Separate Structure made of steel

[Dennis Alwon]

I have a home with a 200 amp service where they are building a detached carport made almost entirely of steel. I ran a 12/3 to the structure. I know I do not need a ground rod however do I need to bond the building steel. If yes, can it be the EGC or must I bond it back to the panel with a #4 copper?

 

[mcclary's electrical]

I have a home with a 200 amp service where they are building a detached carport made almost entirely of steel. I ran a 12/3 to the structure. I know I do not need a ground rod however do I need to bond the building steel. If yes, can it be the EGC or must I bond it back to the panel with a #4 copper?

IMO, you do need the ground rod. And I would bond building steel to EGC and electrode.

 

[Dennis Alwon]

IMO, you do need the ground rod. And I would bond building steel to EGC and electrode.

Read 250.32 exception

250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).
(A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250. The grounding electrode conductor(s) shall be connected in accordance with 250.32(B) or (C). Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed.
Exception: A grounding electrode shall not be required where only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the normally non?current-carrying metal parts of equipment.

 

[SEO]

Dennis using the exception to 250.32(A) it looks like you could use the equipment grounding conductor to ground the steel. The exception says for grounding the normally non-current-carring metal parts of equipment. The building is not really equipment but I think that the intent is ment. And also per the exception a grounding electrode is not required in your situation.

 

[Dennis Alwon]

Dennis using the exception to 250.32(A) it looks like you could use the equipment grounding conductor to ground the steel. The exception says for grounding the normally non-current-carring metal parts of equipment. The building is not really equipment but I think that the intent is ment. And also per the exception a grounding electrode is not required in your situation.

Okay I don't need a GEC but what about bonding the steel. Also, if the steel is an electrode then we must use all available. ????

 

[SEO]

If you use the exception a grounding electrode is not required. Bonding the steel to the equipment grounding conductor would add protection.

 

[raider1]

Dennis, this is a very good question.

250.104(C) requires that exposed structural metal that is not intentionally grounded and is likely to become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor or the grounding electrodes used. This also requires that the bonding jumper used to connect the building metal be sized in accordance with 250.66 and installed in accordance with 250.64(A),(B), and (E).

This section does not really address a detached structure.

IMHO, the easiest way to comply with this section is to intentionally ground the metal by connecting it to 2 ground rods.

Chris

 

[Jim W in Tampa]

Dennis, this is a very good question.

250.104(C) requires that exposed structural metal that is not intentionally grounded and is likely to become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor or the grounding electrodes used. This also requires that the bonding jumper used to connect the building metal be sized in accordance with 250.66 and installed in accordance with 250.64(A),(B), and (E).

This section does not really address a detached structure.

IMHO, the easiest way to comply with this section is to intentionally ground the metal by connecting it to 2 ground rods.

Chris

Is no need for the 2 rods and actually could create a hazard should the house ever loose a nutral.

While not required i would bond the steel to the branch circuit, perhap by screwing any steel boxes that are part of your install to the structure.

 

[Dennis Alwon]

While not required i would bond the steel to the branch circuit, perhap by screwing any steel boxes that are part of your install to the structure.

This is what I was going to do but the inspection department wants a #4 back to the panel. I can't seem to argue it well enough to make my point.

 

[raider1]

Is no need for the 2 rods and actually could create a hazard should the house ever loose a nutral.

By installing 2 ground rods and connecting them to the building steel, you have now intentionally grounded the steel so that 250.104 no longer applies.

While not required i would bond the steel to the branch circuit, perhap by screwing any steel boxes that are part of your install to the structure.

250.104(C) requires that exposed structural metal of a building that is likely to become energized and not intentionally grounded be bonded.

Chris

 

[raider1]

This is what I was going to do but the inspection department wants a #4 back to the panel. I can't seem to argue it well enough to make my point.

Dennis, it sounds like they are citing 250.104(C) is that correct?

Chris

 

[Jim W in Tampa]

This is what I was going to do but the inspection department wants a #4 back to the panel. I can't seem to argue it well enough to make my point.

Ask them how this is any differant than metal studs in a house or building. We don't run #4 to them and they do stand a chance of being energized. All they get is the same ground that your boxes get. What is reasoning behind #4 if circuit in carport is #!2. The fault would be cleared by the branch circuit.
I would ask for the code # they are applying. My feeling is you have intentially grounded it thru the branch circuit by way of steel boxes.

 

[Pierre C Belarge]

I have a home with a 200 amp service where they are building a detached carport made almost entirely of steel. I ran a 12/3 to the structure. I know I do not need a ground rod however do I need to bond the building steel. If yes, can it be the EGC or must I bond it back to the panel with a #4 copper?

I am not sure what wiring method you used to install the 12/3.
Why not use a metal bell box and mount the box so it is bonded to the metal structure of the carport?
The equipment ground conductor installed with the 12/3 meets the exception to 250.32(A). Case closed

 

[Dennis Alwon]

I am not sure what wiring method you used to install the 12/3.
Why not use a metal bell box and mount the box so it is bonded to the metal structure of the carport?
The equipment ground conductor installed with the 12/3 meets the exception to 250.32(A). Case closed

This is what I was going to do but they insist that the wire must be sized to 250.66 as Chris stated.

Chris- I believe that is the section cited but they never gave a reference. I should have asked.

Again 250.32 references grounding electrode. Suppose they just want it bonded whether it meets the requirements of an electrode or not.

