ground rods at a townhouse

[pierre]

Re: ground rods at a townhouse

In the discussion of occupancy, they are not talking about the building being occupied, they are talking about the type of occupancy. Such as a multiuse building of say; a pizza place that needs 3 phase on the first floor and apartments upstairs that only need single phase.

Pierre

 

[earlydean]

Re: ground rods at a townhouse

Guys,
Exactly my point. 230.2 won't allow multiple services of the same voltage, phases, frequencies, etc. except to separate buildings.
And, if there are multiple services to one structure (Townhouse) then each service needs individual supplemental grounding (rods). Not supplemental grounding at a central point for all buildings.

Earl

 

[don_resqcapt19]

Re: ground rods at a townhouse

Just because we have a single "service" doesn't mean that we can't have multiple sets of "service entrance cables" and multiple remote service disconnects. I don't read the word "occupancy" in exception 1 to 230.40 as applying to "types of occupancy". I believe it is a more general usage and each utility customer is permitted to have his own set of service entrance cables and his own service disconnect.
The connection of the GEC from the water pipe to the grounded conductor of the serivce disconnect meets the requirements of 250.24(A)(1) and 250.24(C). The connection of the supplemental GEC to the grounded conductor at the meter meets the requirements of 250.53(D)(2).
Don

 

[eprice]

Re: ground rods at a townhouse

The point that Pierre brings up about the meaning of "occupancy" is something that I had thought about when I first saw this thread. The term is not difined in the NEC. As Pierre points out, if we were using that term the way it is used in the building code, then in the scenario we are discussing, there would be only one "occupancy", ie. R-3 (In IBC land), but the building code definition is not referenced by the NEC, and it is not clear to me that the building code definition is what the writers of the NEC were thinking when they wrote section 230.4 nor is it clear to me that that definition is the one that makes the most sense here.

 

[earlydean]

Re: ground rods at a townhouse

I take exception to the term multiple remote disconnects. Disconnects must be grouped together by 230.71

Just because we have a single "service" doesn't mean that we can't have multiple sets of "service entrance cables" and multiple remote service disconnects.

Yes?, NO?

Earl

 

[don_resqcapt19]

Re: ground rods at a townhouse

Earl,
230.71(A) permits each set of service conductors to have 1 to 6 disconnects. 230.70(A)(1) requires that these disconnects be located "nearest the point of entrance of the service conductors". There is no code requirement that the disconnects for each of the sets of service entrance conductors be grouped with the disconnects for the other sets of service entrance conductors. The only requirement is that the 2 to 6 disconnects permitted for a single set of service entrance conductors be grouped with the other disconnects for that set of service entrance conductors.
Don

 

[earlydean]

Re: ground rods at a townhouse

Thanks for the info, Don. I see I was in error all these years. Although, I haven't run into this sort of thing very often. Thanks again,

Earl

 

[pierre]

Re: ground rods at a townhouse

Don

I am not trying to be a smart^$$ here, but I am reading the same NEC as you and do not read it the same.

230.72 Grouping of Disconnects.
(A) General. The two to six disconnects as permitted in Section 230.71 shall be grouped. (NEC)

In an apartment building, there is usually a disconnect ahead of the meters, and then the panels/disconnects to the apartments are feeders.
There usually are no firewalls between the apartments.

In smaller buildings, such as in this example, the firewalls define the units as separate buildings, and therefore the panels are run to each unit as a service, not feeders.

Grouping of services on one building are not necessarily required, depending on circumstances.

Pierre

[ September 27, 2003, 06:52 PM: Message edited by: pierre ]

 

[pierre]

Re: ground rods at a townhouse

I am not an NFPA representative, but I believe that the term 'occupancy' here is in reference to the type of occupancy, not the fact the building is occupied. This again is my understanding of the term.

Pierre

 

[don_resqcapt19]

Re: ground rods at a townhouse

Pierre,

I am not trying to be a smart^$$ here, but I am reading the same NEC as you and do not read it the same.

That just happens to be a problem anytime we write rules and different people read those written rules.

