What happens if you get to a venue and don't have ground continuity?

IceBurghDJ

DJ Extraordinaire
Apr 17, 2015
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Western Pennsylvania
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I've not worked as a commercial electrician, but did for a couple of years work in residentical new construction. Other than a kitchen (by today's standards that is) there is no rule on how to assign outlets to circuits. Kitchens TODAY the outlets have to alternate circuits as you go around your counter.

Otherwise, 10 outlets or lights can be on one 15a circuit (rule of thumb) and well, whatever is convenient or cheapest or fastest is what is built/wired. If you've had a house and wondered why teh basement ights are on the same circuit as the first floor outlets, or the outlet in the hall is on with the bedroom on the opposite side of the wall this is why.

So if you see a quad outlet 99% of the time it's all the same circuit.

If you see 2 outlets on the same wall - same circuit.

Newer venues, truly commercial ones (say a 10 year old hotel) are probably fine, wired to today's standards.

A 50 year old hotel or vfw or such? Doubtful.

It's only been since maybe 1996 that elec codes have gotten truly involved. When I worked i the early-mid 2000's a typical 3 BR 2 bath house would have 25 circuits in it. My 1937 house, with 2 elec updates/re-wiring and a kitchen/elec panel from 1986 has maybe 10 or 12 - and I put in 3 of those.

Used to be one circuit in a kitched was fine. Now..the microwave, disposal, fridge, stove, overhead light all need their own dedicated 20a circuit PLUS 2 more GFI counter circuits - 7 just for one room. And the dining room these days - 20a for wall sockets and lighting on a different one.

My second floor has ONE circuit for everything. Today? Celing lighting on a diff circuit than wall outlets, each BR on it's own arc fault circuit, the bathroom needs it's own gfi 20a outlet - so 5 minimum today.

But then they've added so many new outlets/requirements - like an outlet within 2' of an entrance to a room, no more than 12' between outlets in a room, 3 way switches. lights/outlets near furnaces and in attics, lights/outlets near exterior doors on the outside of buildings, the type of covers on those outlets, etc.


And I've not read it to see the updates/changes...if you're really bored though...Changes to the 2017 NEC - NFPA - (https://www.nfpa.org/NEC/About-the-NEC/Changes-to-the-2017-NEC)
 

Proformance

DJ Extraordinaire
Nov 6, 2006
3,282
right, but I don't need earth ground to use a GFCI?
Depends on the specific type and it's purpose. For example, modern hair dryers (hand held blower-dryers) have a GFI built into the power cord even though it uses a two prong plug. The device limits return voltage on the neutral. The neutral should carry equal current but minimal voltage relative to the hot side.

besides water, I am trying to imagine what would casue a "ground fault?"
Anything that shorts voltage to the ground. It could be a screw rolling around inside a piece of your gear. Mylar decorations (think "tinsel") are also a dangerous source of electrical shorts. A screw or other sharp object the penetrates a wire. Faulty internal circuits, etc.
 

Proformance

DJ Extraordinaire
Nov 6, 2006
3,282
DJKLEEN, the 3-2 prong adapter (aka cheater plug) is not sanctioned for use without a ground connection. That little green tab you see is supposed to be screwed to the outlet which should be grounded to the box. Using it without a ground connection is a liability that you don't want to be caught with. Besides, if lifting the ground kills the hum then you know you can SAFELY kill the hum with a transformer-isolator.
The green tab on an adapter won't save you if the electrical box is plastic and the ground wire is broken. The center screw and ground are joined only by a bridge upon the frame of the duplex receptacle. In metal boxes the ground wire is supposed to be connected to both the duplex receptacle and the box itself, but this is not always the case. Also, in a metal wall box with an absent or broken ground lead the box is only grounded if it employs a metal conduit which runs all the way back to the main panel.

Lifting the AC ground on your audio system isn't as dangerous as people pose (at least not on DJ level gear.) Most of your gear probably utilizes two prong plugs anyway - and those that don't (like your amplifier) have their own fuses on the input leg. You're also probably deploying multi-outlet strips with fuse and/or surge protection. If anything, the wall plate ground is protecting you from a bad extension cord. :)

Problems occur in old buildings because along with modern NMB type wiring flexible metal conduits (which in prior times served as the ground connection) may still be active in the building and providing alternate ground paths where they come in contact with water pipes, hanger and truss systems, antenna towers, or circuits with combined old and new wiring.

Inserting a Hum-X is really no different than using the adapter. They both have similar risks. If you're using a Hum-X or adapter it's because you have multiple ground loops occurring and no obvious bridge point where you can insert a transformer. This is likely to happen when you combine video projectors and gear whose interlinks you can't easily isolate, along with powered speakers, and other remote gear.

"Ground loop" is usually plural. Sometimes you can locate a single point of initiation and isolate that but, when present loops are occurring in multiplicity throughout the system. This is why sometimes you take action that reduces but does not eliminate the hum.
 
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sawdust123

DJ Extraordinaire
Nov 10, 2006
196
56
Ventura County, CA
Proformance, you are correct that many two prong outlets are grounded incorrectly. I was just pointing out that that 3-2 adapter is only considered safe if the outlet is properly grounded.

The internal fusing of a device or the breaker in a power strip will not save you from electrocution if there is a fault. It is only there for over-current protection. You can have a fault that is high enough impedance to not trip a breaker but low enough impedance to kill you. That is why it is important to use proper grounding techniques.

