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#5163 - 11/07/01 08:16 PM New Service or Sub feed?  
Bill Addiss  Offline
Joined: Oct 2000
Posts: 3,878
Question from 'Kimberly'
No one seems to have a definite answer for the following: We are building a secondary dwelling (owner occupied) behind the main house. Are we required to have seperate service, or can we subpanel from the main house panel? The main house has a 200 A panel. We have spoke to 3 inspectors, who say it is up to our electrician. Our electrician says he needs to know from the building department. PG&E wasn't very helpful either. Confused!???????

I've asked for more details. I think this is an interesting topic to discuss here.


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#5164 - 11/07/01 08:33 PM Re: New Service or Sub feed?  
Fred  Offline
Joined: Apr 2001
Posts: 449
Straughn, IN 47387
It depends on the total calculated load of both dwellings. Your electrician should be able to figure this for you. For example: If the existing dwelling is 2000 sq.ft. and total electric I would guess a sub feed to another dwelling of any size would not be a good idea. You simply need to calculate the total load of both dwellings to determine if 200A service is adequate. The only reason I can think of that would definitely prohibit a second service is if the dwellings were to be connected and not have proper fire separation.

#5165 - 11/07/01 11:15 PM Re: New Service or Sub feed?  
electure  Offline

Joined: Dec 2000
Posts: 4,261
Fullerton, CA USA
Down here (SoCA), you have to give the other dwelling a seperate address to have SCE provide another meter.
(I'm also interested in the details)

#5166 - 11/07/01 11:28 PM Re: New Service or Sub feed?  
Joe Tedesco  Offline
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
See the 1999 NEC, Section 230-40, Exception No. 3.

Joe Tedesco, NEC Consultant

#5167 - 11/07/01 11:31 PM Re: New Service or Sub feed?  
Bill Addiss  Offline
Joined: Oct 2000
Posts: 3,878
I think that, load aside, the decision to go with a new service or sub-feed brings up some interesting questions when there may be common utilities being used or coming from the first house. ie; a water pipe.


#5168 - 11/07/01 11:37 PM Re: New Service or Sub feed?  
Bill Addiss  Offline
Joined: Oct 2000
Posts: 3,878

Didn't see your post.
If that method was used, what would you do about a water line that runs from the first house to the second structure? How would bonding work so as not to create parallel paths?


#5169 - 11/08/01 08:19 AM Re: New Service or Sub feed?  
Redsy  Offline
Joined: Mar 2001
Posts: 2,056
Bucks County PA
There may be no definitive answer, only practical opinions. I, also wonder about the second address. Is this property sub-divided? Will it be possible to sell this home in the future? Or rent it out to someone? From a practical standpoint, I like the separate service, as long as the PoCo permits it.

#5170 - 11/08/01 12:04 PM Re: New Service or Sub feed?  
resqcapt19  Offline
Joined: Nov 2000
Posts: 2,148
How is 2 services on one property with a common water line any different than 2 buildings next door to each other on a common water line?


#5171 - 11/08/01 01:02 PM Re: New Service or Sub feed?  
ElectricAL  Offline
Joined: Oct 2001
Posts: 597
Minneapolis, MN USA
To bond or not to bond. That is the Question. [Linked Image]

That pesky service disconnect neutral - GEC bond! I REALLY like some of the UK designs.

To Kimberly,

Sounds like the power company and local inspection in your area will allow the second meter but don't require it. IF your existing 200 Amp service load calculation with the new dwelling added to it is workable (your electrician does this calculation, ask for a copy and talk through it with him/her), then the choice boils down to how much the different installations cost, and how much you want to buy. The electrician may not want to take the time to do this, if so, talk to another.


Al Hildenbrand

#5172 - 11/08/01 02:24 PM Re: New Service or Sub feed?  
Bill Addiss  Offline
Joined: Oct 2000
Posts: 3,878

Normally houses (or structures) next to one another would be out on a 'branch' of the water main, wouldn't they? I was thinking about the service being bonded to the waterline out at the 2nd structure and it then running back through the first House. The waterline at the 1st house is bonded to service neutral also. Wouldn't there be current flow on the waterpipe all the time? One thing I'm thinking of is someone doing any plumbing work could be in danger, especially if one of the service neutrals went bad and no one knew about it.

Also, wouldn't/couldn't there be some difference in potential from this waterline to other conductive objects in contact with earth?


[This message has been edited by Bill Addiss (edited 11-08-2001).]

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