225.30 and prefab classrooms

[mvannevel]

David-
I know there are a lot of these around, hooked up just as you describe with 2 feeders run to them. I've run into them before, but never inspected one of them...until recently. Got one that's been moved in to be used as an office for a Christmas tree farm. This is a used unit that has been around the block and the approval stickers are still on it as proof (however none of them from Michigan). Frankly I've been confused about just how to handle this myself. I agree with the CMP members from your IAEI chapter, but only to a point. If we are limited to one feeder to these structures, that limit will come from 550 not 225.

However, 550.10(A) says: The power supply to the mobile home shall be a feeder assembly consisting of not more than one listed 50-ampere mobile home power-supply cord with an integrally molded or securely attached plug cap or a permanently installed feeder.

So now, I'm back to square one. That seems to say one supply whether it's a cord or a permanent feeder. Or, am I reading that wrong? I had intended to bring this up at our Metro Inspectors meeting last week and didn't. Hopefully I won't have to make a hard and fast decision until after the Western Section meeting next month.

It would be interesting to hear what CMP 19 has to say on the issue.

Maurie

 

[Smart $]

Let's say you have one building on a property with one service (pretty typical, eh?). You put one service disconnecting means on the outside of that building. How many feeders can you run off the load side of the service disconnecting means into the building?

...

Smart, in answer to your question, off the hip, I'd say infinute.

OK, we'll run with that...

550.4 General Requirements
(B) In Other Than Mobile Home Parks. Mobile homes installed in other than mobile home parks shall comply with the provisions of this article.​

Loosely interpretted because the mobile home is "in other than a mobile home park", when you anchor down and connect a mobile home, the spot on which the mobile home sits is a Mobile Home Lot.

550.2 Definitions
Mobile Home Lot. A designated portion of a mobile home park designed for the accommodation of one mobile home and its accessory buildings or structures for the exclusive use of its occupants.​

Because of the preceding...

550.2 Definitions
Mobile Home Park. A contiguous parcel of land that is used for the accomodation of occupied mobile homes.​

Hopefully your getting the gist of where this is going, so let's fast forward a bit, and rather than retyping these subparts I'll just provide the references and add notes as appropriate...

Power Supply, Feeder... 550.10(A x2) takes us to 550.32(B)... make note of the very last sentence, "Where service equipment is not installed in or on the unit, the installation shall comply with the other provisions of this section." ...i.e. Article 550, Section III.

Within Section III, note in particular 550.32(A). I interpret this as the disconnecting means adjacent to the mobile home is the SERVICE DISCONNECT. Now I ask you again, how many feeders can you run off the load side of the service disconnect into the "building"?

 

[websparky]

Gentlemen,

After re-reading 225.30, 225.33, 225.37, 550.10, 550.32 and 550.33, I agree that the multiple feeder is code compliant and would also say that a permenant plaque or directory is required.

 

[George Stolz]

Smart, I'm not seeing how you're concluding that the service disconnect that is apart from the mobile home is part of the mobile home. I'm not connecting the dots.

Dave, can you explain your conclusion? 225.30 seems to slam the door shut on this.

 

[websparky]

George,

These units are all designed and built this way. I can not see a better or safer way to address this common situation. I believe 225.30(B)(2) is valid because each individual unit is designed for 100A and when connected together they fall under "(2)". Is this a bit of a stretch? Yes. Is it less safe (as long as there are plaques)? I don't think so.

If not this way, what other way could this be resolved? These units are everywhere!

 

[George Stolz]

George,

These units are all designed and built this way. I can not see a better or safer way to address this common situation.

What about a simple 200A 1? disconnect on the exterior, near the marriage wall? One for each half. It would be fully compliant, and still be transportable in the future, with a quick removal of the riser.

I'm normally on the Minimalistic Express, but I wouldn't see a problem with an inspector failing this and requiring grouped disconnects outside the building.

Another perspective: Perhaps the only reason there is not a disconnect shipped on the outside from the factory is that they have no way of knowing where the trench is coming from. Know what I mean?

I believe 225.30(B)(2) is valid because each individual unit is designed for 100A and when connected together they fall under "(2)". Is this a bit of a stretch? Yes.

I agree on the stretchiness.

I just get to "sufficiently large" and hit a mental speedbump when it comes to being applied to a modular schoolroom.

Is it less safe (as long as there are plaques)? I don't think so.

That is a valid point, but it's a perilous road to walk. I don't think having more than six handles is much of a safety concern, but others bristle at the thought of more than six handles ever existing - when we start inflecting these things too strongly with our own prejudices, the ice can start getting a little thin to walk on, IMO.

"Right" is way easier to apply than "close enough." I get anxious about "close."

 

[iwire]

Why are you all calling a prefab class room a mobile home?

It is a manufactured building if I had my code book available I would point out the article.

 

[George Stolz]

Why are you all calling a prefab class room a mobile home?

It is a manufactured building if I had my code book available I would point out the article.

That would be Article 545, good call.

I see nothing in 545 that would alter the requirements of 225 in any way.

 

[websparky]

Nice try!

Nice try!

Bob and George,

Look at the first post again for what type of "structure" this is. It does not fall under 545.

 

[websparky]

George,

These have one service disconect within 30' of the units, no need for a 200A anything. The conductors running to the units are feeders.

 

[Smart $]

Smart, I'm not seeing how you're concluding that the service disconnect that is apart from the mobile home is part of the mobile home. I'm not connecting the dots.

...

I'm not concluding anything of the sort. Why are you even attempting to draw that conclusion?

