400A Service - Remote Meter Location

[radiopet]

Hey Guys,

I had an AHJ and Guy call me today asking for references for a situation he had so i figured I would run it by you all....found it interesting.

1.) The dwelling has a 400A service ( (2) 200A Panels side by side within the dwelling )

2.) The meter can is being installed on a large board setup about 75' away from the house....so the service latteral will hit a gutter on one side of the board and feed back through to a 400A meter can and a 200A meter can for future garage I think.

3.) The told me that the guy is running (2) 2 inch PVC Sch 80 from the meter to the panels located inside the dwelling....again 75' away...but once inside the house will only go about 3 feet so it is at the point of entrance of the actual dwelling where the panels are located.

Now.......here was the question.....and while I felt it was clear I now question it so i ask you guys as well...

A.) he allowed the guy to use 310.15(b)(6) to size each (set) of 3 conductors to each 200A panel in its own 2" PVC conduit.

However it would appear 310.16 is the determineing table here....

Anyway he allowed (2) 2" conduits to hold (3) 2/0Cu Conductors and one conduit went to each 200A panel inside the dwelling.

To me 310.15.b.5 MAY apply to only (1) set of service enterance conductors.....yet we see all the time a 400A meter can with (2) 200A panels on the other side of the wall and fed from (2) different 4/0 AL SE cable...

While again we see this all the time......does this not confuse the application of 310.15(b)(6)

Any thoughts guys.....

 

[suemarkp]

Where do you see a limitation in 310.15(B)(6) to a single set of service entrance conductors? It just says service entrance conductors, service lateral conductors, and main power feeders. Nothing about parallel conductors or multiple sets of conductors.

Do you really see any practical difference between two 2/0 feeds to a house, each terminating in a 200A panel, and a house with only one 200A panel fed by 2/0 copper? How is one any less safe than the other?

 

[iwire]

Where do you see a limitation in 310.15(B)(6) to a single set of service entrance conductors?

Mark I find this section of code tough to figure.

That section limits the use of the table to the "Main power feeder(s)" to a building.

If you divide the main power feeder in two now IMO neither is a main power feeder.

Does this make a difference? It might.

As I understand that table it works due to load diversity for an entire home.

In an extreme example someone might fill one panel entirely with all heavy loads (lets say electric heated home) and in the other panel have only a few circuits.

Under those conditions I can see the possibility of overloading one of the feeders.

But keep in mind as far as I am concerned that table should go and we should all just use 310.16.

 

[don_resqcapt19]

Bob,

If you divide the main power feeder in two now IMO neither is a main power feeder.

The code defintiton of "main power feeder" does not require that it supply the main portion, or any other portion for that matter, of the power to the dwelling unit. Also in this case, we don't have any feeders, just service conductors.
Don

 

[radiopet]

The reason I ask is because the NEC Handbook states as it has to be (1) set of 3 wire's...and makes a point in saying that.

I asked Mike about it and he felt the 310.15(b)(6) would not apply to all feeders since their are more than 3 wires to this service technically.

I was trying to give advice on it...and the way I actually read it.....both lines would be part of the service and each panel would only have 3 wire supplies to it.....

As for the protection from overloading...each panel will still have a 200 Main Breaker in each panel so that portion is not a large concern.

he point is.....in reading 310.15.b.6.... is their a limit to the type of install that many have always been doing....whe installing a 400 A service...that has two sets of conductors, one for each 200A panel if tha is the install method.

 

[radiopet]

Where do you see a limitation in 310.15(B)(6) to a single set of service entrance conductors? It just says service entrance conductors, service lateral conductors, and main power feeders. Nothing about parallel conductors or multiple sets of conductors.

Do you really see any practical difference between two 2/0 feeds to a house, each terminating in a 200A panel, and a house with only one 200A panel fed by 2/0 copper? How is one any less safe than the other?

