Hypothetical-Table 310.15(B)(6)

[infinity]

I have a single phase residential service install with 200 amp meter enclosure fed with #2/0 per T310.15(B)(6). The first panel has dual lugs on the main and feeds an adjacent second panel. Each panel is rated at 200 amps and has a 200 amp main. Calculated load is less than 200 amps. Are the #2/0's compliant?

 

[acrwc10]

Are the "Dual lugs" before or after the OCP?

 

[infinity]

Are the "Dual lugs" before or after the OCP?

Before, on the main of the first panel.

 

[acrwc10]

As I see it, if you have a 3 wire feed you are fine. Once it goes into the panel gets fused and bonded then you need to run larger conductors to the next panel.

 

[Dennis Alwon]

Interesting poser!!! Let me present it this way -- if it were dual lugs in the meter would you allow this with 2/0? My response to that would be no, but you are using only one 2/0 to the meter and although it is the same result I think your way is compliant. Is it any different than if you used a feed thru panel? Same results...

 

[chris kennedy]

Are you questioning the fact it doesn't say "panelboards"?

For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit.

 

[Dennis Alwon]

As I see it, if you have a 3 wire feed you are fine. Once it goes into the panel gets fused and bonded then you need to run larger conductors to the next panel.

Why not. I can use a fed thru panel.

 

[augie47]

It scares me so much, I'd grasp at straws and say "Not Code" based on the singular word "panleboard" in 310.15(B)(6)

 

[Smart $]

It scares me so much, I'd grasp at straws and say "Not Code" based on the singular word "panleboard" in 310.15(B)(6)

But...

...the sentence with panelboard applies only to the main feeder, not SE/SL conductors.

... For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard...

 

[wireguru]

id say no because the 2/0 between the first panel and second is not carrying the entire load of the dwelling.

 

[Dennis Alwon]

id say no because the 2/0 between the first panel and second is not carrying the entire load of the dwelling.

The first one is.

 

[Smart $]

The first one is.

The conductor between the first and second panel is still a service entrance conductor. Even considering it a tap, its ampacity as determined by other parts of 310.15 must only be not less than the calculated load on the second panel.

 

[Dennis Alwon]

The conductor between the first and second panel is still a service entrance conductor. Even considering it a tap, its ampacity as determined by other parts of 310.15 must only be not less than the calculated load on the second panel.

I know that so what is your point. I said the first wire is carrying the entire load. The second does not but it does not need to be large then the service conductors so why not.

If I used a 200 amp feed thru panel fed from the service I certainly can run the same size conductor to the second from the feed thru lugs.

 

[Smart $]

... Are the #2/0's compliant?

Yes (IMO)...

...but what I don't like is the possibility of a 400A load could be placed on the 2/0's without the main breakers tripping... yet I can find no violation. There ought to be a maximum combined disconnecting means rating for service conductors, similar to max' fuse, max' circuit breaker for motorized equipment.

 

[jetlag]

It scares me so much, I'd grasp at straws and say "Not Code" based on the singular word "panleboard" in 310.15(B)(6)

I agree 100 % , please tell me I am misunderstanding something , 2 200 amp mains can put a 400 amp load on the 2/0 . Dennis mentioned a fed through is allowed , I thought a fed thru at the bottom of a buss has already passed through the panel main . That is not what he has , He is lugged in before the main . The calculated load doesnt matter, people can add any thing they want to the panels . I say the second panel has to pass thru the main on the first unless there is a 200 amp outside disco .

 

[Smart $]

I know that so what is your point. I said the first wire is carrying the entire load. The second does not but it does not need to be large then the service conductors so why not.

If I used a 200 amp feed thru panel fed from the service I certainly can run the same size conductor to the second from the feed thru lugs.

You said first one is carrying entire load. I'm just saying that even though the second doesn't fall under 310.15(B)(6)... it is likely sized large enough for the calculated load of panel 2.

 

[hurk27]

I agree 100 % , please tell me I am misunderstanding something , 2 200 amp mains can put a 400 amp load on the 2/0 . Dennis mentioned a fed through is allowed , I thought a fed thru at the bottom of a buss has already passed through the panel main . That is not what he has , He is lugged in before the main . The calculated load doesnt matter, people can add any thing they want to the panels . I say the second panel has to pass thru the main on the first unless there is a 200 amp outside disco .

230.90(A) exception 3 seems to allow just this installation, I don't like it, and would never do an install like this, but it does seem to be allowed?

 

[cadpoint]

This link was given today for another OP!
http://www.milbankmfg.com/products/Catalogs/CatalogFiles/PDF/5168.pdf

While almost similiar to the running OP statement, let me defer...

Now note that the 100 has pass through Lugs but both @ the top also has both are shown "Tapped" on the Line Side of the service!

Does that Help ?

 

[jetlag]

230.90(A) exception 3 seems to allow just this installation, I don't like it, and would never do an install like this, but it does seem to be allowed?

wow , this is hard to swallow , can someone tell me how this is different from installing a 400 amp panel on 2/0 conductors ? We can have up to 6 disconnects but dont you have to add the loads ? What if I install 6 - 200 amp panels on a 2/0 and just say ,well ,the calculated load RIGHT NOW is less than 200 amp

 

[hurk27]

This link was given today for another OP!
http://www.milbankmfg.com/products/Catalogs/CatalogFiles/PDF/5168.pdf

While almost similar to the running OP statement, let me defer...

Now note that the 100 has pass through Lugs but both @ the top also has both are shown "Tapped" on the Line Side of the service!

Does that Help ?

The difference is the tap is at the meter, and the only possible over load would be at or ahead of the meter, in the OP the tap is at a panel located in the dwelling and the conductors that could be overloaded are "inside" where they could cause a fire, I have done many SEC taps outside where the calculated load was not over the rating of the SEC conductors but adding of the breaker handles was, but never after the conductors reached an inside panel.