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[Kevin Conlon]

We set up at a car dealer 200 feet from power. Two 123 volt outlets on each side of the breaker pannel, 246 volts total when metered. I made a cable some years ago with two 120 plugs to a stove plug for the distro. I have used it a few times, no problems. When the band is playing hard max draw is around 7-8 amps per leg. My question, is this a safe way to get 240v ? Grounds are tied together. The weird part last week was each leg at the distro was 123 volts yet input volts were 236 or so. I felt safe with it and we used it for hours with no issues. Any ideas on where 10 volts went?. There were no hot skins anywhere that i found and warm wires. So..... safe or not? Never happened before.  Thanks for any insight.   Kevin.

[Mac Kerr]

We set up at a car dealer 200 feet from power. Two 123 volt outlets on each side of the breaker pannel, 246 volts total when metered. I made a cable some years ago with two 120 plugs to a stove plug for the distro. I have used it a few times, no problems. When the band is playing hard max draw is around 7-8 amps per leg. My question, is this a safe way to get 240v ? Grounds are tied together. The weird part last week was each leg at the distro was 123 volts yet input volts were 236 or so. I felt safe with it and we used it for hours with no issues. Any ideas on where 10 volts went?. There were no hot skins anywhere that i found and warm wires. So..... safe or not? Never happened before.  Thanks for any insight.   Kevin.

Not safe, not legal, not OK.

Mac

[Kevin Conlon]

Not safe, not legal, not OK.

Mac

I figured someone would say that. I knew it was not legal. Tell me how it is unsafe please, i need an education.

[Mike Sokol]

I figured someone would say that. I knew it was not legal. Tell me how it is unsafe please, i need an education.

The primary danger is that if you have any amplifiers or other gear operating on 240 volts (two hot legs), and one of the male plugs were pulled out of the receptacle, then there would a cross-connect from the still connected male plug to the disconnected male plug. So that would allow 120 volts to appear on the male contact of the disconnected plug. Since any stove plug (I assume you mean a 14-50 receptacle) is rated for 250 volts, then it's assumed there's a potential for two-pole (240-volt) operation. And if that were to occur, it could create a deadly situation.

Most code isn't there for when things are all perfectly correct. It's there to assure there's sufficient backups for when something goes wrong. For example, there's generally no immediate danger to wiring a receptacle with a bootleg ground. But if the polarity was accidentally reversed, then the chassis would be energized with 120-volts at full current capability. A classic RPBG (Reverse Polarity Bootleg Ground).

And while your wiring scenario might work properly if all other conditions were met perfectly, there's just too many things that could go wrong with it for ANY inspector to OK. That's why it's a definite code violation, and you would carry full responsibility (read liability) if something were to go wrong and someone got hurt (or even killed), or gear was damaged.   

Far better to talk the dealership into wiring in a dedicated 14-50 receptacle on its own 2-pole/50-amp breaker. Then you could just plug in without fooling around with an adapter cable that's sure to give any AHJ a heartburn.   

[Mike Sokol]

We set up at a car dealer 200 feet from power. When the band is playing hard max draw is around 7-8 amps per leg.

I've done this exact type of gig for some local car dealerships a few times, and if I'm far from power I either use a Honda EU2000i generator (which works great), or a 2kW sine inverter I have wired into my truck battery (which also works great). No wires laying on the ground for vehicles to run over, and no voltage drop from 200 feet of wiring run.

[Kevin Conlon]

The primary danger is that if you have any amplifiers or other gear operating on 240 volts (two hot legs), and one of the male plugs were pulled out of the receptacle, then there would a cross-connect from the still connected male plug to the disconnected male plug. So that would allow 120 volts to appear on the male contact of the disconnected plug. Since any stove plug (I assume you mean a 14-50 receptacle) is rated for 250 volts, then it's assumed there's a potential for two-pole (240-volt) operation. And if that were to occur, it could create a deadly situation.

