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

2 bonded neutrals

<< < (2/3) > >>

Jonathan Johnson:

--- Quote from: TJ (Tom) Cornish on September 20, 2013, 03:29:50 PM ---The result is any ground conductors before the second bond (your distro) potentially become current-carrying - there are effectively two neutral wires returning current - the neutral, and the ground.  The amount of current flowing on each of these wires will be in proportion to the path resistance, and in the event of a neutral wire failure, all return current would be on that ground wire.

Your portable distro should not have a ground-neutral bond unless that's the only bond in the system.

--- End quote ---

In this scenario (where the generator has bonded neutral and ground) you have two options:

* Leave it bonded at the distro, but disconnect the ground conductor that goes to the generator. Connecting other distros or equipment directly to the generator could result in ground loop hum.
* Break the bond at the distro. The grounds and neutrals in the distro should go to separate buses; the neutral bus should be insulated from the chassis of the distro except by the REMOVABLE bond. I think I would prefer this method, as it seems safer and complies with codes.
It may be an option to install an SPDT switch to selectively bond your load grounds to either the neutral or the upstream ground connection. Or you could just make up a "bonding adapter" as Mike suggests and use it when needed, leaving the ground and neutral unbonded in the distro.

Jerome Malsack:
You should look carefully at the switch before you install that because It will need to handle the 20 amps current that can be there.   

Chris Hindle:

--- Quote from: Jonathan Johnson on September 21, 2013, 01:22:24 AM ---... or It may be an option to install an SPDT switch to selectively bond your load grounds to either the neutral or the upstream ground connection. Or you could just make up a "bonding adapter" as Mike suggests and use it when needed, leaving the ground and neutral unbonded in the distro.

--- End quote ---

Switches = BAD
Adapters = Useable

A switch can be set to the "wrong" position too easily.
Adapters, while sometimes clunky and able to get "lost", are put in place when needed, and not likely to get installed/removed by accident.
The real question is, will the fire marshall/inspector accept you workaround, or declare it N/G ??

Jonathan Johnson:

--- Quote from: Chris Hindle on September 27, 2013, 08:58:11 AM ---The real question is, will the fire marshall/inspector accept you workaround, or declare it N/G ??

--- End quote ---

Always comply with the code enforcement officer. If that is not acceptable, present the code enforcement officer with engineering drawings (from an electrical engineer licensed in the state or jurisdiction where the installation is located) showing your preferred method. Then comply with the code enforcement officer. They will usually go with the engineer's specs, but they do have the power to override the engineer.

Craig Hauber:

--- Quote from: Mike Sokol on September 20, 2013, 04:16:46 PM ---Yes, that's correct according to the NEC. However, be aware that many (if not most) smaller (under 5 KW) inverter generators have a floated G-N bond.
--- End quote ---

What's "floated" mean?  Is the ground simply not connected to anything but the metal of the generator housing? 

I have an older style pullstart Generac and haven't actually checked it out but need to use it soon for a homecoming float.  (which brings up a whole other grounding set of questions as the metal framed float trailer is grounded to the vehicle's battery and the whole assembly is on rubber tires.  what happens when generator-run equipment is tied to inverter-run equipment (or car-audio equipment) through the grounds of audio cables?

Navigation

[0] Message Index

[#] Next page

[*] Previous page

Go to full version