IG receptacles

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nizak

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If there is more than one IG receptacle on a branch circuit is a seperate insulated EGC reccommended for each device? Application is steel emt and thhn conductors. Thanks.
 
nizak said:
If there is more than one IG receptacle on a branch circuit is a seperate insulated EGC reccommended for each device? Application is steel emt and thhn conductors.
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There's absolutely no reason to run more than one IG conductor for one circuit, and one could even suffice for all IG circuits.
 
nizak said:
If there is more than one IG receptacle on a branch circuit is a separate insulated EGC recommended for each device?
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Nope it would be a waste of materials. You are required to bond the EGC to the receptacle case case and yoke, thereby putting all EGC's in parallel or 1 great big conductor in parallel with the EMT. You do not even need the EGC if using EMT, all you need is the IG.
 
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I can not imagine why this would be necessary, I may be wrong: An iso ground to limit "noise"or "loops" should be good for more 1 receptacle I would think.

I type way too slow.
 
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So you could install a jumper wire from the metal box to the "U" terminal on the IG recep and call it good?
 
nizak said:
So you could install a jumper wire from the metal box to the "U" terminal on the IG recep and call it good?
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It would be a good EGC, but it would no longer be an IG. The jumper would defeat (bypass) the IG receptacles insulated grounding terminal.
 
ecirplr said:
Since I have never seen a definition of an IG in the NEC, I have always viewed an IG as an Isolated Ground path. Not a definition but perhaps a description.
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Yes.

So where must it end?

How isolated does it have to be?

My point is there is no NEC standard to apply. The NEC simply gives us permission to run an 'IG' conductor back through j-boxes and panels without connection but does not require that.
 
iwire said:
My point is there is no NEC standard to apply. The NEC simply gives us permission to run an 'IG' conductor back through j-boxes and panels without connection but does not require that.
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Absolutely correct and hence is a design issue, not NEC.
 
The purpose of IG's is to reduce line noise in critical circuits.
The IG, Hot and Neutral wires should have a one to one to one relationship, all in close proximity to each other, all the way back to the service entrance.

This means:
If you Daisy Chain the Hots, then you Daisy Chain the Neutrals and IGs.
If you Home Run the Hots then you Home Run the Neutrals and IGs.
 
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Speedskater said:
The purpose of IG's is to reduce line noise in critical circuits.
The IG, Hot and Neutral wires should have a one to one to one relationship, all in close proximity to each other, all the way back to the service entrance.

This means:
If you Daisy Chain the Hots, then you Daisy Chain the Neutrals and IGs.
If you Home Run the Hots then you Home Run the Neutrals and IGs.
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When installing IG circuits, the IG's were terminated on to an isolated buss, similar to a neutral buss. It then had an insulated GEC back to the grounding electrode system. I do agree it is a design issue and not a NEC issue.
I do not ever recall installing multiple IG outlets on a circuit. It seems that you would be defeating the purpose of the IG circuit by installing multiple outlets.
 
Speedskater said:
The purpose of IG's is to reduce line noise in critical circuits.
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Problem is an IGR is not capable of reducing any noise. It has absolutely no passive or active circuits.

IG form of grounding is only used as a possible means of preventing common-mode noise from entering a circuit on which it is used. It cannot remove or filter any noise already there.

Results of the use of IGR methods range from no effect, desired effect, or worsen the condition.

The most effective means of eliminating common-mode noise is also the least expensive method of using an isolation transformer and employing standard SG receptacles. Even a common dry type every day transformer will reduce CM noise 40 db minimum (10,000 : 1), while special isolation transformer employing electrostatic shields will reduce CM noise by 120 db (1,000,000,000,000 : 1)
 
jumper said:
Why?:-? I am curious.
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Good question and the answer is pretty simple. If you have ever worked with electronic systems that use a DC rectifier of some type, and that is in every thing electronic powered by AC, manufactures have to meet FCC regulations to prevent radio frequency inference or RFI...

Well if you have ever worked on any of the equipment you will notice the manufactures install FR filter caps between L-G and N-G inside the equipment. In addition they might also install surge suppressors like MOV's between L-G and N-G. Well guess what all those do. They all conduct AC line current into GROUND. The current is small, but there none the less.

This is no problem for the equipment injecting the current because at the point of connection the voltage is ZERO with respect to its ground reference. But if you have a another device daisy chained or multiple outlets, that current does develop a voltage potential difference along the length of the IG conductor which corrupts or defeats the purpose. So if those two pieces of equipment share a communication circuit using a grounded signal reference say like a pre-amp and amplifier, that ground reference potential difference is seen as signal and amplified. So the result is an annoying AC HUM in your speakers..
 
I wrote:
"The purpose of IG's is to reduce line noise in critical circuits."
dereckbc said:
Problem is an IGR is not capable of reducing any noise. It has absolutely no passive or active circuits.
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Mr first answer wasn't very clear. Let's try:
An IG will reduce the noise current in a power system or building from using your critical/sensitive circuit signal cables as a parallel return path back to the noise source.
(This still needs work, but it does look a little better)
 
ecirplr said:
I do not ever recall installing multiple IG outlets on a circuit. It seems that you would be defeating the purpose of the IG circuit by installing multiple outlets.
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Recording studios, television studios and larger home theaters all have lots of outlets.
 
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