ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2]  All   Go Down

Author Topic: Could this cause a problem?  (Read 1098 times)

TJ (Tom) Cornish

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 4148
  • St. Paul, MN
Re: Could this cause a problem?
« Reply #10 on: November 05, 2018, 10:06:46 am »

I needed the distance. 100 feet ext cord, 100 of #8 for distro.
What plug is on the end of your distro?  NEC requires that over-current protection be installed UPSTREAM of all lesser-rated distribution, meaning that unless you have a 30A plug on your wire or a 30A circuit breaker at the male end of your distro, you are probably undersized.  Plugging your #8 wire into a 14-50 is definitely a problem, even if you only have a couple 20A circuits in your distro, as a fault in the #8 wire could cause the wire to overheat but not draw enough current to trip the 50A breaker in the venue.

Speaking generally now - the era of home-made power distros is effectively over.  NEC2017 now requires all portable power distribution to be listed (meaning a completed assembly made by a listed shop) rather than an assembly of listed components (aka homebrew).  Once you need more power than a couple circuits can provide, the next stop is a commercially-available UL-listed spiderbox.  After that, it's time for gear made by Motion Labs/Whirlwind/Lex/etc.  The cost of this - both the distribution equipment and the supply (e.g. generator rental) needs to be factored into the show.  If the show can't support the logistics to get the job done, don't try to be a superhero - let the show fail without you.
Logged

Kevin Conlon

  • Full Member
  • ***
  • Offline Offline
  • Posts: 205
Re: Could this cause a problem?
« Reply #11 on: November 05, 2018, 10:40:08 am »

What plug is on the end of your distro?  NEC requires that over-current protection be installed UPSTREAM of all lesser-rated distribution, meaning that unless you have a 30A plug on your wire or a 30A circuit breaker at the male end of your distro, you are probably undersized.  Plugging your #8 wire into a 14-50 is definitely a problem, even if you only have a couple 20A circuits in your distro, as a fault in the #8 wire could cause the wire to overheat but not draw enough current to trip the 50A breaker in the venue.

Speaking generally now - the era of home-made power distros is effectively over.  NEC2017 now requires all portable power distribution to be listed (meaning a completed assembly made by a listed shop) rather than an assembly of listed components (aka homebrew).  Once you need more power than a couple circuits can provide, the next stop is a commercially-available UL-listed spiderbox.  After that, it's time for gear made by Motion Labs/Whirlwind/Lex/etc.  The cost of this - both the distribution equipment and the supply (e.g. generator rental) needs to be factored into the show.  If the show can't support the logistics to get the job done, don't try to be a superhero - let the show fail without you.
In this usage there was a 30a on each leg, at the distro, (the wire is #6, not 8, sorry) The wall outlets were 15a, so assuming 12 wire, breakers unknown. Ext. cords came from wall to l14-50, then to distro. All well protected from people. I know my box would not pass a proper inspection. We also tie into breaker panels sometimes, if you really want to kill me on this! The local elect. inspector wanted me to get a licence at one point because he liked my work. I trust what i build and do to be safe, legal or maybe not as much. I will be working to more proper methods as time goes on. Liability makes it needed. I should have asked before, not after. Thanks to all for your points.
Logged

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2067
Re: Could this cause a problem?
« Reply #12 on: November 05, 2018, 12:51:17 pm »

I understand you want to be safe-comments that concern me as to attention to detail in your work:

OP-"Is this a safe way to get 240 volts?"  Later-"Nothing has ever been connected as a 240 volt load"-then why do you care if it is a safe way to get 240-if you only need multiple 120 volt circuits?

"In this usage, there is 30 A on each leg"  "Wall outlets are 15A" "Assuming #12 wire"  So how do you pull 30 amps from a 15 A outlet? 15 A outlets can legally and properly be wired with #14 wire.

IF you are talking 2 male plugs-one for "Phase A" of the distro and one for "Phase B", and there are no 220/240 volt receptacles on the distro end, I see this a relatively safe, if not entirely kosher. 

IF you are talking 2 male plugs for each phase, so 215 amps circuits supplies one 30 amp draw, this is an absolute NO and a huge safety issue-as it is if you are using any 220/240 volts loads or if there is a place to plug them in on the distro.

