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Author Topic: Star ground.  (Read 5210 times)

Jerome Malsack

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Jerome Malsack

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Re: Star ground.
« Reply #1 on: March 22, 2017, 08:02:16 pm »

My gut feeling is this is not a recommended answer.  Using multiple Generators or Power from several buildings ?  No not good answer.
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Frank DeWitt

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Re: Star ground.
« Reply #2 on: March 22, 2017, 08:22:30 pm »

5 outputs depend on one of the 5 input cables having a good ground.   The ground return is 1/8 the size of the conductors for the total load.  The one golden grounded input is not labeled.

Be afraid Be very afraid.

 
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Rob Spence

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Re: Star ground.
« Reply #3 on: March 22, 2017, 09:57:40 pm »

How is this any different than the "poor mans distro" ?


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rob at lynxaudioservices dot com

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Mike Sokol

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Re: Star ground.
« Reply #4 on: March 22, 2017, 10:37:15 pm »

The problem with this kind of gadget is that if the single ground fails, then all chassis in the sound system are tied together and a line-to-chassis fault on one circuit will result in a reflected voltage on everything else plugged into it. I'm not so worried about the EGC bus being too small since it's unlikely you'll have multiple line-to-chassis faults at the same time. But this is all grounding eggs in one basket, so that better be a perfect single ground or there will be serious trouble.
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Erik Jerde

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Re: Star ground.
« Reply #5 on: March 22, 2017, 10:48:40 pm »

Saw this on Ebay,  any expert review and comment welcome. 
http://www.ebay.com/itm/Hubbell-Star-Grounding-Five-20A-Input-to-Five-20A-Output-Power-Distro-/282230566364?hash=item41b640addc:g:otQAAOSwA3dYDY5c

No good.  My interpretation of the description is that all output grounds are tied to input 1 ground.  In a PMD all grounds are tied together.  In this case the ground conductor on input one would need to be rated for 100A, not the 20A rated 12ga wife that it's going to be connected to.  The device would also need to be rated to 100a which it's not.
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Rob Spence

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Re: Star ground.
« Reply #6 on: March 23, 2017, 12:08:28 am »

No good.  My interpretation of the description is that all output grounds are tied to input 1 ground.  In a PMD all grounds are tied together.  In this case the ground conductor on input one would need to be rated for 100A, not the 20A rated 12ga wife that it's going to be connected to.  The device would also need to be rated to 100a which it's not.

Ok.


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Keith Broughton

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Re: Star ground.
« Reply #7 on: March 23, 2017, 06:16:06 am »

SOLUTION: Use only one ground source for the entire system.
NO!
The solution is to use transformer isolation between offending components.
+1 on the single ground wire gauge being too small.
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Geoff Doane

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Re: Star ground.
« Reply #8 on: March 23, 2017, 09:42:41 am »

The problem with this kind of gadget is that if the single ground fails, then all chassis in the sound system are tied together and a line-to-chassis fault on one circuit will result in a reflected voltage on everything else plugged into it. I'm not so worried about the EGC bus being too small since it's unlikely you'll have multiple line-to-chassis faults at the same time. But this is all grounding eggs in one basket, so that better be a perfect single ground or there will be serious trouble.

Simply adding ground wires from the other four input flanges to the ground buss would make the device safer and probably more useful.  Although because the original builder pop riveted the flanges in place, it might be difficult to get at those particular terminals.

You don't really care if there are ground currents on the line side of the poor man's distro.  As long as you have your act together with your gear, there shouldn't be anything significant flowing on the load side.  Assuming that the bus bar is good for 100A, connecting all the line grounds at one end, and all the loads at the other should keep the loads at the same potential no matter what happens.

GTD
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frank kayser

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Re: Star ground.
« Reply #9 on: March 23, 2017, 10:06:27 am »

Simply adding ground wires from the other four input flanges to the ground buss would make the device safer and probably more useful.  Although because the original builder pop riveted the flanges in place, it might be difficult to get at those particular terminals.

You don't really care if there are ground currents on the line side of the poor man's distro.  As long as you have your act together with your gear, there shouldn't be anything significant flowing on the load side.  Assuming that the bus bar is good for 100A, connecting all the line grounds at one end, and all the loads at the other should keep the loads at the same potential no matter what happens.

GTD
The box itself is grounded via bus bar, no?  ...and therefore the rivets/flanges.  Why pull rivets to attach ground wires?
Add ground wires from additional inlets ground terminals to the bus bar would effectively turn it into a PMD, so ground wire size would be "handled" and there would be no reliance on that individual input ground system.   So, basically, all this "distro" would do is to get all the inlets and outlets at the same ground potential, correct?
frank
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Re: Star ground.
« Reply #9 on: March 23, 2017, 10:06:27 am »


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