My premise contends the service disconnecting means placed adjacent to the mobile home is at the load end of service conductors, no different than the starting question regarding the single exterior disconnect for a typical single property, single service situation. Are you of the impression that since exterior service disconnects are typically placed on the side of the buildings served that this has to be true in all situations? Is there a code item that requires an exterior service disconnect to be on the side of the building it serves?


Anyway, approaching this from yet another perspective, you guys have continually pounded 225.30 for justification of your position. If you really want to get technical on the not-a-service side of the issue, you should note the situation as initially described can be considered as all three "mobile home" structures are being supplied by one feeder. That's right... one feeder, three "additional" structures... the feeder being the conductors from the "regular" school building to the 600A pedestal. This feeder is then tapped at the pedestal.

240.21(B) Feeder Taps. Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through 240.21(B)(5).

Tap conductors. As used in this article, a tap conductor is defined as a conductor, other than a service conductor, that has overcurrent protection ahead of its point of supply that exceeds the value permitted for similar conductors that are protected as described elsewhere in 240.4.

Note it does not say a disconnect, OCPD, pedestal, etc. shall not be permitted at the tap, or that multiple taps cannot be made at the same point in the feeder. Follow up with 240.21(B)(5).

 

[Smart $]

...

Another perspective: Perhaps the only reason there is not a disconnect shipped on the outside from the factory is that they have no way of knowing where the trench is coming from. Know what I mean?

...

If you have a main disconnect on the outside it doesn't matter where the trench is coming from, this is where it would have to come to...

 

[George Stolz]

Smart, I don't have a flippin' clue what you are talking about. Let's establish some "givens."

• Meter pedestals have disconnecting means in them. The service stops there.
• The feeders enter these/this structure(s) for some distance, and then enter panelboards inside the structure(s).

225.32 requires the outside feeder disconnecting means to be treated just like a service. The specifications of "outside" given in 230.6 are even referenced.

Unless there is some section in Chapters 5-8 that says "Ignore 225.30, 225.32 when dealing with this" then they apply.

And I have absolutely no clue what the feeder taps business was about. Let's just pretend that didn't happen, because we still have not established a section that overrides the disconnecting requirements of 225, and until that happens, all other side-trips will be moot.

 

[iwire]

Bob and George,

Look at the first post again for what type of "structure" this is. It does not fall under 545.

Why you gotta say "Nice Try"?

It sounds like your trying to poke fun at us.

Thats OK cause I still think I am right about this.

I don't see anything in the opening post that says these where once designed to be used as a dwelling unit[b/] and now have been converted to class rooms.

Article 550 only applies to items that where designed to be used as a dwelling unit and either are still Mobile Homes or have been converted to other uses such as class rooms, job trailers, sleeping dormitories etc.

If these classrooms where designed from the ground up as class rooms they are not covered by 550 but are in fact covered by 545.

Carefully read the scope, definitions and 550.4(A).

I can dig out a picture or two of a job trailers listing and it is not listed as a Mobile home.

 

[George Stolz]

Bob and George,

Look at the first post again for what type of "structure" this is. It does not fall under 545.

Looking again, I agree with you, Dave.

This appears to be a "Mobile Home Not Intended as a Dwelling Unit" as described in 550.4(A), and 550.4(B) also seems to describe it.

But nothing in 550.33 modifies the requirements of 225.30 & .32 that I can see. So, we're left with those requirements with the addition of an insulated EGC as is additionally required in 550.33(A), IMO.

These have one service disconect within 30' of the units, no need for a 200A anything. The conductors running to the units are feeders.

I'm starting to see what you're getting at. 550.32 essentially implies (notice I did not say "states") that the service disconnecting means seperate from the structure is the disconnecting means required in 225.32.

I'm going to do some poking in the ROP's and see what I dig up. I am by no means an expert when it comes to mobile homes.

 

[George Stolz]

What the heck is this thing?

Manufactured Building. Any building that is of closed construction and is made or assembled in manufacturing facilities on or off the building site for installation, or for assembly and installation on the building site, other than manufactured homes, mobile homes, park trailers, or recreational vehicles.

Hmph.

We had a good discussion on this a while back, I'll go looking for it. I don't remember the outcome (if any).

 

[iwire]

Looking again, I agree with you, Dave.

This appears to be a "Mobile Home Not Intended as a Dwelling Unit" as described in 550.4(A), and 550.4(B) also seems to describe it.

George I am surprised.

You and I have talked about this before and agreed with me.

I am looking for that thread as I described my position fairly well there.

The bottom line is look at the manufactures tag for the listing.

It will say if it is a manufactured building or manufactured home.

Listings are funny like that..

That aside I am not sure where I stand on the OP.

As Dave says it's done all the time.

I have wired 5 section job trailers, (5 - 125 amp Feeders) 3 section cafeterias on job sites (3 - 125 amp feeders)

Not sure if it actually correct I try not think about it so hard, the inspectors are fine with it.

 

[websparky]

Why you gotta say "Nice Try"?

It sounds like your trying to poke fun at us.

Bob,

Don't you remember the old days? You and I go way back. We used to be able to bust each others chops! Lighten up!

 

[iwire]

Bob,

Don't you remember the old days? You and I go way back. We used to be able to bust each others chops! Lighten up!

I was laughing, I was not upset at all.

I tried to convey that with all the emoticons and the poor grammar (Why you gotta)

Bust away I got thick skin.

 

[George Stolz]

George I am surprised.

You and I have talked about this before and agreed with me.

I think this is the thread. I'm about to re-read it to get to the conclusions.

The bottom line is look at the manufactures tag for the listing.

Good point.

Not sure if it actually correct I try not think about it so hard, the inspectors are fine with it.

Good idea. I'm giving up on this for a while, everybody's making too much sense.