Single family residential service.

[nizak]

I am looking to install a 200A 8 space single phase 3R panel with feed through lugs located on the exterior of the dwelling, fed from the POCO meter base. I plan to run(3) 2/0 CU conductors from the meter to feed this panel.At this location I have established my first point of disconnect. From this panel I plan to go from the lugs located at the bottom of the bus to an interior 200A panel directly behind it. I also plan on feeding a 125A panel in another portion of the house with a 2 pole breaker from the 3R panel, that will be used for various loads and for future expansion when an addition will be added next year.

Here is where I need some clarification. I will be supplying "all loads that are part or associated with the dwelling" from a combination of the 2 interior panels. Can both of these panels be wired with conductor sizes found in 310.15(B)(6) or do they need to sized to 310.16(75degree)? I assume that both become 4 wire installs once they leave the first point of disconnect. Thanks a lot.

 

[jumper]

Since neither interior panel individually carries the full load, but rather the load is split, I would say you gotta use 310.16 for both interior panels.

 

[nizak]

Am I correct in saying that for the 200A interior panel the wire size would not have to be larger than the 2/0 feeding the main service disconnect?

 

[texie]

Am I correct in saying that for the 200A interior panel the wire size would not have to be larger than the 2/0 feeding the main service disconnect?

This is where the rub is in 310.15(B)(7). It is contradictory. And the complete rewrite of this in the 2014 edition is just as unclear.

 

[jumper]

This is where the rub is in 310.15(B)(7). It is contradictory. And the complete rewrite of this in the 2014 edition is just as unclear.

MH and others submit proposals and keep getting rejected. It really is a PITA.

 

[suemarkp]

I would hope you could still run 2/0 to the interior 200A panel, as that is what is feeding the feed through panel which feeds the entire dwelling. If 2/0 is OK for that, how can it not be large enough when some of the circuits are removed? I agree the words are not clear, but I hope they still recognize logic. 310.15(B)(7) kind of says this, but it uses the old language of "feeder for an individual dwelling unit". It does not say entire dwelling unit.

For the 125A panel, I think you need to use the regular table for that one.

 

[James L]

When in doubt, I would suggest calling your city planning department to see how they will interpret/enforce. Every municipality is different.

On a whole-house remodel a few years ago, I installed the same 200a, 8 space, 3R panel and fed through to a 225a MLO - ran 4/0 AL from meter to 3R and 4/0 from 3R to MLO. There wasn't any issue with the conductor sizing

I used this configuration so that two air conditioners right next to the 3R could be fed from outside (with no a/c disconnects) instead of from the MLO all the way across the house

 

[mwm1752]

Is this a lateral/riser you only mentioned meter to panel

 

[arion]

for 200A if the feeders are in conduit that should be 2x3/0 1x2/0 1x1/0
for the poco feeder in to the meeter base if in conduit it should be 2x4/0 1x3/0

 

[don_resqcapt19]

Am I correct in saying that for the 200A interior panel the wire size would not have to be larger than the 2/0 feeding the main service disconnect?

Yes. A dwelling unit feeder never has to be larger than the service conductors.

310.15(B)(7)(3) In no case shall a feeder for an individual dwelling unit be required to have an ampacity greater than that specified in 310.15(B)(7)(1) or (2).