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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Jamin Lynch on August 31, 2014, 05:33:56 pm

Title: Power from 2 buildings
Post by: Jamin Lynch on August 31, 2014, 05:33:56 pm
I have a small street party coming up in the downtown area. There will be a small stage and I'm sure power will be an issue. I was told the sound company last year ran extension cords and pulled power from one the buildings closest to the stage. But it was a really small set up. I'm brining something a little larger. I can do it with 3 20amp circuits. They said no generators.

My question is, would there be a potential problem if I got power from 2 different buildings? Since the stage will be in the middle of the street could I get power from buildings from opposite sides of the street if needed? What kinds of problems might come into play? What about ground issues?

Thanks
Title: Re: Power from 2 buildings
Post by: Stephen Swaffer on August 31, 2014, 05:47:08 pm
http://forums.prosoundweb.com/index.php/topic,150258.0.html

Check out this topic for a pretty thorough discussion from a few weeks ago.
Title: Re: Power from 2 buildings
Post by: Jeff Bankston on August 31, 2014, 07:15:13 pm
no issue "IF" the same transformer powers both buildings. look at the power polls for transformer(s) and service drops or a transformer pad(s). if theres one transformer with a service drop to each building it will not be an issue. as long as your extensions cords have ground wire grounding is not an issue. you need to do a voltage drop caluculation to see what gauge cords to use.

i do not know if there will be a problem if they are fed from seperate transformers. its a question that needs the correct answer.
Title: Re: Power from 2 buildings
Post by: g'bye, Dick Rees on August 31, 2014, 07:53:54 pm
They probably mean no LOUD  generators...
Title: Re: Power from 2 buildings
Post by: Jeff Bankston on August 31, 2014, 07:56:20 pm
They probably mean no LOUD  generators...
i say boy , i say son , i say speakup boy i cant i say i cant hear ya son ! ole Foghorn Leghorn has a case of demented ya.
Title: Re: Power from 2 buildings
Post by: Jamin Lynch on September 01, 2014, 08:56:06 am
http://forums.prosoundweb.com/index.php/topic,150258.0.html

Check out this topic for a pretty thorough discussion from a few weeks ago.

OK I remember seeing this topic. I'll read through it.
Title: Re: Power from 2 buildings
Post by: Jamin Lynch on September 01, 2014, 09:00:04 am
They probably mean no LOUD  generators...

They said no generators due to all the pedestrian traffic. I told them I would barricade it off and post an armed guard...they still said no. I guess they have no problem with extension cords.

If there's not enough power available I'll have to scale back a bit.
Title: Re: Power from 2 buildings
Post by: g'bye, Dick Rees on September 01, 2014, 09:06:36 am
They said no generators due to all the pedestrian traffic. I told them I would barricade it off and post an armed guard...they still said no. I guess they have no problem with extension cords.

If there's not enough power available I'll have to scale back a bit.

That's just stupid.  I've never seen anyone get their feet tangled in a generator...

At some point you have to take the bull(shit) by the horns and not let the idiots tell you how to do your job when the issue involves safety.  I've gone to using my Honda EU3000i for any jobs where I would have to use long cable runs across public space to get to building power.

Title: Re: Power from 2 buildings
Post by: Ray Aberle on September 01, 2014, 09:29:35 am
Hire enough cable ramps to ramp off the AC feeds, at their expense, of course?

-Ray
Title: Re: Power from 2 buildings
Post by: Jamin Lynch on September 01, 2014, 09:31:23 am
That's just stupid.  I've never seen anyone get their feet tangled in a generator...

At some point you have to take the bull(shit) by the horns and not let the idiots tell you how to do your job when the issue involves safety.  I've gone to using my Honda EU3000i for any jobs where I would have to use long cable runs across public space to get to building power.

I agree Dick. When I mentioned the all problems with running extension cords I get the typical response. "That's what the other sound guys did last year."

Damn ankle biters.
Title: Re: Power from 2 buildings
Post by: Mike Sokol on September 01, 2014, 09:44:00 am
That's just stupid.  I've never seen anyone get their feet tangled in a generator...

At some point you have to take the bull(shit) by the horns and not let the idiots tell you how to do your job when the issue involves safety.  I've gone to using my Honda EU3000i for any jobs where I would have to use long cable runs across public space to get to building power.

+1

If you can, suggest that the guys/gals making the decision attend a brief generator demonstration. Then beg, borrow or rent an EU3000 for the day, set it up near the proposed location with traffic cones and safety tape around it, and start it up in eco-throttle mode. They've probably had bad experiences with contractor generators in the past, so here's your chance to educate them about the latest technology. You can do a really nice small to medium outdoor show with a single EU3000, and you can link a pair of them get 6,000 watts in case you want to run LED stage lighting at the same time.

Power from two different buildings is always iffy. It can be done successfully if all the wiring is 100% correct and both buildings are on the same street transformer. But when's the last time you saw old buildings with 100% correctly wired power and perfect extension cords? Plus the trip hazards are indeed a serious consideration.

