Power to Garage

[LarryFine]

Re: Power to Garage

I'll jump in the fray!

To respond to JW:

1) Sounds like a feeder to me, according to this definition.

2) Obviously, the existence of breakers determines branch circuit or feeder.

3) Yes, as suggested here:

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.

 

[jwelectric]

Re: Power to Garage

Again the confusion starts.

The disconnecting means that is located at the detached garage is as outlined in the original post:

Garage has a MLO panelboard with 6 breakers (2-Two Pole & 4-Single Pole)
Is a disconnect required at the garage ahead of the panelboard?

He has fulfilled this requirement as outlined in:

225.33 Maximum Number of Disconnects.
(A) General. The disconnecting means for each supply permitted by 225.30 shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be no more than six disconnects per supply grouped in any one location.

I think where the confusion comes is that no one knows just what a disconnecting means is:

Article 100 Disconnecting Means. A device, or group of devices, or other means by which the conductors of a circuit can be disconnected from their source of supply.

I hear that the disconnect needs to be rated at ?? amperes but I find no where that this disconnecting means is required to be a single unit.

By definition it can be a group of devices.

Take a close look at 230.79. Is this disconnecting means required to be a single pull of the hand? The wording is the same.

As for a single branch circuit needing a disconnecting means I will need to ponder for a while but as I think now I say no.

 

[iwire]

Re: Power to Garage

I am still unsure if the 225.39 rating requirements can be met with the combined rating of a group of switches.

Mike you make a great argument for it, and I think it also makes sense.

The one problem I have is 230.80.

230.80 Combined Rating of Disconnects.
Where the service disconnecting means consists of more than one switch or circuit breaker, as permitted by 230.71, the combined ratings of all the switches or circuit breakers used shall not be less than the rating required by 230.79.

Why was 230.80 needed if the combined rating is already allowed?

Why is there not a similar section in 225?

Bob

 

[mvannevel]

Re: Power to Garage

Originally posted by iwire:
I am still unsure if the 225.39 rating requirements can be met with the combined rating of a group of switches.

Mike you make a great argument for it, and I think it also makes sense.

The one problem I have is 230.80.

230.80 Combined Rating of Disconnects.
Where the service disconnecting means consists of more than one switch or circuit breaker, as permitted by 230.71, the combined ratings of all the switches or circuit breakers used shall not be less than the rating required by 230.79.

Why was 230.80 needed if the combined rating is already allowed?

Why is there not a similar section in 225?

Bob

230.71 gives us permission to use a maximum of six breakers or switches as the service disconnecting means but makes no mention of a requirement for a combined rating. That's why 230.80 is necessary, so that this combined rating is required rather than allowed.

Why is there not a similar section in 225?

Because we're talking about a feeder here rather than a service. We already have overcurrent protection ahead of the feeder conductors. I don't think omitting the requirements of 230.80 in Article 225 was an oversight. In the example I gave above, there is already a 60 ampere breaker in the house for the garage feeder. What would be gained by the breakers in the garage panel adding up to 60 amperes? The important thing here is that the enclosure is rated at least 60 amperes and the structure can be disconnected with six or fewer swipes of the hand. What if, in my example, I had run a 40 ampere feeder to the panel in the garage? Nothing says that I can't, as long as it's adequate to serve the load and the enclosure for the disconnecting means is rated at least 60 amperes.

 

[charlie b]

Re: Power to Garage

Let me cut to the bottom line. A detached structure has to have a disconnecting means of its own. The breaker from the other building (i.e., protecting the feeder) does not count. That disconnecting means must be rated at least 60 amps. If the disconnecting means consists of an MLO panel with not more than 6 breakers, then how do we achieve the "must be rated at least 60 amps" requirement?

In this issue, I think we should not take sides and argue about "it says this" or "it means that." The bottom line is this: It's badly written. It needs to be revised. Anyone want to take on the authorship? Time is running short for the 2008 NEC.

 

[jwelectric]

Re: Power to Garage

Originally posted by jwelectric:

As for a single branch circuit needing a disconnecting means I will need to ponder for a while but as I think now I say no.

The question has arisen as to weather a single circuit supplying a receptacle at a second building or structure will require a disconnecting means.

My answer is No!

Does a twist lock located at a swimming pool require a disconnecting means?
Will the 125 volt 15 or 20 amp receptacle that is required with-in 20 feet require a disconnecting means?
Would a duplex receptacle located at the bottom of a sign require a disconnecting means?
Will a duplex at the bottom of a pole lamp require a disconnecting means?

The answer to all of the above can be found in the function of the receptacle itself.
Just what is a receptacle?

Could a receptacle be a means of disconnect? Should you answer this question with a yes then you have answered the question, does a receptacle at a second building or structure require a disconnecting means. The disconnecting means is already there in the receptacle itself!
I shall now quit pondering this question.

 

[George Stolz]

Re: Power to Garage

Originally posted by charlie b:
Anyone want to take on the authorship? Time is running short for the 2008 NEC.

I shall attempt to slay the dragon, my liege.

 

[George Stolz]

Re: Power to Garage

I fiddled, I poked at it, and ultimately decided it just didn't taste right.

Toss it.