Slightly confused, seperate structure

[PlnOldRick]

i searched around and i dont know if its just a hard days work or what but i am still slightly confused about what i need to do in my case. story followed by questions, sorry, long..

so my boss calls me today to ask me a code question (thanks to this place!). we have a completely seperate structure. a garage with a mother in law on top of it. currently we have a 2 inch pipe run from the meter (common service for both structures) underground and under the slab of the structure stubbing up inside. he asked me if we need a disconnect at the meter. i asked him if he was planning on mounting a sub panel or a main breaker panel. he said a sub panel. i asked him if he had more then 6 circuits planned, he said yes. i told him to ditch the sub panel and install a main breaker panel to comply with the six disco rule (230.71). he didnt agree. am i right? from what i have read thus far i appear to be. also if we do install a mbp am i still required to install a disco at the meter. i cant find anything that say i would.

next i told him he also needed to drive a ground rod(or 2) according to 250.32 (A). he chattered on about no and how it is grounding the neutral in two different places and that the neutral is allready grounded back at the meter. then he reads is and say 250.32 (b) 1 says i dont have to. i told him (1) applies to you if you install a sub panel in the structure and pull an ecg with the feeders but never the less you still have to drive rods and connect it to the ecg. only thing it says is if you run an ecg with the feeders you do not bond the neutral.

i then told him since he NEEDS to just install a mbp to comply with the disco rule which would make that the first means of disconnect and also the fact that there is no ecg run with the feeders that (2) would apply to the situation and he would need to find a screwdriver and get himself a real purty green screw.

so am i confused or not? haha thanks for any comment.

btw 2002 cycle

[ December 05, 2005, 09:00 PM: Message edited by: PlnOldRick ]

 

[George Stolz]

Re: Slightly confused, seperate structure

Originally posted by PlnOldRick:
so my boss calls me today to ask me a code question (thanks to this place!).

Small world.

 

[PlnOldRick]

Re: Slightly confused, seperate structure

good so im not as confused as i initially thought. personally i told him he should just mount his main disconnect back at the meter for the exact reason you just said and then stick another disco or a main breaker in the panel at the seperate structure. easy enough since its a QO panel and can be converted blindfolded and hog tied but.... here at my company the "right" way takes a trunk ride to the profit margin.

also my apologies for typing ecg everywhere instead of EGC. i type with two fingers and things get a little hairy when i start pumpin out the words!

 

[George Stolz]

Re: Slightly confused, seperate structure

here at my company the "right" way takes a trunk ride to the profit margin.

Well, nothing like a tap on the shoulder from the codebook to get an MDP in the bid.

also my apologies for typing ecg everywhere...

I didn't notice that. I only noticed the mbp for MDP.

 

[George Stolz]

Re: Slightly confused, seperate structure

Then again, on closer review,

a garage with a mother in law on top of it.

This could constitute a violation of 230.40.

As it sits, you'd be using exception #3 to 230.40. But with a dwelling unit atop the garage, you are walking a fine line. Is the mother-in-law apt a dwelling unit?

Dwelling Unit. One or more rooms for the use of one or more persons as a housekeeping unit with space for eating, living, and sleeping, and permanent provisions for cooking and sanitation.

If it qualifies, I believe you'd need a disconnect at the house with the meter on it, in retrospect.

 

[mvannevel]

Re: Slightly confused, seperate structure

George, just curious as to why the Mother-in-law atop the garage would run him afoul of 230.40? Exception #3 permits the separate structure to have a set of service entrance conductors run to it without mentioning whether or not the separate structure is used as, or contains, a dwelling unit.

I'm seeing 3 options for him here. First a set of service entrance conductors run from the meter on the house with a main breaker panel in the garage. Second an outside tap from the house feeder as allowed in 240.21(B)(5). This would also require a main breaker panel in the garage. The third option would be to install a disconnect at the main structure and make the run to the garage a feeder and install a main breaker panel in the garage. Options 2 and 3 seem the most attractive since they provide ground fault and short circuit protection for the conductors. If service entrance conductors are run to the separate structure, 250.50 will require the grounding electrode system, or if a feeder or feeder tap supplies the structure, then 250.32(A) will require the grounding electrode system.

