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

Grounding to the neutral bar?

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Steve M Smith:

--- Quote from: TJ (Tom) Cornish on September 19, 2013, 01:23:20 PM --- we can't on a public forum condone what you're doing, no matter how many times you've done it before without apparent issue.
--- End quote ---

And no matter how many time we have done it ourselves!


Steve.

Mike Sokol:

--- Quote from: Steve M Smith on September 19, 2013, 01:34:25 PM ---And no matter how many time we have done it ourselves!

Steve.

--- End quote ---

Everybody chill out a bit. Yes, I also did crazy power connections in the 70's, but I actually went and got my Master's Electricians License in 1978 just so I could flash my card and have access to the power panels. And nowadays liability issues are much greater. If  you can talk the club into installing a simple 50-amp/240-volt 4-wire stove outlet near the panel, you should be able to run most anything you could want from your own distro. And yes, go ahead and meter anything an electrician installs for you, especially in older converted industrial building with 3-phase power. There's something called High-leg delta wiring which is VERY dangerous to connect into. Here's a primer which we can discuss later: http://en.wikipedia.org/wiki/High-leg_delta

As far as looking inside a service panel for a separate or combined Ground-Neutral bus bar, I'm going to say that's beyond the scope of this forum for now. The real problem isn't showing you how everything is SUPPOSED to be wired, but rather how it's ACTUALLY wired. The wiring code has changed a lot over the years, especially in building constructed pre-1970s. So much so that even with my 40-years experience in electrical power I'm sometimes confused trying to figure out exactly what some electrician did to the wiring 30 years ago that could cause a problem today.

At some point I'm going to write an article about panel and sub-panel grounding vs. bonding that should help you all understand this better. But in the meantime, don't tie into any panels unless you're licensed to do so, and let's stay safe out there.... 

Jamin Lynch:

--- Quote from: Steve M Smith on September 19, 2013, 01:34:25 PM ---And no matter how many time we have done it ourselves!


Steve.

--- End quote ---

Whoa! Let's back up. I'm not asking anybody to condone or approve of anything.

Of coarse if a breaker panel looks unsafe, I'll not mess with it. If I burn the place down, I loose my equipment along with it. Everybody looses.

I'm merely asking when inserting my own set of breakers into a panel to connect a distro, is it generally OK to attach the ground wire to the neutral bar when connecting the distro to a main panel? I believe the ground bar and neutral bar are usually bonded together. If it's a sub panel it will most likely have a ground bar and I assume attaching the neutral wire to the neutral bar and the ground wire to the ground bar is probably correct. If there is no ground bar in a sub panel then what would be best practice? Is there something other than "don't use it" that would be a safe option?

Steve M Smith:
I wasn't suggesting we condone anything but I'm sure many of us have done things like this which we shouldn't have done.


Steve.

Greg_Cameron:

--- Quote from: Jamin Lynch on September 19, 2013, 01:59:26 PM ---I'm merely asking when inserting my own set of breakers into a panel to connect a distro, is it generally OK to attach the ground wire to the neutral bar when connecting the distro to a main panel? I believe the ground bar and neutral bar are usually bonded together. If it's a sub panel it will most likely have a ground bar and I assume attaching the neutral wire to the neutral bar and the ground wire to the ground bar is probably correct. If there is no ground bar in a sub panel then what would be best practice? Is there something other than "don't use it" that would be a safe option?

--- End quote ---

Current code stipulates that the neutral bus and ground bus are one in the same at a service entrance or separately derived service since they are bonded. All sub panels downstream from the service entrance are to have neutral and ground un-bonded on separate buses. That topology has been in the NEC since right before the 70s I believe. Any electrical installations prior to that are a crap shoot. Technically, if a sub-panel to be tie into by qualified personnel doesn't have the neutral and ground buses separate, feeder should be run to one that's wired correctly or all the way back to the service entrance if need be to ensure a distro is compliant. Plenty of feeder should be kept on hand for such occasions.

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