:13 pm »

While there are circumstances (that a layman has no way of being sure of) where the y-cable cheater may work, it is highly dangerous and illegal.  You are not allowed to try and kill people so your show can be 3dB louder.

If one of these was ever seen at a site (even not in service) everything would be shut down on the spot and reported to the OH&S regulator. 

Even once the regulator was done with you, you would never work in sound again.  Seriously, this is such a big screw up that the word would get around everywhere.  All you would be known for would be that y-cable.
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TJ (Tom) Cornish

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Re: 30A to 15A Pigtails?
« Reply #12 on: February 07, 2014, 04:02:12 pm »

One thing to note is that for the aforementioned cheater to provide 30A 120V from two 15A 120V circuits, both circuits MUST be on the same phase and leg of the electrical service.

Another problem with the cheater is that there is nearly 100% certainty that the wiring of the two circuits is different length and therefore different resistances. This means that more current will flow over the circuit with lower resistance; you will likely not get a full 30A before one of the breakers trips (then the other will trip immediately due to overload).

I believe the NEC does permit parallel conductors on one phase/leg (i.e., to achieve 30A service you can parallel two 14 AWG wires rated at 15A each; though it's usually used where larger size of wires are impractical to work with such as in 400A service) but there are specific methods of installation required.
While not defending the practice, I took the OP to mean that one 15A circuit would feed each leg of the 14-30, in which case it wouldn't make any difference which phase(s) the supply was from.
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Mike Sokol

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Re: 30A to 15A Pigtails?
« Reply #13 on: February 07, 2014, 04:40:44 pm »

I believe the NEC does permit parallel conductors on one phase/leg (i.e., to achieve 30A service you can parallel two 14 AWG wires rated at 15A each; though it's usually used where larger size of wires are impractical to work with such as in 400A service) but there are specific methods of installation required.

Yeah, but NEVER with extension cords...  ::)
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Jonathan Johnson

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Re: 30A to 15A Pigtails?
« Reply #14 on: February 07, 2014, 06:40:58 pm »

One thing to note is that for the aforementioned cheater to provide 30A 120V from two 15A 120V circuits, both circuits MUST be on the same phase and leg of the electrical service.

While not defending the practice, I took the OP to mean that one 15A circuit would feed each leg of the 14-30, in which case it wouldn't make any difference which phase(s) the supply was from.

I didn't mean to make it sound like I was condoning the practice in a "well, if you did it THIS way it'll be OK" type of manner. Any kind of dual-source cheater is dangerous and should never be considered acceptable practice. Proper tie-ins are proper.

I see now that I was misunderstanding the OP. I made the assumption that the connection was only 120V 30A; the L14-30 connection is in fact rated for 125/250V 30A. Connected properly, it would provide for up to 60A of 120V loads.

From a theoretical standpoint, if each leg of the proposed "cheater" was going to one leg each of the L14-30, phasing doesn't necessarily matter IF there are no double-pole (240V) loads. However, the connection will be limited to 15A 120V on each leg, not 30A. Therefore, the total load could not exceed 30A of 120V loads (or the sum of the capacity of the two 120V circuits). And as Mike pointed out, you could have an overcurrent situation on one of the neutrals for which there is no protection.

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N.B. -- In the United States, electrical wiring devices are typically rated at 125V or 250V nominal (or a combination thereof). However, the typical single-phase voltage distribution is 120V and 240V (with 208V and 277V variations with 3-phase wiring). Historically it was somewhat lower, so you may see mention from time to time of 110V or 220V. Practically speaking, any mention of voltage between 110V and 125V (or 220V and 250V) is considered to be within the same AC voltage spec. Utility delivery voltage is considered to be acceptable anywhere within that range; less than 110V is considered undervoltage while over 125V is considered overvoltage.
« Last Edit: February 07, 2014, 06:43:16 pm by Jonathan Johnson »
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Stephen Swaffer

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Re: 30A to 15A Pigtails?
« Reply #15 on: February 07, 2014, 11:40:35 pm »

Actually, you might be able to do it with extension cords as the NEC does allow cables to be paralled; however the minimum size conductor is 1/0  (NEC 2013 310.10 (h) (1)-and finding extension cords that big might be more of a problem than just finding the right tie in.  There are cases where smaller wires can be paralled, but there are severe restrictions-essentially you cannot increase ampacity with smaller wires paralled-it appears to me that it is only allowed to for purposes of reducing voltage drop.
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Steve Swaffer

Jonathan Johnson

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Re: 30A to 15A Pigtails?
« Reply #16 on: February 08, 2014, 01:23:02 am »

Actually, you might be able to do it with extension cords as the NEC does allow cables to be paralled; however the minimum size conductor is 1/0  (NEC 2013 310.10 (h) (1)-and finding extension cords that big might be more of a problem than just finding the right tie in.

Probably not, though. I believe that disconnects must interrupt both conductors simultaneously (though code might not even permit parallel disconnects) and since a plug and receptacle is considered a disconnect, there's no way to ensure that two extension cords are unplugged simultaneously.
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Tim McCulloch

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Re: 30A to 15A Pigtails?
« Reply #17 on: February 08, 2014, 10:29:49 am »

Probably not, though. I believe that disconnects must interrupt both ALL line conductors simultaneously (though code might not even permit parallel disconnects) and since a plug and receptacle is considered a disconnect, there's no way to ensure that two extension cords are unplugged simultaneously.

You're on the right track.  I fixed it for you.
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Andrew Brubaker

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Re: 30A to 15A Pigtails?
« Reply #18 on: February 12, 2014, 10:09:40 pm »

I see now that I was misunderstanding the OP. I made the assumption that the connection was only 120V 30A; the L14-30 connection is in fact rated for 125/250V 30A. Connected properly, it would provide for up to 60A of 120V loads.

From a theoretical standpoint, if each leg of the proposed "cheater" was going to one leg each of the L14-30, phasing doesn't necessarily matter IF there are no double-pole (240V) loads. However, the connection will be limited to 15A 120V on each leg, not 30A. Therefore, the total load could not exceed 30A of 120V loads (or the sum of the capacity of the two 120V circuits). And as Mike pointed out, you could have an overcurrent situation on one of the neutrals for which there is no protection.

Yes, that's what I was asking about. And I realize it would not be the full 60A but only 30A. But I'm just going to stick with Edison extension cords when I can't wire in a distro directly. That's what I've done in the past anyways. I was just curious and wanted to get everyone's thoughts if it was possible. And NO was obviously the answer
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ProSoundWeb Community

Re: 30A to 15A Pigtails?
« Reply #18 on: February 12, 2014, 10:09:40 pm »


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