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Author Topic: Voltage sag solution?  (Read 1915 times)

David Allred

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Re: Voltage sag solution?
« Reply #10 on: March 14, 2017, 01:12:10 pm »

Thank you Eric & Jonathan for adding safe alternate solutions.
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TJ (Tom) Cornish

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Re: Voltage sag solution?
« Reply #11 on: March 14, 2017, 01:18:53 pm »

Please explain #1.
Running parallel conductors - wire with the same termination point on both ends- (or a parallel set of 3 conductors in your example) is not allowed other than in very high-current situations (several hundred amps), and is definitely not allowable with two extension cords.

10 demerits to you for using #16 extension cords; 5 more if they're orange.

The best you can do with your current equipment is to divide the load between your two cords, as mentioned, but even that's putting lipstick on a pig.  175' is too long of a run even with real #12 cords - you need a generator.

NEC reference for parallel conductors:  NEC 310.10(H)(1) Conductors in parallel, General "Aluminum, copper-clad aluminum, or copper conductors, for each phase, polarity, neutral, or grounded circuit shall be permitted to be connected in parallel (electrically joined at both ends) only in sizes 1/0AWG and larger where installed in accordance with 310.10(H)(2) through (H)(6)."
« Last Edit: March 14, 2017, 01:26:00 pm by TJ (Tom) Cornish »
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Tim McCulloch

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Re: Voltage sag solution?
« Reply #12 on: March 14, 2017, 02:30:11 pm »

Running parallel conductors - wire with the same termination point on both ends- (or a parallel set of 3 conductors in your example) is not allowed other than in very high-current situations (several hundred amps), and is definitely not allowable with two extension cords.

10 demerits to you for using #16 extension cords; 5 more if they're orange.

The best you can do with your current equipment is to divide the load between your two cords, as mentioned, but even that's putting lipstick on a pig.  175' is too long of a run even with real #12 cords - you need a generator.

NEC reference for parallel conductors:  NEC 310.10(H)(1) Conductors in parallel, General "Aluminum, copper-clad aluminum, or copper conductors, for each phase, polarity, neutral, or grounded circuit shall be permitted to be connected in parallel (electrically joined at both ends) only in sizes 1/0AWG and larger where installed in accordance with 310.10(H)(2) through (H)(6)."

If this is being used as a "feeder" to anything that could be construed as as "switchboard" it also fails in 520 where minimum feeder sizing and parallel conductors are addressed.

David, just buy or build cords with larger conductors.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Mike Sokol

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Re: Voltage sag solution?
« Reply #13 on: March 14, 2017, 03:04:50 pm »

Please explain #1.

OK everyone... Let's not beat up on someone who's trying to learn safety.

Code only allows parallel wiring when they're single conductors (not bundled extension cords) and with large diameter single conductor over 1/0 that would be too cumbersome if a single larger conductor was used. See here for a pretty good explanation of when it's allowed: http://www.ecmag.com/section/systems/conductors-connected-parallel

Remember the NEC is a century long document created by a lot of engineers who want to prevent loss of life and equipment. While you "might" be able to get away with your wiring scenario and have nothing bad happen, if someone less knowledgeable were to do something silly (like use different length extension cords or plug into different phases, etc...) it could become very dangerous and possibly cause a fire, damaged equipment or even loss of life. Plus you have to consider your own liability. If you were to do something like this and a fire or death occur, then you would be on the hook for potentially millions of dollars. I assume you don't have a business and insurance, so they would come for your house, properties, car, boat, etc... It's just not worth the risk to save a few bucks. As others have noted, a heavier extension cord will reduce the voltage drop considerably. And many times I'll run a long 10 gauge extension cord 100 feet just to reduce the voltage drop, even on a 15 ampere load.

So you're not going to find anyone here on this forum who will tell you this is OK to do. It's a code violation. It's dangerous if anything goes wrong. And the personal liability could cost you your home and business.

There's also one more thing to consider that I think about a lot. If I did some sub-standard trick and someone was injured or killed, I would have to live with that guilt for the rest of my life. That's why I insist that everything is done as safely as possible, and many times we go beyond the basic code requirement since it can't account for EVERY crazy thing we have to do. The National Electrical Code is a MINIMUM requirement, and it's up to the installer and inspector to judge if it's adequate as written or you need to be even tougher on yourself. I always try to error on the side of safety. 