Most code isn't there for when things are all perfectly correct. It's there to assure there's sufficient backups for when something goes wrong. For example, there's generally no immediate danger to wiring a receptacle with a bootleg ground. But if the polarity was accidentally reversed, then the chassis would be energized with 120-volts at full current capability. A classic RPBG (Reverse Polarity Bootleg Ground).

And while your wiring scenario might work properly if all other conditions were met perfectly, there's just too many things that could go wrong with it for ANY inspector to OK. That's why it's a definite code violation, and you would carry full responsibility (read liability) if something were to go wrong and someone got hurt (or even killed), or gear was damaged.   

Far better to talk the dealership into wiring in a dedicated 14-50 receptacle on its own 2-pole/50-amp breaker. Then you could just plug in without fooling around with an adapter cable that's sure to give any AHJ a heartburn.

Thank you. I understand. Let me point out that when i have used this setup it has never run anything 240 for the reasons you explained. No AHJ here that ever shows up(yet). We are considering a proper size generator or renting next time. This came up overnight, no time to react. I know this is no excuse. Thanks.
P.S.  Any idea where the 10 volt difference came from. this was essentialy a dual 120 rig. 

[Tim McCulloch]

Thank you. I understand. Let me point out that when i have used this setup it has never run anything 240 for the reasons you explained. No AHJ here that ever shows up(yet). We are considering a proper size generator or renting next time. This came up overnight, no time to react. I know this is no excuse. Thanks.
P.S.  Any idea where the 10 volt difference came from. this was essentialy a dual 120 rig.

At the end of your extensions, or at the source?  How much voltage was between neutral and ground at point of service and at the end of your extensions?

[Kevin Conlon]

At the end of your extensions, or at the source?  How much voltage was between neutral and ground at point of service and at the end of your extensions?

I did not check! I did not notice till all was up and running. Thanks all, i had to know how wrong i was.

[TJ (Tom) Cornish]

Since you didn't use 240 volts, why did you use your distro instead of just using the two extension cords directly?  Your distro doesn't give you any more usable power, and as has been pointed out, increases liability and safety risk fairly significantly.

It's not illegal to combine grounds between multiple circuits - this is in fact the main benefit of the "Poor Man's Distro", the purpose of which is to reduce system noise by bonding grounds of your supply circuits via the power distribution side rather than through all your audio devices.

[Kevin Conlon]

Since you didn't use 240 volts, why did you use your distro instead of just using the two extension cords directly?  Your distro doesn't give you any more usable power, and as has been pointed out, increases liability and safety risk fairly significantly.

It's not illegal to combine grounds between multiple circuits - this is in fact the main benefit of the "Poor Man's Distro", the purpose of which is to reduce system noise by bonding grounds of your supply circuits via the power distribution side rather than through all your audio devices.

I needed the distance. 100 feet ext cord, 100 of #8 for distro.

[TJ (Tom) Cornish]

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.

[Kevin Conlon]

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.

[Stephen Swaffer]

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.

[Kevin Conlon]

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.

[Tim McCulloch]

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).

[Kevin Conlon]

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.

[Rob Spence]

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 didn’t 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, won’t work.



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[Steve-White]

We set up at a car dealer 200 feet from power. Two 123 volt outlets on each side of the breaker pannel, 246 volts total when metered. I made a cable some years ago with two 120 plugs to a stove plug for the distro. I have used it a few times, no problems. When the band is playing hard max draw is around 7-8 amps per leg. My question, is this a safe way to get 240v ? Grounds are tied together. The weird part last week was each leg at the distro was 123 volts yet input volts were 236 or so. I felt safe with it and we used it for hours with no issues. Any ideas on where 10 volts went?. There were no hot skins anywhere that i found and warm wires. So..... safe or not? Never happened before.  Thanks for any insight.   Kevin.

I've done it in the past at a HS stadium graduation ceremony - back in the 80's before I knew better - wouldn't do it again.  Another problem is the breakers aren't ganged together at the panel and you have now configured with L1 L2 250V potential in the circuit.  So, one leg could trip and other remain hot - not kosher.

[ProSoundWeb Community]