COMMUNITY FORUM

junker

01:27PM | 06/25/07
Member Since: 06/24/07
2 lifetime posts
Bvelectrical
I'm having an argument with the electrician about the wiring of a sub panel for a house that I have been asked to watch built for a friend that is unable to be present.

The way I understand it is that the MCO (MainCutoff) panel is the one that has the main service breaker and the meter no matter where it's located and it's here that the ground and neutral are bonded. And in this case it's on a pole by the road.

1.Any subsequent panel is considered a sub panel and requires a floating neutral (ground and neutral busses seperated)

2.AND if the panel has more than 6 breakers it requires a main cut off breaker. To me this sounds like a no brainier and for safety reasons reasonable.

The problem is that the electrician won’t make the modifications unless I can show in the electrical code where this information is located. I have a 1996 NEC book but am having trouble finding the sections I want and was hoping that someone could help me out with these two items

Thanks

Tom O

03:42PM | 06/25/07
Member Since: 09/17/02
477 lifetime posts
1. Not always. In this case, the feeder to the house from the pole can be a 3 wire feeder consisting of 2 hots & the neutral (check with local code enforcement officials for local requirements). if that is the case, then the neutral is bonded to the enclosure and two more ground rods must be installed at the house (unless a single rod can be tested to 25 ohms or less which is unlikely). However, if a 4 wire feeder is installed (2 hots, one neutral and one equipment ground) then the neutral and equipment ground do not conn3ct together at the house panel. 2 ground rods are still needed, but this time they would connect to the equipment ground.

Also, any bonding that is required for a service entrance for a house would also be required for a house that is fed by a feeder. This means connections to metal water lines, etc.

2. This time you're right. In the 2005 National Electrical Code, see 225.32 and 225.33 Article 225 is frequently overlooked by many electricians.

Billhart

06:15PM | 06/25/07
Member Since: 04/25/05
1916 lifetime posts
The house is a separate structure from the pole. This you can use a 3 wire connection from the pole to the panel in the house.

And house needs a disconnect, plain and simple (or upto 6 grouped together). But it does not have to have overload protection as that is provided at the pole.

Now services are an area that the POCO and the AHJ often have local rules that either limit what portions of the NEC that can be used or in some cases even differ from the NEC.

So if this is an area with premitts and inspection I would talk to the inspector about your concerns.

Also I want to disagree with Tom slightly.

There are a number of ground electrodes that can be used and ground rods or only one type.

Code requires that if you have a an income metalic waterlines that is at least 10 ft long, underground then it MUST BE USED as a ground electrode. However, the code realize that water lines are oftne replaced with plastic and thus it can't be the sole ground electrode.

And IF you have a UFER Ground Electrode (concrete encased rebar or copper wire in the footing) then it must be used. The wording is confusing, but the intent is that new constrcution have a ufer ground, but they realize that it is not practical to add it if it was not installed with the footing when poured.

And some locals are not enforcing the require to install the ufer.

And there are other allowed ground electrodes and some that are required to be used, if available. But they are not common in residential construction.

Thus if you don't have the ufer and require another ground electrode then ground rod(s) are used and it takes speicalized test equipment so that are not usually tested and thus 2 are automatically installed.

junker

10:39AM | 06/26/07
Member Since: 06/24/07
2 lifetime posts
Thanks for the replys and will be checking on the items you brought up.

Now on a different note

After I posted this question one was asked of me and while it is in the same vein was wondering if there is a different answer

This is concerning a Condo building where the main panel and service is located in an electrical room that is only accessable by personal with keys.

Question is does the panel in the indivual unit require a seperate disconect breaker??? More than six breakers

Thanks

Billhart

12:52PM | 06/26/07
Member Since: 04/25/05
1916 lifetime posts
The purpose of the 6 operation (pulls of breakers)or less is to allow old Split Bus panels. Those had no main breaker, but breakers for each 240 load and one breaker that feed a sub-bus for 120 volt loads. I don't think that any of those are avaialable anymore.

And the rule is only used for special circumstances. One common reason is if you have home with a 320/400 service. Panel larger than 200 amps are commercial and expensive.

The 6 breaker rule allows you to have 2 150-200 amp panels with main disconnects to be mounted side by side.

Back to your question. Yes, a condo or appartment occupant is suppose to be able to cut off all power to their unit.

Tom O

12:19PM | 06/27/07
Member Since: 09/17/02
477 lifetime posts
The general rule is that each occupant shall have ready access to all overcurrent devices supplying their occupancy. As usual, there is an exception for multiple occupancy buildings. If building management provides maintenance and there is continuous building management supervision, then it is peremissible to limit access to the service equipment and feeder breakers.

Bill is correct about the various grounding electrodes. I'm so used to answering a similar question about feeds to outbuildings that I didn't fully engage my brain.

Tom
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