Bonding of Isolated Grounding system to plant electrode system, i.e. ground loop

[Dale001289]

Is it permissible to have a removable link installed between an Isolated grounding system i.e., underground copper conductor off a Triad and point where it ties into the Plant grounding electrode system, i.e. ground ring?

 

[petersonra]

Is it permissible to have a removable link installed between an Isolated grounding system i.e., underground copper conductor off a Triad and point where it ties into the Plant grounding electrode system, i.e. ground ring?

There is no requirement that an EGC be continuous.

However I'm not sure that what you are describing is even code legal. The so-called isolated ground goes back to the EGC at the service point not to the grounding electrode system.

 

[Smart $]

There is no requirement that an EGC be continuous.

However I'm not sure that what you are describing is even code legal. The so-called isolated ground goes back to the EGC at the service point not to the grounding electrode system.

The so-called isolated ground goes back to a common EGC point not to the grounding electrode system. Quite often the common EGC point is the EGC/MBJ point at the service.

@Dale001289
The electrode triad can be tied to any point on the EGC system, or it can be tied directly to the grounding electrode system (GES). However, once the triad is in place, it must be and remain connected.

 

[Dale001289]

The so-called isolated ground goes back to a common EGC point not to the grounding electrode system. Quite often the common EGC point is the EGC/MBJ point at the service.

@Dale001289
The electrode triad can be tied to any point on the EGC system, or it can be tied directly to the grounding electrode system (GES). However, once the triad is in place, it must be and remain connected.

Smart: Your last sentence is where I want to focus. The triad will remain connected, however, the 'removable link' constitutes a gap between the triad and point where all other grounding cables connect. To me, this would be violation of 250.50, however, 250.6(B) seems to allow it - then there's 250.8(A) to consider...I'm so confused (looking at 2017 NEC handbook)

 

[ActionDave]

Smart: Your last sentence is where I want to focus. The triad will remain connected, however, the 'removable link' constitutes a gap between the triad and point where all other grounding cables connect. To me, this would be violation of 250.50, however, 250.6(B) seems to allow it - then there's 250.8(A) to consider...I'm so confused (looking at 2017 NEC handbook)

Any part of the grounding electrode system can be removable other than the one required by 250.64(C) to be continuous. Look at 250.70.

 

[Smart $]

Any part of the grounding electrode system can be removable other than the one required by 250.64(C) to be continuous. Look at 250.70.

Removable, yes... provided minimum or required electrodes are maintained. Electrodes have to physically be removed or otherwise rendered 'not an electrode'. They cannot just be disconnected. But Dale wanting a removable link suggests to me he does not want to remove the triad electrodes.

@Dale001289
Exactly what are you seeing as objectionable current requiring the application of 250.6(B)? How would 'unlinking' the triad result in stopping objectionable current that isn't also and will remain on the GES in general?

 

[Dale001289]

Removable, yes... provided minimum or required electrodes are maintained. Electrodes have to physically be removed or otherwise rendered 'not an electrode'. They cannot just be disconnected. But Dale wanting a removable link suggests to me he does not want to remove the triad electrodes.

@Dale001289
Exactly what are you seeing as objectionable current requiring the application of 250.6(B)? How would 'unlinking' the triad result in stopping objectionable current that isn't also and will remain on the GES in general?

The sole connection to plant grounding system as required by 250.50 can result both common mode noise and objectionable currents. The removable link allows the field to 'trouble-shoot' the isolated grounding system and theoretically eliminate both.

 

[roger]

The sole connection to plant grounding system as required by 250.50 can result both common mode noise and objectionable currents. The removable link allows the field to 'trouble-shoot' the isolated grounding system and theoretically eliminate both.

A single connection (as in sole) of the GES does not cause a ground loop, ground loops are caused by multiple connections. Your best solution would be to remove the "magical triad".

Roger

 

[Dale001289]

Mainly it's about common mode noise - not a loop


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[roger]

Mainly it's about common mode noise - not a loop

So why not provide a link to the isolated ground system in the service equipment where it can be accessed for testing? As mentioned in post #2, this isolated EGS should not connect to the GES itself.

Roger

 

[Dale001289]

I agree the 'link' should occur in an accessible location. I just have to convince the client his idea is not a good one.


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[Smart $]

The sole connection to plant grounding system as required by 250.50 can result both common mode noise and objectionable currents. The removable link allows the field to 'trouble-shoot' the isolated grounding system and theoretically eliminate both.

Mainly it's about common mode noise - not a loop

I agree the 'link' should occur in an accessible location. I just have to convince the client his idea is not a good one.

All I see is someone looking for a reason to leave the EGS and the triad disconnected, i.e. completely isolate the equipment from the EGS. Doing so violates the listing for all equipment furnished with a ground prong or terminal.

 

[Dale001289]

Bonding of Isolated Grounding system to plant electrode system, i.e. ground loop

Smart-clientes love to do this . They hate the fact that a 'noisy, dirty' GES is connected to their precious DCS and PLC shields - i.e. isolated GES or Triad
Unfortunately doing so is a violation of 250.50


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[ActionDave]

Smart-clientes love to do this . They hate the fact that a 'noisy, dirty' GES is connected to their precious DCS and PLC shields - i.e. isolated GES or Triad
Unfortunately doing so is a violation of 250.50


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Dirt Worshipers can not be reasoned with.

 

[Dale001289]

Agreed


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[roger]

Dirt Worshipers can not be reasoned with.

:thumbsup:
Remember, a triad is in the shape of a cone foil hat and every-bit as effective.

Roger

 

[Smart $]

Smart-clientes love to do this . They hate the fact that a 'noisy, dirty' GES is connected to their precious DCS and PLC shields - i.e. isolated GES or Triad
Unfortunately doing so is a violation of 250.50

It's a bleed over from one particular type of IEC grounding that is permitted. Tell them to get a backbone and do it the American way. :lol:

 

[Dale001289]

It's a bleed over from one particular type of IEC grounding that is permitted. Tell them to get a backbone and do it the American way. :lol:

I will do everything I can to convince them. The 'removable link' will be removed and will NEVER find its way home again.

 

[petersonra]

I will do everything I can to convince them. The 'removable link' will be removed and will NEVER find its way home again.

JMNSHO.

If they have paid for this link, and it is code legal, you have an obligation to provide it unless they authorize its removal.

 

[Smart $]

JMNSHO.

If they have paid for this link, and it is code legal, you have an obligation to provide it unless they authorize its removal.

Using it to disconnect from the GES is noncompliant.... period.