 

[raider1]

Re: Slightly confused, seperate structure

On a side note, it might make the holidays happier if you get the mother-in-law off the top of the garage.

(just couldn't help myself.)

Chris

 

[PlnOldRick]

Re: Slightly confused, seperate structure

figure i would update younz.

restarted the argument with the boss today. finally i got him to call the inspector for the area and talk to him. all i am going to say is my boss, while being almost 300 lbs feels somewhat smaller this evening.

oh and george sorry about the mbp instead of mdp im just so used to my trade slang of main breaker panel it filters into my abbreviations..

 

[electricmanscott]

Re: Slightly confused, seperate structure

Originally posted by raider1:
On a side note, it might make the holidays happier if you get the mother-in-law off the top of the garage.

(just couldn't help myself.)

Chris

Ah yeah, or leave her there.

 

[George Stolz]

Re: Slightly confused, seperate structure

Originally posted by mvannevel:
George, just curious as to why the Mother-in-law atop the garage would run him afoul of 230.40?

It's not explicit, but I could see an inspector rightfully asserting that none of the exceptions say it's okay to supply two dwelling units with one set of SE conductors. The exceptions mention dwelling units specifically and unabashedly, and none of those fit the bill for this installation.

Just because the structure's main function is a garage, it doesn't negate the fact that it is a dwelling unit. Is a house a single-family dwelling with an attached garage, or a garage with a dwelling unit attached to it? The NEC sees a single-family dwelling.

 

[allenwayne]

Re: Slightly confused, seperate structure

We did a large series of town homes near Tampa some had a granny flat as we spoke of.They were connected by a covered breezway,so 1 structure.
So the ones without a granny flat got a single meter while those with a granny flat got 1 2 bank meter 1 back to backed and the second was a disc to the mlo panel in the main structure.So p off granny and you had no power

 

[mvannevel]

Re: Slightly confused, seperate structure

Originally posted by georgestolz:
It's not explicit, but I could see an inspector rightfully asserting that none of the exceptions say it's okay to supply two dwelling units with one set of SE conductors. The exceptions mention dwelling units specifically and unabashedly, and none of those fit the bill for this installation.

I see your point that it's not explicit and that some inspectors might make that interpretation, but nowhere in 230.40 is it prohibited. The code is mute in exception #3 as to what that separate structure is. All we've done is modify the main rule that prohibits service drops or laterals from supplying more than one set of SE conductors. Remember, this isn't one set of SE conductors it's two. Exception #3 allows a set of SE conductors to be run to each structure from a single service drop or lateral. The reason for spelling out single-family dwelling unit in this exception is so that you couldn't do this if it were a commercial building and you were running a set of SE conductors to a separate structure on the same property from the same service drop or lateral. In that instance, you would need either a feeder or separate service.

The only real consideration here, as far as the separate structure being a dwelling unit, would be that the disconnecting means would need to be rated 100 amperes per 230.79(C).

 

[George Stolz]

Re: Slightly confused, seperate structure

Originally posted by mvannevel:
I see your point that it's not explicit and that some inspectors might make that interpretation, but nowhere in 230.40 is it prohibited.

Sure it is, 230.40 itself prohibits it, the exceptions start opening holes for specific circumstances. If the circumstances don't describe the situation at hand, we can't use the exception.

The code is mute in exception #3 as to what that separate structure is.

True, but exceptions 3 and 4 do use specific terminology regarding "single family, two-family, and multifamily" dwellings, as they relate to the main rule. It's a cakewalk to say that if the writers had intended to be able to supply two single-family dwellings off one drop, they would have specifically permitted it. They were too specific in the writing of #4 to say that they might have accidentally omitted it, IMO.

It would be a darn hard sell. And I specialize in hard sells.

 

[iwire]

Re: Slightly confused, seperate structure

George are you saying separate structure can not be a another dwelling unit?

A dwelling unit is always a structure.

Heck almost everything is a structure to the NEC.