Prior to the '99 code the exception in question was worded as follows: "Buildings with more than one occupancy shall be permitted to have one set of service entrance conductors run to each occupancy or group of occupancies." In the '99 code the wording was changed to permit one set of service entrance conductors for each class of service run to each occupancy.(proposal 4-93 in the 98 ROC). The substantiation was to permit additional sets of service entrance cables to serve an occupancy that requires more than one class of service. Also look at the submitters statement on proposal 4-95. It appears to me that the intent is to permit each utility customer to have his own set of service entrance conductors and service disconnects fed from a common service drop or lateral. This is even more clear to me when reading the '96 wording.
Don

[ September 27, 2003, 09:39 PM: Message edited by: don_resqcapt19 ]

 

[earlydean]

Re: ground rods at a townhouse

"Occupancy" in building code refers to the type of use of the building. Such as a mercantile , educational, residential, etc. types of occupancies. The risk to the occupants is greater for some types of occupancies than others. The building code will then stipulate rules for construction components and details based upon the concept of "equivalent risk", Trying to lessen the hazards of who is in a building and what goes on in a building by fire alarms or suppression systems, wider hallways and egress doors, or walls, floors and ceilings that resist fire to greater degrees.

 

[don_resqcapt19]

Re: ground rods at a townhouse

Earl,
I don't agree that is the meaning of "occupancy" in this code section. If you read the ROPs and ROCs, it is clear to me that the code panel intends to permit each power company customer to have his own set of service entrance cables.
Don

 

[earlydean]

Re: ground rods at a townhouse

Don,
That is the trouble with using the definition from one code with the use of the term in another code. (And ICC and NFPA are not even on speaking terms.) Are you are saying that, in the NEC, occupancy means whomever is occupying the building?(or part of a building) Therefore, every apartment is a separate occupancy, every store in a strip mall is a separate occupancy and every room of a rooming house is a separate occupancy because they are occupied by different persons?
Earl

 

[don_resqcapt19]

Re: ground rods at a townhouse

Earl,
Acutally it appears that the NEC uses the term both ways. In most cases the word is used as you have defined it, but in a few it is used differently. Look at 225.35, 230.72(C), 240.24(B), and 250.104(A)(2). In these cases and in the case of Exception #1 to 230.40(at least in my opinion) the word applies to each unit and not the usage of the building or portion of the building. In rest of the code the same word applies to the usage of the building.
Don

 

[earlydean]

Re: ground rods at a townhouse

Also 230.2(B). I see the error of my ways.

Thanks

 

[hurk27]

Re: ground rods at a townhouse

By Don

posted September 23, 2003 03:37 PM
--------------------------------------------------------------------------------
Earl,
I read the exception to 230.40 as saying each occupancy is permitted to have one service for each type of service that the occupancy requires. In this case each occupancy only requires one type of service, so each occupancy is permitted to have one set of service entrance conductors fed by a common service drop or lateral.
Don

Then where would exception 2 (230.40) would of ever been needed? as it only allows this if there is disconnects installed and they are grouped together.
Wasn't this requirement for the fact that emergency personnel being able to turn off power for safety?
And for Dean how are these service entrance cables ran outside the buildings to allow for no protection of the entrance cables in the event of them shorting out. as even conduit by it self would not prevent the arc from igniting a wood wall if they are ran across the back of the building?

 

[don_resqcapt19]

Re: ground rods at a townhouse

hurk,
I have no idea why Exception #2 is in the code. 230.71(A) permits each set of service entrance conductors to have up to six disconnect switches.
Don

 

[hurk27]

Re: ground rods at a townhouse

Don I'm not trying to be argumentative, Just trying to understand why if some things are allowed,then in another exciption it only allows it a certain way, There is several instance of this in the code.

 

[don_resqcapt19]

Re: ground rods at a townhouse

Exceptions are not supposed to be restrictive to other sections of the code. They are only permitted to modify the section that they are attached to.
Don

 

[earlydean]

Re: ground rods at a townhouse

It seems to me that 230.40 should be re-written. Instead of making the statement that only one set of service-entrance conductors are allowed per service drop or lateral, then listing 5 exceptions, it should say as many sets of service-entrance conductors may be connected to each service drop or lateral as is considered necessary by the installing electrician, or the design engineer. The only limits would be the ampacity of the conductors to be sufficient for the computed loads.

There is no overcurrent or short-circuit protection on the utility side of service conductors anyway. that is why they must be outside the building, and terminate in a disconnect and OC device immediately upon entry into the building.

Earl