 

[benaround]

I don't think you will find anywhere in the code a requirement to bring a GEC from a

seperate structure into the main ( or other ) building. If the 12/3 feed landed in a 2 circuit

disconnecting means, the steel and a ground rod would connect to the #12 EGC of the

feed. How far do your tutorial skills go ?

 

[Pierre C Belarge]

This is what I was going to do but they insist that the wire must be sized to 250.66 as Chris stated.

Chris- I believe that is the section cited but they never gave a reference. I should have asked.

Again 250.32 references grounding electrode. Suppose they just want it bonded whether it meets the requirements of an electrode or not.

From your description, this seems like a relatively simple structure.
There is one circuit installed. There is a code reference in the form of an exception that excludes the need for a GEC.
The second sentence of the exception permits the EGC of the branch circuit to provide the means for grounding.

I would point this out, as they may have missed this and are focused on some other code section.

 

[Dennis Alwon]

From your description, this seems like a relatively simple structure.
There is one circuit installed. There is a code reference in the form of an exception that excludes the need for a GEC.
The second sentence of the exception permits the EGC of the branch circuit to provide the means for grounding.

I would point this out, as they may have missed this and are focused on some other code section.

I don't think they are looking for a gec but just to bond the steel. I agree with you but now to convince them.

 

[benaround]

I don't think they are looking for a gec but just to bond the steel. .

In that case, the egc of the circuit that is likely to energize the steel is allowed to bond it.

 

[M. D.]

I don't think they are looking for a gec but just to bond the steel. I agree with you but now to convince them.

I'm not sure what to think :-? I found this in the 2010 rop . If I'm reading this correctly he wanted to get some relief from 250.66 ,. they killed that because he used sections that pertain to water pipes

I think he was after 250.122 sizing .. but they did add the disconnecting means for seperate structures but kept the 250.66 requirement ,... so a # 8 to your structure disconnect ??

Again this is the 2010 ROP but I hope it sheds some light ,.. looks like the inspector is partially right .. I think # 8

grey is what is proposed for deletion ,.. underline is proposed for new wording

5-254 Log #3527 NEC-P05 Final Action: Accept in Principle in Part
(250.104(C))
_______________________________________________________________
Submitter: Phil Simmons, Olympia, WA
Recommendation: Revise the existing text of the 2008 NEC as follows:

(C) Structural Metal. Exposed structural metal that is interconnected to form
a metal building frame and is not intentionally grounded or bonded and is
likely to become energized shall be bonded to the service equipment enclosure,
the grounded conductor at the service, the grounding electrode conductor if
where of sufficient size, or the one or more grounding electrodes used. The
bonding jumper(s) shall be sized in accordance with Table 250.66 except as
permitted in 250.104(A)(2) and (A)(3) and installed in accordance with
250.64(A), (B), and (E). The points of attachment of the bonding jumper(s)
shall be accessible unless installed in compliance with 250.68 Exception No. 2.

Substantiation: The phrase ?likely to become energized? is proposed for
deletion as most often, electrical inspectors enforce bonding of structural metal
if the building or structure has exposed metal members and the building or
structure is supplied with a service, feeder or branch circuit.
The reference to 250.104(A)(2) and (A)(3) will allow adjustment in the size
of bonding conductors and jumpers if the building s supplied by a feeder.
The reference to 250.68 Exception No. 2 permits the connection of bonding
conductors or jumpers to be fireproofed and not be accessible if appropriate.
Section 3.3.4 of the NEC Style Manual states that ?where? should not be used
to mean ?when? or ?if.? This proposal intends to use the word ?if? where
appropriate.

Panel Meeting Action: Accept in Principle in Part

Revise text to read as follows:

(C) Structural Metal. Exposed structural metal that is interconnected to form
a metal building frame and is not intentionally grounded or bonded and is
likely to become energized shall be bonded to the service equipment enclosure,
the grounded conductor at the service, the disconnecting means for buildings or
structures supplied by a feeder or branch circuit, the grounding electrode
conductor where if of sufficient size, or the one or more grounding electrodes
used.
The bonding jumper(s) shall be sized in accordance with Table 250.66
and installed in accordance with 250.64(A), (B), and (E). The points of
attachment of the bonding jumper(s) shall be accessible unless installed in
compliance with 250.68(A) Exception No. 2.

Panel Statement:
The panel does not accept the deletion of ?likely to become energized?. If the AHJ believes the structural metal is likely to become
energized then bonding is required. There is no reason to eliminate the
flexibility provided when situations occur involving structural metal that is
unlikely to become energized. The panel does not accept the recommendation
to refer to Sections 250.104(A)(2) and (A)(3) because these sections cover
bonding of metal water piping. The panel action on Proposal 5-253 has been
incorporated into the panel action on this proposal.
Number Eligible to Vote: 16
Ballot Results: Affirmative: 16

 

[tom baker]

There is an exception for dwelling units from having a grounding electrode were fed by a single or multiwire BC.
But you still have to comply with the disconnecting means requirement in 225
225.31 Disconnecting Means.
Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure.
225.32 Location.
The disconnecting means shall be installed either inside or outside of the building or structure served or where the conductors pass through the building or structure. The disconnecting means shall be at a readily accessible location nearest the point of entrance of the conductors. For the purposes of this section, the requirements in 230.6 shall be utilized.

225.36 Suitable for Service Equipment.
The disconnecting means specified in 225.31 shall be suitable for use as service equipment.
Exception: For garages and outbuildings on residential property, a snap switch or a set of 3-way or 4-way snap switches shall be permitted as the disconnecting means.