One other thing you could consider is locating a nearby building with a kitchen that has a 50-amp/240-volt "range" outlet (NEMA 14-50) you can borrow for the day. You should be able to find a local sound company that can rent you some 50-amp distro with a NEMA 14-50 to Hubble or camlock adapter which then feeds properly breakered stage and amp-rack outlets. That's still a lot of heavy cable on the ground which "should" have cable ramps. But certainly having 100 amps of 120-volt power would allow you to do a pretty big gig.
Title: Re: Power from 2 buildings
Post by: Frank DeWitt on September 01, 2014, 01:01:56 pm
+1

If you can, suggest that the guys/gals making the decision attend a brief generator demonstration. Then beg, borrow or rent an EU3000 for the day, set it up near the proposed location with traffic cones and safety tape around it, and start it up in eco-throttle mode. They've probably had bad experiences with contractor generators in the past, so here's your chance to educate them about the latest technology. You can do a really nice small to medium outdoor show with a single EU3000, and you can link a pair of them get 6,000 watts in case you want to run LED stage lighting at the same time.


A smart Honda dealer would jump at a chance to supply a generator for that demo.  Make sure to start the generator BEFORE you enter the building to invite them outside.  That way you get the fun of telling them it is already running.
Title: Re: Power from 2 buildings
Post by: g'bye, Dick Rees on September 01, 2014, 01:08:22 pm
And get/rent an EU6000.  They're even quieter than the 3000.
Title: Re: Power from 2 buildings
Post by: Mike Sokol on September 01, 2014, 04:08:30 pm
I told them I would barricade it off and post an armed guard...they still said no.

How come you get to use an "armed guard" when all I get to use is a sweaty roadie wearing a Metalica t-shirt?  :o
Title: Re: Power from 2 buildings
Post by: Jamin Lynch on September 01, 2014, 05:30:53 pm
How come you get to use an "armed guard" when all I get to use is a sweaty roadie wearing a Metalica t-shirt?  :o

Title: Re: Power from 2 buildings
Post by: Ray Aberle on September 01, 2014, 06:11:43 pm


Yes..... but will Deputy Fife have more then one bullet?
Title: Re: Power from 2 buildings
Post by: Jeff Bankston on September 01, 2014, 07:20:21 pm
Yes..... but will Deputy Fife have more then one bullet?
The Three Stoogies
Title: Re: Power from 2 buildings
Post by: Ray Aberle on September 01, 2014, 08:16:37 pm
The Three Stoogies

*sigh* never make sense will you.....  :-\    "relevance" is such a big word.
Title: Re: Power from 2 buildings
Post by: Seth Albaum on September 01, 2014, 08:36:04 pm
Did it twice. The buildings were near enough to each other they were likely fed by the same transformer, but we divided up the duties. One building was for the powered PA and monitors and the other fed FOH/various. The city I'm in doesn't have adequate power for large outdoor festivals, but our festivals are getting larger and larger.. some day, I hope...
Title: Re: Power from 2 buildings
Post by: Stephen Swaffer on September 01, 2014, 10:43:47 pm
Seth, in theory it should work, but the bottom line is some point in your gear will be the weak link connecting the grounding systems of 2 services-each with its own ground/neutral bond.  As long as all the connections are good, no problems.

Six weeks ago, I went to look at a service for a customer that was not experiencing any problems-we were actually looking to upgrade from a single phase to a 3 phase service for increased capacity.  I noticed one of the covers for the compression connector for the connection from the POCO to customers conductors was lying on the ground-it had melted off.  There were no other symptoms-had this been a neutral connection there would have been no noticeable symptoms and tied to another building that neutral current would look for another easier path.  Do you really want your gear to be that path?  This connection had been in service for some time, we had yet to add any load to it-but we had a problem.  I really don't think you want your gear or cables melting down to be the red flag indicating a problem!
Title: Re: Power from 2 buildings
Post by: Jonathan Johnson on September 02, 2014, 12:48:13 am
Best answer: single generator (or two properly coupled Honda generators) supplying all loads.

Second best answer: balanced audio signal with transformer isolation plus ground lift between devices on separate power sources.

(Edited to clarify that I mean audio signal. The idea of the audio isolation transformer with ground lift is so that there is no direct electrical path between devices that are connected to different power sources, which will prevent hum due to differing ground potential, and may help reduce the possibility of electrical shock or equipment damage in the event of an electrical fault.)
Title: Re: Power from 2 buildings
Post by: Jeff Bankston on September 02, 2014, 01:42:19 am
Best answer: single generator (or two properly coupled Honda generators) supplying all loads.

Second best answer: balanced signal with transformer isolation plus ground lift between devices on separate power sources.
they might need to hire an electrician especially for the 2nd best answer unless the op is a journeyman electrician with the knowledge on how to configure it.
Title: Re: Power from 2 buildings
Post by: Mike Sokol on September 02, 2014, 07:27:17 am
they might need to hire an electrician especially for the 2nd best answer unless the op is a journeyman electrician with the knowledge on how to configure it.