Video can be a source of ground loops but there are video isolators out there but they are not as easy to find. Fiber links can be good for this purpose.
 

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
Proformance. There was nothing else connected to the signal chain or even power at this time. I went from speaker staight to the wall.
 

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
the DB Tech ES1203. It didn't do it last gig, so definitely power related from the venue.

With that said, the last gig, I actually had a ground loop as there was just so many pieces of equipment (500 person Farmers Open event) including the full slew of PSAV stuff which I was patched into for fill. I was forced to use the Hum X since the XLR ground loop thing I have did not work. Not sure why one would work and the other would not.

What's the reason for that?

I am thinking about getting this--
https://www.amazon.com/Ebtech-HE-2-XLR-Eliminator-2-Channel-Jacks/dp/B00101WA4C/ref=sr_1_6?ie=UTF8&qid=1548541040&sr=8-6&keywords=Ebtech+Hum+X

What are your thoughts?
 
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ittigger

Hundred Acre Industry Icon
Feb 1, 2011
12,911
Western Maryland
If you had many pieces of equipment, they were likely plugged into separate circuits. This can absolutely cause a ground hum - as the separate circuits may have separate connections and resistance to ground.

I have used the Ebtech (line level) Hum Eliminator as shown - and it removes any hum coming through those cables. It will not remove it if it's coming into the amp from the wall.
 

jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
so you used it and it worked?

Not sure I follow-- "any hum coming through those cables."

but not from the wall???
 
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jaswrx

DJ Extraordinaire
Feb 15, 2015
198
33
still trying to better understand... You can either get rid of ground loop three ways.

1. An in-line XLR barrel isolation adapter

2. A direct box (not sure if every DI box does this) like the one shown although it might have more going on in there to get rid of hum.

3 A device like the Ground X which plugs into the device (max 6 amps though).

Is there a situation where one would be better than the other?


1, 2, being the safest? Is there any downside to using these DI boxes or XLR barrel isolation adapters.
 
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steve149

Veni, Vidi, Lusi
Staff member
Sep 26, 2011
32,436
Prospect, CT
still trying to better understand... You can either get rid of ground loop three ways.

1. An in-line XLR barrel isolation adapter

2. A direct box (not sure if every DI box does this) like the one shown although it might have more going on in there to get rid of hum.

3 A device like the Ground X which plugs into the device (max 6 amps though).

Is there a situation where one would be better than the other?


1, 2, being the safest? Is there any downside to using these DI boxes or XLR barrel isolation adapters.
As Tigger said, it depends. You get ground loops (which causes the hum) typically when there is a voltage differential between 2 (or more) devices grounds. That might be between a source and a mixer .. might be between a mixer and a speaker .. might be between the mixer and the outlet. The first 2 things you cite are for issues arising from the potential differences between devices. Lifting the ground (#1) on 1 device or isolating the signal through a transformer (#2) might work. If the issue is with voltage potentials from the wall, then the AC devices might work (just need to make sure there is still a true ground connection left).
 
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jaswrx

DJ Extraordinaire
Feb 15, 2015
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so it sounds like having both is a good idea since it depends on the situation...

I, for one, DO NOT have any ground loops in my system so any hum I get is b/c of the venue, and is out of my control unless I use something like a Hum X. Are there any other devices like Hum X?
 

steve149

Veni, Vidi, Lusi
Staff member
Sep 26, 2011
32,436
Prospect, CT
so it sounds like having both is a good idea since it depends on the situation...

I, for one, DO NOT have any ground loops in my system so any hum I get is b/c of the venue, and is out of my control unless I use something like a Hum X. Are there any other devices like Hum X?
Isolation transformers ( like https://www.amazon.com/Tripp-Lite-IS1000HG-Isolation-Transformer/dp/B00008YMZO?tag=techhivecom-20&ascsubtag=US-003-3063590-002-1434517-web-20 )

and some UPS devices ( like https://www.amazon.com/Tripp-Lite-SmartOnline-Double-Conversion-SU1000XLCD/dp/B00COIZW4A?tag=techhivecom-20&psc=1&ascsubtag=US-003-3063590-002-1434519-web-20)

will isolate grounds as well. Whether they're worth it or not ??? Personally, I will do what's necessary to run all the audio off a single receptacle. I bought a pair of 25 ft AC+XLR and a pair of 35 ft AC + 2 XLR cables so I can run power and signal to my speakers from my table.
 
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jaswrx

DJ Extraordinaire
Feb 15, 2015
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Thanks, Steve. I always run everything on one single outlet too.

I use the combo cables like you too. I can't imagine running sperate XLR and power.
 
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WireNut

DJ
Nov 29, 2010
11
Michigan
I always put equipment on the same circuit on a single outlet.

So are you saying it's still possible to be "grounded" through a shared common ground even though it is not conected to the earth?
The equipment ground (at receptacle) is bonded to the "grounded conductor" usually called, but not always the neutral at the main service panel. The grounded conductor also is bonded to the building piping, ground rods, rerods, building steel, etc. through a grounding electrode conductor. The equipment ground helps facilitate the over current device (breaker/fuse) to open quickly during a ground fault. Grounding electrode conductors, equipment grounding conductors and the grounded conductor are the most important wiring in a building...for safety. Thats my opinion and I'm sticking to it :)