Disconnecting Means: ?Service Entrance Rated??

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charlie b

charlie b

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I?m designing a facility that will have a diesel generator as a back up source. There will be an ATS for ?Life Safety? loads (egress lights), and a separate ATS for ?Optional Standby? loads. 230.2(A)(2) and (4) allow me to use this DG as a second service (in my case, second and third service) to the building. The specifications for the DG set will require two, separate, local disconnecting means. They will be accessible, and within sight of the building. Per 700.12(B)(6), I don?t plan on placing another pair of disconnects at the point at which the DG?s conductors enter the building. Two questions:
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  • <font size="2" face="Verdana, Helvetica, sans-serif">Are the two local disconnects at the DG required to be ?Service Entrance Rated??</font>
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  • <font size="2" face="Verdana, Helvetica, sans-serif">Is it unusual to require the DG vendors to provide ?Service Entrance Rated? local disconnects (i.e., is this not their standard product)?</font>
<font size="2" face="Verdana, Helvetica, sans-serif">The only place I?ve seen in which a disconnect is required to be ?Service Entrance Rated? is in 225.36. But that does not apply, as there is only one building.
 
Re: Disconnecting Means: ?Service Entrance Rated??

Charlie, you only have one service to the building, definitions art 100. The two feeds from the gen set are either in the building or not, and if not in the building are indeed covered by art 225. Also, the exception for not having a disconnect in the building if the disconnect for the generator is in within sight only applys to art 700 and 701, not to the optional standby system.

Fred Bender
 
Re: Disconnecting Means: ?Service Entrance Rated??

Charlie,

Is the DG inside of the building that houses the ats trasfer switches?

Jim
 
Re: Disconnecting Means: ?Service Entrance Rated??

The DG will be pad-mounted outside the building. The ATS devices are both in the Main Electrical Room (i.e., same room as the Main Service Panel).

Originally posted by derf48: The two feeds from the gen set . . . (if not in the building) are indeed covered by art 225.
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I don?t see that. The first sentence of 225 says that the article applies to feeders run between buildings or structures. I don?t think a pad-mounted gen set is a ?structure,? and it is certainly not a building. But if you are right, then the disconnects that come with the gen set would have to be ?Service Entrance Rated,? per 225.36.

Any other opinions on this part of the issue?
Originally posted by derf48: Also, the exception for not having a disconnect in the building if the disconnect for the generator is in within sight only applies to art 700 and 701, not to the optional standby system.
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It?s not an ?exception,? it is a permissive statement. But I see you are right, in that it does not appear in 702.

Is there some other statement in the code that would tell me I need a disconnect at the side of the building? If the power from the DG is a ?service,? and there seems to be some room for discussion on that point, then 230.70 would require a disconnecting means. This is in Washington State, so by a WAC (local rule) the local disconnects would not count, if they are more than 15 feet from the building (the NEC would have allowed 50 feet). But I don?t think this applies, at least to the disconnect that feeds the Article 700 loads.

Any other opinions on this part of the issue?
 
Re: Disconnecting Means: ?Service Entrance Rated??

Charlie B.:

I don't think the generator is a service either. See the definition of service in Article 100:

Service: The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.

Steve
 
Re: Disconnecting Means: ?Service Entrance Rated??

I think 225 does apply. If you read the first paragraph a little farther:

...feeders ran on or between buildings...; and electric equipment and wiring.....

That's one heck of a paragraph, but I think it includes wiring between buildings and electric equipment.

I think "suitable for service equipment" basically means it is safe to connect it to a feeder or supply that doesn't have overcurrent protection. For example, a service equipment may be connected to the secondary of a utility transformer that doesn't have any secondary OCP.

I don't think this is necessary for your generators. The disconnect and generator are probably listed together as a unit by UL or another underwriter.

Steve
 
Re: Disconnecting Means: ?Service Entrance Rated??

Originally posted by steve66: I think 225 does apply. If you read the first paragraph a little farther: ...feeders ran on or between buildings...; and electric equipment and wiring.....

That's one heck of a paragraph, but I think it includes wiring between buildings and electric equipment.
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For the moment at least, I am going to contend that 225 does not apply, for the simple reason that I would rather it not apply. ;)

Please consider the following phrase:
This rule applies to A and B.
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The word ?and? within this phrase allows us to rearrange the phrase as follows:
This rule applies to A.

and

This rule applies to B.
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Now go back and re-read the first paragraph of 225. If I leave out some of the ?this and that and the other also? words and phrases unrelated to my facility, I believe it is saying,
This rule applies to feeders run between buildings.

and

This rule applies to electric equipment and wiring that is attached to the outside of buildings.
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I conclude that 225 does not cover the wiring between outdoor equipment and the building. I believe that the words you quoted are intended to address such things as a breaker from an indoor panel supplying power to a sign that is attached to the side of the building.
 
Re: Disconnecting Means: ?Service Entrance Rated??