Suemarkp,

I am refering to the installation requirement not safety concern...while that is part of it.....when you read the NEC Handbook in regards to this hot topic is starts off by saying...in no less terms....that it applies to only (1) set of 3 wire conductors....

While in my opinion since you have (2) different 200A panels each fed with its own 3 wire setup.......and without reading the explantion in the handbook...it seems like 2/0CU or 4/0 AL would be allowed.....but then the explanation comes in....

I asked mike about it and he felt that 310.15(b)(6) would not apply here as it was more than (1) set......so his reply meets what the handbook is saying...but I have gotten many different responese on this..

I am sure you have seen plenty of 400A services where they have a 400A meter can and it feeds (2) different 200A panels directly behind it...each are fed with a 4/0AL SE....and no one has ever had a problem with it......

So the question is...how is the installation i posted any different and if it is...how.....does this not make the installation above also wrong..

 

[radiopet]

I think I understand here.....but still not sure...lol.....

Mike says that 310.15(b)(6) cant apply to this becasue of the (2) sets of conductors...

Also says that the installs that have been done for years around the country where you have a 400A meter can and it has (2) 4/0AL coming out the back each feeding a different 200A panel is a violation as well...as it would not meet the allowance of 310.15(b)(6)..

Man I can bet their are THOUSANDS of services for 400A being installed all the time........but are they violations?

 

[suemarkp]

Handbook commentary is not code, but the guys that write the commentary should have some clue as to what was intended. If you read just the code, I don't know how anyone could fail this because the code makes no mention of limiting 310.15(B)(6) to one set of service conductors. Code language should be enforced, not intent that was not actually specified. They should write what they mean, and not leave implicit intentions. The skilled electrician should be the safeguard from doing something unsafe or stupid that the code language happens to allow (because it was poorly written).

 

[iwire]

Bob,

The code defintiton of "main power feeder" does not require that it supply the main portion, or any other portion for that matter,

I disagree, I don't see how anything that is a "main' feeder can be divided and still be the main.

I

 

[don_resqcapt19]

Bob,

I disagree, I don't see how anything that is a "main' feeder can be divided and still be the main.

Remember we are talking about the code here and not the real world meaning of the words.

For application of this section, the main power feeder shall be the feeder(s) between the main disconnect and the lighting and appliance branch-circuit panelboards(s).

The code does not say that a "main power feeder" has to carry the main part of the load. If the would have just left the defintion out of the section then "main" would have meant main as the word is normally used in the real world.
Don

 

[radiopet]

lol....so while I read this debate i remember I love bringing things up like this to help people think.....lol.....Don are you saying 310.15(b)(6) would allow the use of 2/0CU or 4/0AL to feed each panel in the example listed above.

 

[radiopet]

I disagree, I don't see how anything that is a "main' feeder can be divided and still be the main.

I

Bob, Is it no different than a single set of mains....just using (2) 200A panels as such......each set is sized on 310.15(b)(6).......see it all the time with back to back 400A cans and (2) 200A panels.....using 4/0AL....

Are we saying this entire setup is wrong.......OR...are we saying that chances are the meter can is not REALLY a 400A cont. can so it is probably a 320A rated meter....so using 4/0AL...which on table 310.16 is good for 180 A...so combined we have 360A....however the main OCPD within each panel is rated at 200A......ARE the conductors protected.... since the 240.6 lists 175A breaker and then jumps to 200A...

Ie: Section 240-3(b) permits "the next size up device" if the conductors are not part of a multioutlet branch circuit supplying receptacles, and the ampacity of the conductors does not correspond with the standard ampere rating of a overcurrent protection fuse or a circuit breaker as listed in Section 240-6(a), and the next higher standard rating selected does not exceed 800 amperes.

Are you thinking THIS is why 4/0AL is seen alot......

 

[suemarkp]

The power feeder question isn't relevant to the original question, because these are service conductors and not feeders. I would say this is not wrong. But the only opinion that matters is if your inspector says its wrong.

The full application details of section 310.15(B)(6) is never going to be resolved until they rewrite it yet again.

