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#212067 12/08/13 06:18 PM
Joined: Feb 2013
Posts: 264
Potseal Offline OP
Member
We're running power for medical equipment. The equipment comes with a service manual. In the service manual it mentions "D type grounding". Here is all the information as it is stated in the manual:

"Ground Terminal

Grounding resistance should be less than 100 ohms (D type grounding) ground terminal. Use a single ground to earth. Do not share with other electrical apparatus."


Never heard of "D type grounding". Based on the description it sounds like an "isolated ground" but since it's referring to the "ground terminal" I'm not certain. Anybody familiar with the term "D type grounding"?

Last edited by Potseal; 12/08/13 06:18 PM.

A malfunction at the junction
--------------------------------------
Dwayne
Joined: Dec 2000
Posts: 4,287
Member

Could it by chance mean "dedicated ground"?

Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
The instructions appear to call for a ground that violates our code. Better have a chat with the inspector.

Joined: Feb 2003
Posts: 367
M
Member
Never heard of that term either but looking at Google shows referenced to class A thru D grounding.

Some installation manuals that are in the search seem to be from Europe / Asia and have the line:
D type Grounding (grounding resistance is lower than 100 ohms)

Last edited by mbhydro; 12/08/13 11:14 PM.
Joined: Jul 2004
Posts: 9,662
Likes: 4
G
Member
They mean isolated ground. You run a dedicated, insulated conductor way the way back to the grounding electrode. You don't share "that conductor" with any other apparatus.

That commonly gets misunderstood to mean you drive a separate rod. That is not right.


Greg Fretwell
Joined: Jun 2004
Posts: 1,273
T
Member
All grounding conductors have to be bonded to the neutral back at the SERVICE.

Truly isolated grounds have been tried -- and they ended up causing the whole dang structure to burn down to the ground during lightning strikes. (Florida)

It's essential to establish an equapotential voltage plane. That stops instantaneous arcs from jumping during lightning events -- or other weird transients -- such as a nearby transformer fault. (traffic collision)



Tesla
Joined: Feb 2013
Posts: 264
Potseal Offline OP
Member
At some point I will meet the tech from the company who is supplying the equipment and he will likely confirm that "D type grounding" is in fact an "isolated ground". Until then, thank-you for the replies.


A malfunction at the junction
--------------------------------------
Dwayne
Joined: May 2005
Posts: 984
G
Member
I have run into quite a few cases where the terminology ended up being the enemy.
I would suggest that you draw up what you want to provide and ask the tech to look at it. That works out better than agreeing on what to call it...only to find out later on that your definition differs from his.

Case in point; I have run across at least 3 meanings of the term 'dedicated circuit'. All of them being equally right (or equally wrong) since NEC does not define the term.


Ghost307
Joined: Feb 2013
Posts: 264
Potseal Offline OP
Member
Originally Posted by ghost307
I have run into quite a few cases where the terminology ended up being the enemy.
I would suggest that you draw up what you want to provide and ask the tech to look at it. That works out better than agreeing on what to call it...only to find out later on that your definition differs from his.

Case in point; I have run across at least 3 meanings of the term 'dedicated circuit'. All of them being equally right (or equally wrong) since NEC does not define the term.


Excellent advice. Thank-you.


A malfunction at the junction
--------------------------------------
Dwayne
Joined: Apr 2002
Posts: 7,279
Likes: 3
Member
Ghost307:
I agree that your suggestion is excellent, and well said.

My opinion of the OPs question, I would lean toward a EGC straight back to the source panel.



John
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