CharlieB,
I think you are streeeeeching the 230.2(A) a bit more than most.The question ,first is,Is the gen. a service? Where are the service entrance conductors.IMO emergency systems,and optional standby systems alone,not a service do they make.

frank
 
Re: Disconnecting Means: ?Service Entrance Rated??

i would say it would be according if this is a SDS or a nonSDS
 
Re: Disconnecting Means: ?Service Entrance Rated??

Charlie b...The 2005NEC allows a disconnect at the generator set under 702.11 for the optional standby supply...

90.3 states that chapters 5, 6, and 7 modify the general rules of chapters 1, 2, 3, and 4. So, I would say that the you are required to design your systems according to the applicable rules of article 700, 701, and 702

700.12(B)(6), 701.11(B)(5), and the new for 2005 702.11 all say an addition disconnect shall not be required where located "within sight" of the building.

shortcircuit2
 
Re: Disconnecting Means: ?Service Entrance Rated??

Originally posted by benaround: CharlieB, I think you are streeeeeching the 230.2(A) a bit more than most. The question ,first is, ?Is the gen. a service??
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Is it me who is doing the stretching? I would prefer that the generator conductors not be considered ?services.? But look at 230.2, and then at 230.2(A): They say that you can only have one service to a building, unless it is one of the following situations. Then it appears to include 700, 701, and 702 in the list. Or is it?

As some have pointed out, the definition of ?service? requires the participation of a ?utility.? Is 230.2 saying that you can have the utility company provide one service for the normal loads, a second service for emergency loads, and additional services for standby loads? Do I conclude that if I were to choose to use a DG for the ?emergency loads,? and choose not have the utility provide a second transformer, then I am not adding a second ?service,? as allowed by 230.2(A)?
 
Re: Disconnecting Means: ?Service Entrance Rated??

Charlie b,
That's the way I have always looked at it,and I think that is the intent.
Anyone feel diferently on this matter????

frank
 
Re: Disconnecting Means: ?Service Entrance Rated??

Charlie
There are some buildings that have more than one UTILITY service to the premises. The emergency service will be an actual 2nd utility provided service (it might even be from a different grid), not a generator provided supply.

A generator supply to an emergency or optional standby system will not be considered a second service to the premises, it is a backup system.
As has been stated, the NEC changed the definition of SERVICE a few years ago using the phrase "from the serving utility".


225.1 Scope. This article covers requirements for outside branch circuits and feeders run on or between buildings, structures, or poles on the premises; and electric equipment and wiring for the supply of utilization equipment that is located on or attached to the outside of buildings , structures, or poles.

700.12(B)(6)
(6) Outdoor Generator Sets. Where an outdoor housed generator set is equipped with a readily accessible disconnecting means located within sight of the building or structure supplied, an additional disconnecting means shall not
be required where ungrounded conductors pass through the building or structure.


insight from and no more than 50 feet.
 
Re: Disconnecting Means: ?Service Entrance Rated??

Charlie b,
I would also agree that you are not adding a second "Service" with the installation of the diesel generator as the supply system for your "Life Safety"loads and "Optional Standby" loads.

But, IMO your are required to install a disconnect at the building served by the DG suitable for use as service equipment per 225.36 because the feeder to the building from the DG originates from the gen set which is mounted on a structure (the concrete pad).

Now, if the gen set is within sight of the building, then the disconnect at the generator would be all that is required by 701.11(B)(5) or 702.11 2005 NEC

shortcircuit2
 
Re: Disconnecting Means: ?Service Entrance Rated??

You are not adding a service, you are just providing an backup service from your DG. It is considered a service, but the two are not operational at the same time. It is my opinion and the opinion of my AHJ that you have only 1 service.
 
Re: Disconnecting Means: ?Service Entrance Rated??

Furthermore, I wholeheartedly agree with short circuit, I just don't feel like rewriting it. So ditto. :D
 
shortcircuit2 said:
Charlie b,
I would also agree that you are not adding a second "Service" with the installation of the diesel generator as the supply system for your "Life Safety"loads and "Optional Standby" loads.

But, IMO your are required to install a disconnect at the building served by the DG suitable for use as service equipment per 225.36 because the feeder to the building from the DG originates from the gen set which is mounted on a structure (the concrete pad).

Now, if the gen set is within sight of the building, then the disconnect at the generator would be all that is required by 701.11(B)(5) or 702.11 2005 NEC

shortcircuit2
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Why does 700.12.B.6 even exist? It is responding to something - what?

If the generator is not a service and if 225.36 does not apply, then why do we need an exception. You don't need an exception if there wasn't something to except.

When is a disconnect required? The disconnect on a commercial generator is almost never 'in sight'. It is locked up in an enclosure, which means it is only readily accessible to the person with the key.
 
dema: Did you happen to notice that this thread is over a year old? :eek:

I no longer work for the same company, and I don't know how that project turned out. So I, at least, no longer have an interest in discussing that question. Anyone else is welcome to participate.
 
If you have the handbook, and if you look under the definition of "accessible-readily", the commentary says something can be behind a locked door and still be considered readily accessible. As long as the people who need access have access to the key.

I would also consider "locked in an enclosure" as within sight if the enclosure is within sight. However, that is only an opinion. Others will probably see it differently.

STeve
 
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