 

[George Stolz]

Re: Slightly confused, seperate structure

A dwelling unit is a structure, sure.

I just think that if you apply some context to it, it doesn't make sense that you could supply a house and a 40 story skyscraper from the same drop. It's pretty much a given (IMO) that the "seperate structure" is a "sub-dwelling unit structure".

Replace the dinky garage with a ma-in-law with a 40 story skyscraper. It's a seperate structure too, but now that exception makes next to no sense, right?

Since the single-family dwelling unit is the prime structure of the exception, it follows that the seperate structure is not of that stature.

Hey, we can read it however we'd like. Technically, we can go nuts with this puppy. But when we try to apply this in the real world, there's going to be someone with a clipboard who'd need to be convinced that the installer wasn't criminally insane. And if everything rested on this, I believe a red tag would be soon to follow. Not the kind hanging from Bowtie-embossed mirrors across the nation, either.

 

[iwire]

Re: Slightly confused, seperate structure

Originally posted by georgestolz:
A dwelling unit is a structure, sure.

Yes.

Originally posted by georgestolz:
I just think that if you apply some context to it, it doesn't make sense that you could supply a house and a 40 story skyscraper from the same drop.

What problem would that pose to the NEC?

Why would that be safety issue?

Obviously cost issues will keep that from happening regardless.

Originally posted by georgestolz:
It's pretty much a given (IMO) that the "separate structure" is a "sub-dwelling unit structure".

Say what?

What is a "sub-dwelling unit structure"?

Now who is 'making up code'?

Originally posted by georgestolz:
Since the single-family dwelling unit is the prime structure of the exception, it follows that the separate structure is not of that stature.

I have no idea why you feel that way.

The code is what is written not what we may feel makes sense.

Originally posted by georgestolz:
I believe a red tag would be soon to follow. Not the kind hanging from Bowtie-embossed mirrors across the nation, either.

The inspector giving that tag would be wrong.

A modest house I worked at had a very large garage fed from the house, in that garage the family ran a Wrought Iron Railing business.

The electrical needs of the garage where much more than the needs of the house it was fed from.

Would you feel this deserves a red tag?

 

[mvannevel]

Re: Slightly confused, seperate structure

230.40 Merely prohibits a service drop or service lateral from supplying more than one set of service entrance conductors. The exceptions then list the situations where more than one set of service entrance conductors can be supplied from a drop or lateral:

Exception 1 permits it for services of different characteristics.

Exception 2 permits it where you have 2 to 6 disconnecting means grouped at one location.

Exception 3 permits it to supply a single family dwelling unit and a separate structure.

Exception 4 permits it to supply a house panel for 2 family or multifamily dwellings.

Exception 5 permits it for taps for load management and solar photovoltaic systems.

If the circumstances don't describe the situation at hand, we can't use the exception.

In this instance, the circumstances exactly describe the situation we have. We have a single family home and a garage, each supplied with a set of service entrance conductors from the same service drop. The exact wording of the exception says:

Exception No. 3: A single-family dwelling unit and a separate structure shall be permitted to have one set of service-entrance conductors run to each from a single service drop or lateral.

The fact that the garage contains living quarters has no bearing on this article. There is no mention of what the separate structure can or can't be. The only reason for mentioning single-family dwelling units at all is to limit the use of this exception to single-family properties. In other words you couldn't use this exception if you had, for example, a restaurant and separate structure. Exception #2, however, could be used for that application. Remember George, we're only talking about the number of sets of service entrance conductors that can be supplied by a single service drop or lateral.

It's a cakewalk to say that if the writers had intended to be able to supply two single-family dwellings off one drop, they would have specifically permitted it. They were too specific in the writing of #4 to say that they might have accidentally omitted it, IMO.

They'd have had to get a lot more specific to include all that separate structure could mean. Guest house, garage, pole barn, pool house, rec-room, greenhouse, storage shed, gate house, weight room, workshop, tractor barn, and on and on it could go. What that structure is called or used for is not within the scope of 230.40 or Part IV of section 230. It deals specifically with service-entrance conductors.