Isolated ground wire run indepently

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anbm

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We have an radiology equipment which requires both ground + isolated ground wires. The electrical panel (H1) that feeds this radiolody equipment doesn't have an isolated ground bar.

From radiology equipment will we run ground + isolated ground wires in same conduit back to panel 'HA', the regular ground wire will be bonded to equipment ground bar in panel 'HA'. From panel 'HA', the isolated ground wire shall continue to run in a separate conduit and be terminated to nearest building groounding system (i.e building steel, water metal pipe) without going back to main building service source switchboard. Will this acceptable?

Because if we run this isolated ground wire all the way back to main service switchboard, we have to shut down all panels upstream of 'HA' until the isolated ground wire reachs the main service switchboard and this can create problem, cost issue. Thanks!
 
don_resqcapt19

don_resqcapt19

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No. The isolated EGC must be run with the feeder conductors back to the location of the main bonding jumper for a service supplied system or to the location of the system bonding jumper for a SDS supplied system. It can never just be run to the nearest building steel or water pipe.
 
Buck Parrish

Buck Parrish

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Aghreed and was wondering. Can you use the conduit as your equipment ground? That might help.
Check out 517. 19 F in accordance with 250.118
 
don_resqcapt19

don_resqcapt19

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In this case it may be a cheaper option to install a transformer for this load and then you can run the transformer grounding electrode conductor by itself to the grounding electrode. The isolated grounding conductor must end at the system bonding jumper for the transformer.
 
Buck Parrish

Buck Parrish

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Dennis Alwon said:
Buck this does not help get the isolated ground back to the service.
Click to expand...

He also aked "Will this be acceptable" to run the ground in a separate conduit. That's why I mentioned 517.19(F)

I like Don's ideal about the transformer, That's how I did the dentist office. Then we only dealt with branch isolated conductors.
 
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anbm

Senior Member
don_resqcapt19 said:
No. The isolated EGC must be run with the feeder conductors back to the location of the main bonding jumper for a service supplied system or to the location of the system bonding jumper for a SDS supplied system. It can never just be run to the nearest building steel or water pipe.
Click to expand...

Can you give me the code section address this? because the main bonding jumper also tie to building groun system (building steel, water metal pipe), doesn't it? So why we can't tie the IG wire there directly? Just curious...
 
jumper

jumper

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anbm said:
300.3(B) doesn't say anything about "isolated ground" wire.
Click to expand...

Nor does it say that it is excluded.

For Receptacles, it it reinforced in 250.146(D)

(D) Isolated Receptacles. Where installed for the reduction
of electrical noise (electromagnetic interference) on the
grounding circuit, a receptacle in which the grounding terminal
is purposely insulated from the receptacle mounting
means shall be permitted. The receptacle grounding terminal
shall be connected to an insulated equipment grounding
conductor run with the circuit conductors.
 
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Little Bill

Little Bill

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jumper said:
Nor does it say that it is excluded.

For Receptacles, it it reinforced in 250.146(D)

(D) Isolated Receptacles. Where installed for the reduction
of electrical noise (electromagnetic interference) on the
grounding circuit, a receptacle in which the grounding terminal
is purposely insulated from the receptacle mounting
means shall be permitted. The receptacle grounding terminal
shall be connected to an insulated equipment grounding
conductor run with the circuit conductors.
Click to expand...

It also says "...so as to terminate within the same building or structure directly at an equipment grounding conductor terminal of the applicable derived system or service."
 
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