Ref: "Second best answer: balanced signal with transformer isolation plus ground lift between devices on separate power sources."

He's talking about audio isolation transformers, not power isolation transformers, so no electrician required. A good example of a 1:1 audio isolation transformer is the Whirlwind ISO-2, which according to my experiments and discussions with WW will withstand at least 200 volts common mode differential. So it should survive being between an accidentally miswired 120-volt hot-grounded piece of gear connected to a properly grounded one, but in that instance you'll likely have a shock hazard for musicians. 

A good passive DI box with a ground lift should be used between any stage amps and the mixing console at all times. I like the WW IMP2 boxes for a cost effective solution that's tough as nails. Active DI boxes that don't have isolated phantom power supplies won't provide 100% isolation under high-voltage ground differentials, so I tend not to use them. 

Frank DeWitt on this forum builds a beautiful premium passive DI box. Frank... would you mind stepping up to the plate and describing your DI box to the crowd. This is one-time, self-promotional ticket since we're discussing specific DI box usage under adverse conditions.
Title: Re: Power from 2 buildings
Post by: Keith Broughton on September 02, 2014, 08:23:32 am


He's talking about audio isolation transformers, not power isolation transformers, so no electrician required. A good example of a 1:1 audio isolation transformer is the Whirlwind ISO-2, which according to my experiments and discussions with WW will withstand at least 200 volts common mode differential. So it should survive being between an accidentally miswired 120-volt hot-grounded piece of gear connected to a properly grounded one, but in that instance you'll likely have a shock hazard for musicians. 

A good passive DI box with a ground lift should be used between any stage amps and the mixing console at all times. I like the WW IMP2 boxes for a cost effective solution that's tough as nails. Active DI boxes that don't have isolated phantom power supplies won't provide 100% isolation under high-voltage ground differentials, so I tend not to use them. 

Frank DeWitt on this forum builds a beautiful premium passive DI box. Frank... would you mind stepping up to the plate and describing your DI box to the crowd. This is one-time, self-promotional ticket since we're discussing specific DI box usage under adverse conditions.
With this solution in mind, you could power the PA and FOH from one building and the stage from another. Use iso transformers for any direct connection to the stage gear.
Title: Re: Power from 2 buildings
Post by: g'bye, Dick Rees on September 02, 2014, 11:44:53 am
With this solution in mind, you could power the PA and FOH from one building and the stage from another. Use iso transformers for any direct connection to the stage gear.

Yup.

But there's still the issue of tripping hazards/traffic and now it's doubled.  It took me a long time to do it, but at this point I walk away from any jobs where the sponsors place such strictures on me.  It's just not worth it.  And when (not if) something goes wrong, even a show stoppage from a tripped and inaccessible breaker, guess who's going to get the blame.

And where do you place your GFCI's?

Title: Re: Power from 2 buildings
Post by: Tim McCulloch on September 02, 2014, 12:50:20 pm
Yup.

But there's still the issue of tripping hazards/traffic and now it's doubled.  It took me a long time to do it, but at this point I walk away from any jobs where the sponsors place such strictures on me.  It's just not worth it.  And when (not if) something goes wrong, even a show stoppage from a tripped and inaccessible breaker, guess who's going to get the blame.

And where do you place your GFCI's?

This, ladies and gentlemen, is the Voice of Experience.  Listen well and heed the advice given.

Ignore any accordion. 8)
Title: Re: Power from 2 buildings
Post by: g'bye, Dick Rees on September 02, 2014, 12:57:26 pm
This, ladies and gentlemen, is the Voice of Experience.  Listen well and heed the advice given.

Ignore any accordion. 8)

I'd like to dedicate this next number to a long-time fan from Wichita...

Don't forget to tell the sponsors that your cost will include the rental of several hundred feet of yellow jackets...
Title: Re: Power from 2 buildings
Post by: Ray Aberle on September 02, 2014, 01:27:49 pm
I'd like to dedicate this next number to a long-time fan from Wichita...

Don't forget to tell the sponsors that your cost will include the rental of several hundred feet of yellow jackets...

I am sure there are plenty available in Corpus Christy, TX.

On the other hand, owning a hundred-hundred fifty feet of Checkers Guard Dogs has been pretty nice the past three years-- not only do I get to use them for my events ("that's ten bucks each for these, thank you very much"), but I can rent them to other companies. Since I splurged and had my logo impressioned on the lid, it's cool renting them to other sound companies, who are advertising my company for me, at their event. :D

Since they rent for so little, that's such a small amount that big events don't even notice the cost. And for a smaller event, if I can give them 60' of ramps for free and it gets me the gig- well, that's a rental item I am OK not always charging for. Makes the customer feel good.

-Ray "who is listening to online streaming radio and wigging out about the trainwrecks" Aberle


...ouch, another one!