Feeder using conduit as the ground

[mshields]

I am working on the design of an outpatient clinic, essentially a medical office building type of facility, located in a building that used to be a hospital, recently reclassified as Business Use. Against my advice, the client wants to save money by utilizing existing feeders to this space all of which consist of 3 phase and a neutral, utilziing the rigid steel conduit as the ground. Here are my questions:

1. The requirements of a redundant ground for healthcare facilities notwithstanding, is it still permissible to use the conduit as a ground?

2. Since it is a healthcare facility, patient care area's need to be wired in accordance with 517.13, i.e. with a redundant ground. Does that redundant ground have to go all the way back to the source. I would think that the answer is yes and therefore the existing feeder, lacking as it is of an insulated equipment grounding conductor would render this installation non-compliant. Do you agree?


Thanks,

Mike

 

[augie47]

As a non-patient care area, a wiring method listed in 250.118 is suitable as a feeder equipment ground.
In critical care areas, 517.19(D) requires that the feeder raceway or cable have additional bonding.
So it is likely your feeders were Code compliant with patient care at the time of installation

 

[kwired]

As a non-patient care area, a wiring method listed in 250.118 is suitable as a feeder equipment ground.
In critical care areas, 517.19(D) requires that the feeder raceway or cable have additional bonding.
So it is likely your feeders were Code compliant with patient care at the time of installation

I think you meant 517.19(E) or hope you meant (E) because I read (D) several times and wondered if I was missing something, then I read (E) and things started making more sense.

Also 517.13, the section that requires "redundant grounding" in general, only mentions branch circuits.

 

[George Stolz]

Mike, I am confused. Are the feeders going to be serving patient care areas?

If so, the redundant grounding is required back to the panel as mentioned by kwired.

 

[augie47]

I think you meant 517.19(E) or hope you meant (E) because I read (D) several times and wondered if I was missing something, then I read (E) and things started making more sense.

Also 517.13, the section that requires "redundant grounding" in general, only mentions branch circuits.[/QUOTE

TN, apparently knowing it's hard to teach old inspectors new tricks, is still in the "dark ages" of the '08 Code. (E) in '14 is (D) in '08 & '11.

 

[kwired]

Mike, I am confused. Are the feeders going to be serving patient care areas?

If so, the redundant grounding is required back to the panel as mentioned by kwired.

To make things a little more clear, the feeder doesn't serve the patient care areas the feeder supplies the branch circuits that supply patient care areas. It is possible for a feeder to serve only loads in the patient care area though. The redundant grounding requirements (more of a in the field term then a NEC term) is only for branch circuits serving patient care areas.

 

[kwired]

I think you meant 517.19(E) or hope you meant (E) because I read (D) several times and wondered if I was missing something, then I read (E) and things started making more sense.

Also 517.13, the section that requires "redundant grounding" in general, only mentions branch circuits.[/QUOTE

TN, apparently knowing it's hard to teach old inspectors new tricks, is still in the "dark ages" of the '08 Code. (E) in '14 is (D) in '08 & '11.

I see that (C) and entire content is marked as new or changed and only (D) and (E) are marked as changed but none of their content has changed except for three words in E are identified as changed from previous edition.

 

[mshields]

thanks for all the feedback

thanks for all the feedback

To answer your question George. The feeder is to a panel whose branch circuits serve patient care area's.

I guess the existing feeder is therefore ok since only branch circuits are indicated as having to have redundant grounding. Still, I would think the intent of the code, ostensibly to assure that the failure of one ground path does not result in NO ground path back to the source, would demand that the feeder to the panel have redundant paths as well.

Thanks,

Mike

 

[GoldDigger]

To answer your question George. The feeder is to a panel whose branch circuits serve patient care area's.

I guess the existing feeder is therefore ok since only branch circuits are indicated as having to have redundant grounding. Still, I would think the intent of the code, ostensibly to assure that the failure of one ground path does not result in NO ground path back to the source, would demand that the feeder to the panel have redundant paths as well.

Thanks,

Mike

IMHO the question that needs to be answered is whether the redundant ground is allowed to terminate at the sub panel or has to extend as a redundant path all the way back to the service panel.

 

[mshields]

the question

the question

that is my question?

 

[augie47]

I thought it was answered.... I may be incorrect in the answer but my read is that if it does not serve critical care no bonding/grounding beyond the conduit system is needed. If it serves critical care, bonding is need ed per 517.19 (*)
(* depends on Code cycle)

 

[kwired]

I thought it was answered.... I may be incorrect in the answer but my read is that if it does not serve critical care no bonding/grounding beyond the conduit system is needed. If it serves critical care, bonding is need ed per 517.19 (*)
(* depends on Code cycle)

I think you have the correct answer but to a different question

What I am seeing is 517.19(D/E depending on year) is about adding additional bonding to ensure continuity between raceway or cable sheath used as the only EG, sort of like how we have to add additional bonding or use something other then standard locknuts to ensure a metal service raceway is bonded. And this is only for feeders that serve critical care areas.

It still isn't requiring two separate grounding paths - metal raceway/metal sheath cable suitable for EGC plus a wire EGC inside, but rather is requiring additional step to make sure the allowed raceway only or cable sheath only EGC has low resistance connection through termination fittings to boxes, cabinets, etc.

This section only applies to feeders - the branch circuits to the critical area still need to have the "redundant" grounding as described in 517.13.

 

[kwired]

Still, I would think the intent of the code, ostensibly to assure that the failure of one ground path does not result in NO ground path back to the source, would demand that the feeder to the panel have redundant paths as well.

I think, and this is just my thoughts here, the intent of the "redundant" grounding path requried in 517.13 isn't for the sake of extra assurance of a path back to the source as much as it is to assure equipotential bonding to some extent. Sort of along same lines of why we bond everything conductive in and around swimming pools - to prevent any potential from existing between them. Doesn't matter as much if those items are sitting there at some potential above true earth, just matters that there is no potential to other objects the user or patient may come in contact with.