4/0 Al may work regardless, if the calculated panel loads are 180A or less on each panel. But I think the gist of your question is whether 310.15(B)(6) or 310.16 should apply to a split service. I used two sets of 3/0 copper on my 400A service because I wanted to avoid this issue with the inspector.

 

[radiopet]

Suemarkp,

Thats the point really.....and I tend to agree but since most of the AHJ's around here actually call me anyway....figured I would NAIL this on to the tombstone so to speak.

Mike Holt says it simply does not apply.....If I believe anyone it would most certainly be him......but again i can't see where it defines only (1) set of service conductors......as it talks about that WAY before it jumps into the feeder issues.

Personally..........I think the meter can the guy is speaking of is 320A rated.....the local POCO happens to use 320A Meters for 400A as well...even Cont. Rated....they just perfer to order only one meter base layout I guess.

From what I gather...the calculated load ( optional method I think )the guy said was combined at around 300A.....but again from what I gather the custom built home was calculated before knowing exactly what was in it.....so they calculated and ballooned it........

Anyway.......with deversified loads and so on....I have seen 12,000 sq ft homes on a 400A service and a few on a 200A service.....really depends I guess.

I am with you however......hard to argue with the AHJ...as I spoke with one who said...well we allow 4/0 SEC to seperate 200A panels (2) of them...from a 400A meter can all the time........he said quote "we have no plans on stopping now..."

 

[don_resqcapt19]

radiopet,

Don are you saying 310.15(b)(6) would allow the use of 2/0CU or 4/0AL to feed each panel in the example listed above.

Yes. In this case we don't even have to think about the "main power feeder" issue as the conductors in question are not feeders. They are service conductors and the sections say that you can use the reduced conductor size for service conductors.
Don

 

[radiopet]

Don,

So I have to ask......why does Mike see it differently...as I also agree in that i also do not see where it defines (1) set of conductors....versus (2) sets...

It's that first line of defining examples that says Service Enterance Conductors......way before it gets to the feeder reference....

Thats why I bought it up......some GOOD instructors and AHJ's all disagree on this...I guess making it VERY hard to reject on an inspection.

I think in the example however the guy is going to be fine either way based on the demand load.......the calculated demand is less than 300A total anyway...using the optional method I am told.

 

[don_resqcapt19]

Radio,

So I have to ask......why does Mike see it differently..

I have no idea why Mike reads it differently...I see nothing that limits the application to a single set of service conductors.
Don

 

[George Stolz]

At first, I was thinking Don was being clever in some way.

I just read the section for the umpteenth time and have come to the conclusion that Don is right. So long as the fifteen () sets of service conductors supply an individual dwelling unit, we can use Table 310.15(B)(6) until we're blue in the face.

I'd never considered this scenario - a big house, dealing with the service conductors instead of feeders. I'd always thought about multifamily in terms of this section.

Good topic, Radio!

 

[George Stolz]

I asked Mike about it and he felt the 310.15(b)(6) would not apply to all feeders since their are more than 3 wires to this service technically.

I think the text "3-wire" in this section is referring to a system, as opposed to an actual conductor count.

The NEC is replete with "single-phase, 3-wire" and "three-phase, four wire" references.

Voltage (of a circuit). The greatest root-mean-square (rms) (effective) difference of potential between any two conductors of the circuit concerned.
FPN: Some systems, such as 3-phase 4-wire, single-phase 3-wire, and 3-wire direct current, may have various circuits of various voltages.

As an aside, my proposal to add an FPN to the voltage definition was rejected:

Add FPN to definition:
FPN No. 2: And stuff.

Substantiation: The current FPN is good, but more generalization is needed.

 

[radiopet]

Radio,

I have no idea why Mike reads it differently...I see nothing that limits the application to a single set of service conductors.
Don

So you see two sets of lets say (3) 4/0AL conductors with (3) in each raceway to each 200A panel as being a single SET of Service Entrance Conductors in the application of 310.15(b)(6)