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service upgrade #39900 07/06/04 07:30 AM
Joined: Jul 2004
Posts: 3
bukuboy Offline OP
Junior Member
HO wants 150 amp service upgrade to 320 amp continuous, 400 amp peak. This is underground feed and 60 feet from ground transformer to meter base. Present interior loadcenter is back-to-back from meter base. thinking about runnin' parallel 3/0 cu in 3" pvc and double lug both line and load side of 320/400 amp meter base. Will place one 200 amp interior loadcenter where the 150 amp one now resides(will discard present 150 amp loadcenter) and place 2nd 200 amp interior loadcenter in attached garage which is 3 feet from 1st loadcenter. The two 200 amp loadcenters will be connected with 2" steel conduit. Is it code compliant(Tampa bay,Fl.), to run the feeder wires of the 2nd loadcenter through the 1st loadcenter, through the 2" steel conduit and on to the 2nd loadcenter? In essence, the 1st loadcenter acts as a raceway for the feeders of the 2nd loadcenter. Can I just use the main breakers in the loadcenters as the disconnects rather than having ext. disconnects? Again, the loadcenters are 3 feet apart although separated by an 8" wall.
Thanks ---- Billy

[This message has been edited by bukuboy (edited 07-06-2004).]

[This message has been edited by bukuboy (edited 07-06-2004).]

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Re: service upgrade #39901 07/06/04 02:45 PM
Joined: Nov 2003
Posts: 269
electricman2 Offline
I believe 230.7 will require separate raceways to each load center. Ran into this situation with a service for a golf cart storage bldg. with two 200A loadcenters.

Re: service upgrade #39902 07/06/04 02:52 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline

I don't think you'll find many inspectors that would feel that the disconnects are grouped as required since they are in different rooms. That being the case, you'll need your service disconnecting means outside.

Look at 312.8 to determine if you have enough room for the pass through feeders.

Then, run this by your local AHJ, there may be some local restrictions.


Few things are harder to put up with than the annoyance of a good example.
Re: service upgrade #39903 07/06/04 03:07 PM
Joined: Jul 2004
Posts: 3
bukuboy Offline OP
Junior Member
electricman2, I believe that 230.7 states that branch and feeder conductors can't be in the same raceway as the service conductors. In my case, the feeder and branch conductors are in the same raceway(the 1st loadcenter) but the service conductors aren't. Thanks ---Billy

Re: service upgrade #39904 07/06/04 04:57 PM
Joined: Dec 2003
Posts: 751
earlydean Offline
Remember as well, that the six conductors in the 3 inch PVC need to be derated to 80% of ampacity because you have installed more than 3 current carrying conductors in a single raceway; 310.15(B)(2)(a).

Might be better to run separate cables or conduits, one to each panel.

Re: service upgrade #39905 07/06/04 08:08 PM
Joined: Nov 2003
Posts: 269
electricman2 Offline
If I am interpreting the info in your post correctly, the conductors passing through panel 1 to panel 2 are service conductors and would not be allowed. As Tom said you could put a disco outside. Then they would be considered feeder conductors.

Re: service upgrade #39906 07/06/04 09:25 PM
Joined: May 2003
Posts: 2,876
e57 Offline
The last few 320A/400 Services I've done have been 2 - 200A cb's as feeder distribution, as "all in one meter main". Conductors sound right, but confirm it... Assuming this is a single occupancy residence... Check 310.15.6B if allowed in your area. Some areas with lots of AC don't allow this under sizing.

Our Power Company doesn't like up-grades of this much without checking the engineering for the neighborhood first. Most of thier transformers went in in the 60's, and are under-sized by todays standards.

230.7 I don't believe will be an issue as they are both feeders, if you used a meter/main! If not, you would have unprotected service conductors though a panel, not cool!

Still either way, I would pull the conductors to a can, then the panels. Or go direct.

But the meter/main combo is the way to go! No grounding/bonding nightmares, and once you and a friend lift it into place, it's done. (The last one was 4'X 5'tall, and wieghed more than I did....)

Mark Heller
"Well - I oughta....." -Jackie Gleason
Re: service upgrade #39907 07/09/04 05:13 PM
Joined: Jul 2004
Posts: 3
bukuboy Offline OP
Junior Member
What I've decided to do is get a meter main combo with 2 200 amp discos outside and feed two 200 amp interior loadcenters as subpanels with separation of neutrals and grounds. Sounds like the easiest but probably more expensive. Thanks guys ---Billy


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