Stephen Swaffer

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Re: Voltage sag solution?
« Reply #14 on: March 14, 2017, 10:32:14 pm »

Keep in mind, with regards to the "death adapter" comment.  You might say, "Duh, we'd always unplug both connectors for safety."  This may or may not be reasonable-but 175' away where the cords are plugged into the receptacle it might not be obvious that the 2 cords are "Y'd" together-so unsuspecting person unplugs one cord-seeing nothing bad happen, they plug in their personal electronic device to recharge it, leaving a hot prong laying there for an unsuspecting person to grab onto.

When dealing with safety, it is easy to defend against reasonable things you expect to happen.  Unfortunately, to be effective you have to defend against the things that no one would ever do because it defies reason to do so-but someone will eventually dream up some reason they should be the ones to defy common sense.
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Steve Swaffer

David Allred

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Re: Voltage sag solution?
« Reply #15 on: March 15, 2017, 01:31:50 pm »

If the offending unit is a PXL3102, will a UPS resolve momentary interruptions from voltage sag?
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Tim McCulloch

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Re: Voltage sag solution?
« Reply #16 on: March 15, 2017, 01:47:53 pm »

If the offending unit is a PXL3102, will a UPS resolve momentary interruptions from voltage sag?

Until it dies, it's possible.  The 3102 draws 9.5 amps at 1/8 power.  If this happens even 15 seconds out of each minute you'll run out of battery sooner or later.  Think about this:  if the circuit can't run the amp, how will it recharge the battery as you're running at a net loss?

Seriously, David.  FATTER WIRE.  I learned the hard way back when I was 'the guy with a van load of PA' and I've tried to not repeat those mistakes; it is not necessary for you to repeat MY mistakes, either. ;)  Oh, and for what you'd spend on a UPS that could actually do what you propose, you could buy a whole lot of larger gauge cable.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

David Allred

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Re: Voltage sag solution?
« Reply #17 on: March 15, 2017, 02:37:19 pm »

Until it dies, it's possible.  The 3102 draws 9.5 amps at 1/8 power.  If this happens even 15 seconds out of each minute you'll run out of battery sooner or later.  Think about this:  if the circuit can't run the amp, how will it recharge the battery as you're running at a net loss?

Seriously, David.  FATTER WIRE.  I learned the hard way back when I was 'the guy with a van load of PA' and I've tried to not repeat those mistakes; it is not necessary for you to repeat MY mistakes, either. ;)  Oh, and for what you'd spend on a UPS that could actually do what you propose, you could buy a whole lot of larger gauge cable.
It is a simple repeat gig.  Middle school graduation at a football field.  1 mic and music during their walk up the track and into the stands.  I had one reboot of the amp during music only when I pushed a bit.  If I can get through the first 5 mins, the rest is cake.  The school is running cords.  They are heavier than 16 awg (that I listed).  I can have them (or do myself) run a 2nd line from the end zone scoreboard.  I am also going to see if anyone has a small Honda genny, or one that maybe a parent can loan to the school.  If I can get the amp on a separate run (or genny) I shouldn't have any problems.
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Mike Sokol

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Re: Voltage sag solution?
« Reply #18 on: March 15, 2017, 03:10:14 pm »

It is a simple repeat gig.  Middle school graduation at a football field.  1 mic and music during their walk up the track and into the stands.  I had one reboot of the amp during music only when I pushed a bit.  If I can get through the first 5 mins, the rest is cake.  The school is running cords.  They are heavier than 16 awg (that I listed).  I can have them (or do myself) run a 2nd line from the end zone scoreboard.  I am also going to see if anyone has a small Honda genny, or one that maybe a parent can loan to the school.  If I can get the amp on a separate run (or genny) I shouldn't have any problems.

I have a few of the little Honda Inverter generators, and they're perfect for this sort of gig. You can run several amplifiers from an EU2000i, and we've even run small outside stages from an EU3000i.
« Last Edit: March 16, 2017, 12:29:26 am by Mike Sokol »
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Stephen Swaffer

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Re: Voltage sag solution?
« Reply #19 on: March 15, 2017, 11:31:01 pm »

It is a simple repeat gig. 

It's simple with the right equipment-and proper power is just as important as the right amps or speakers.  If you rely on others to help out you will almost always have to work harder.  As a contractor, people always want to save money by providing materials or helping-but they simply don't understand what it takes to do it right.

Perhaps you could talk the school into buying a cord(or a genny)-but where will it be next year?  OTOH, if you buy a heavy cord (or genny) then you are THE provider with the right gear to do this simple gig.  You know what you are doing and it  is an easy call for the administrator to call David and check that box for the graduation.  Make it easy for them to hire you and make it easy for yourself to do the job and in the long run you'll come out ahead.
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Steve Swaffer
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