I can’t seem to find the answer in my code book, and Cauldwell’s book just mentions this situation, in passing:
On the outside of the house, a couple of feet from the meter is a box with the main disconnect. Inside the house, about 2 feet from the outside box, is the box with all the house circuit breakers. 100A service.
My question concerns the ground bus for the inside box. Should it be isolated from the inside neutral bus? Or can the inside ground bus be tied to the neutral IN the inside box? Cauldwell seems to be implying that because the two boxes are so close together the inside box can be considered a ‘main’ box?
No local codes to guide me.
Thanks.
Replies
If they're so close together, why is there a disconnect.
I'm thinkin' that cause its the second stop, the "main" is indeed a subpanel.
Having said that, i'm sure BillHartmann will be coming by shortly to educate us both.
Power company requires a disconnect outside.Thanks.
You nailed it exactly, "main disconnect!" The point in the whole house where the neutral and ground should be tied, and bonded together, is at the "main disconnect." In fact, the main disconnect is the one and only place where the two are allowed to be bonded together.
Where are you? In Michigan they only require an outdoor disconnect if the service cable doesnt enter the main panel as soon as the cable enters the house.
Got it. Thanks to all.
I would pop the cover on the outside disconnect and see how it is wired. Don't assume that it is wired a certain way just because it is supposed to be!
I have uncovered everything imaginable checking out electrical equipment.
Service entrance appear to be one of areas that most deviate from the specific wording the NEC. Sometime more, sometimes less, sometimes just different.
It maybe from specific local amendments, local practices, local interpretations, and/or POCO requirments.
Without going through and reading the specific words and coma (and probably get them confused) the service entrance is the AREA where the neutral and ground electrode conductors are bonded.
For a "classical" installation with a mast, meter on the outside and a line run into the house to the main pannel the AREA where this can happen is anyplace from the where the neutral enters the mast through the meter box into the main panel. The NEC handbook has a drawing showing that.
"250.24 Grounding Service-Supplied Alternating-Current Systems
(A) System Grounding Connections A premises wiring system supplied by a grounded
ac service shall have a grounding electrode conductor connected to the grounded service
conductor, at each service, in accordance with 250.24(A)(1) through (A)(5).
(1) General The connection shall be made at any accessible point from the load end of
the service drop or service lateral to and including the terminal or bus to which the
grounded service conductor is connected at the service disconnecting means."
Now when you run a feeder to another structure you are allow to run 3 wires and rebond the neutral and ground electrode at the panel in the other structure if there are no other metallic paths between the structures.
I don't have a copy of the 2008, but I understand that option has been removed.
However, you are talking about something a little different.
One of the concepts with grounding and bonding is that any grounded or metal objects in a structure (or immedate area) are guarantee to be at the same potential.
It sounds like this is all mounted on the house, just part inside and outside. That is all one structure so the bonding would be at the meter/disconnect and 4 wires run to the inside sub-panel with isolated busses.
the sub-panel may or may not have a main breaker.
Now, if the POCO landed a pole at the lot line and wanted the meter and disconnect there and you than ran the feeder 100 ft to the house it would be a much different answer.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Forgot the perty picture..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.