The lost 10 volts might be explained by the possibility of the 2 circuits being fed by a 3 phase service-as in that case addition for the phases is a vector calculation, not simple addition.
Logged
Steve Swaffer

Kevin Conlon

  • Full Member
  • ***
  • Offline Offline
  • Posts: 205
Re: Could this cause a problem?
« Reply #13 on: November 06, 2018, 07:37:08 pm »

I understand you want to be safe-comments that concern me as to attention to detail in your work:

OP-"Is this a safe way to get 240 volts?"  Later-"Nothing has ever been connected as a 240 volt load"-then why do you care if it is a safe way to get 240-if you only need multiple 120 volt circuits?

"In this usage, there is 30 A on each leg"  "Wall outlets are 15A" "Assuming #12 wire"  So how do you pull 30 amps from a 15 A outlet? 15 A outlets can legally and properly be wired with #14 wire.

IF you are talking 2 male plugs-one for "Phase A" of the distro and one for "Phase B", and there are no 220/240 volt receptacles on the distro end, I see this a relatively safe, if not entirely kosher. 

IF you are talking 2 male plugs for each phase, so 215 amps circuits supplies one 30 amp draw, this is an absolute NO and a huge safety issue-as it is if you are using any 220/240 volts loads or if there is a place to plug them in on the distro.

The lost 10 volts might be explained by the possibility of the 2 circuits being fed by a 3 phase service-as in that case addition for the phases is a vector calculation, not simple addition.
I get the confusion in my statements and my question. We do not use 240 when plugged in this way, that should have been for another day, sorry about that. I sure got my answer. The potential is there for 240 though, should the 240 outlets be covered in this use? I know 14 is fine for 15a. load, and i don't know whats in the wall so never "assume". The breakers on the distro are 30a, just a fact of the build. I can't draw more than the wall offers. It was pointed out as a comment/ answer about where protection needs to be. Also i have little knowledge of 3 phase so i will take your word for the 10volts. Thank you for what you pointed out, i should have thought it through a bit more. Thanks all.            Where's the flogging about tying in to house power panels? I can do without it but i will listen.
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 19239
  • Wichita, Kansas USA
Re: Could this cause a problem?
« Reply #14 on: November 07, 2018, 03:33:06 am »

I get the confusion in my statements and my question. We do not use 240 when plugged in this way, that should have been for another day, sorry about that. I sure got my answer. The potential is there for 240 though, should the 240 outlets be covered in this use? I know 14 is fine for 15a. load, and i don't know whats in the wall so never "assume". The breakers on the distro are 30a, just a fact of the build. I can't draw more than the wall offers. It was pointed out as a comment/ answer about where protection needs to be. Also i have little knowledge of 3 phase so i will take your word for the 10volts. Thank you for what you pointed out, i should have thought it through a bit more. Thanks all.            Where's the flogging about tying in to house power panels? I can do without it but i will listen.

A bunch of basic AC theory here:  http://www.electrician2.com/electa1/electa3htm.htm  It's worth reading even if you don't understand all of it; you can get a feel for what's involved in 3 phase power and loads (hint:  it's all about time, i.e. phase).
Logged
"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

Kevin Conlon

  • Full Member
  • ***
  • Offline Offline
  • Posts: 205
Re: Could this cause a problem?
« Reply #15 on: November 07, 2018, 09:07:54 pm »

A bunch of basic AC theory here:  http://www.electrician2.com/electa1/electa3htm.htm  It's worth reading even if you don't understand all of it; you can get a feel for what's involved in 3 phase power and loads (hint:  it's all about time, i.e. phase).
Thank you Tim. I will read on it as my time permits.
Logged

Rob Spence

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2959
  • Boston Metro North/West
    • Lynx Audio Services
Re: Could this cause a problem?
« Reply #16 on: November 16, 2018, 02:51:36 pm »

Another issue with the two plug cable...

I used to do that years ago at one location and when I tried it at another, it didnít work.

Why? The second location, per code, had CGFI outlets and when I plugged in the 2nd , the GCFI tripped (as it should).

So, if the dealership ever conforms to code for the outlets you use, the technique, not matter how dangerous, wonít work.



Sent from my iPad using Tapatalk Pro
Logged
rob at lynxaudioservices dot com

Dealer for: AKG, Allen & Heath, Ashley, Astatic, Audix, Blue Microphones, CAD, Chauvet, Community, Countryman, Crown, DBX, Electro-Voice, FBT, Furman, Heil, Horizon, Intellistage, JBL, Lab Gruppen, Mid Atlantic, On Stage Stands, Pelican, Peterson Tuners, Presonus, ProCo, QSC, Radial, RCF, Sennheiser, Shure, SKB, Soundcraft, TC Electronics, Telex, Whirlwind and others
Pages: 1 [2]  All   Go Up
 


Page created in 0.055 seconds with 22 queries.