Thread: Large Residential Service

Recently inspected a 10k foot home. The main disconnect was located outside and had 3 100Amp double pole breakers with a single pole unlabeled breaker below it, and 1 200Amp breaker with a nsingle pole unlabeled breaker beneath it. The panel itself was rated for 600 Amps. If I count the amps do I have 500 amp service? Anyone know whats going on here? Thanks.

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First, what are all those breakers up at top, and that open breaker twist-out?

I am *hoping* they are protected by one of those mains, if not, there is a problem (but they probably are).

To answer your question, though, no, you cannot simply add up the separate main disconnects (maximum of 6) to determine the service size, and the rating on the equipment is simply the maximum rating use allowed.

I have always simply stated it as: 'There are three 100 amp main disconnects, grouped together within the service equipment.'

That does not mean the building has a 300 amp service, and it is likely that the combination enclosure is using metal bus bars, which came with the equipment, thus are rated for 600 amps, so you cannot use the size of them either.

But another question: 10,000 sf house and only 300 amps?

Thanks for the response., but when you say 300amps for a 10,000 sf house I'm confused. What about the 200 Amp breaker below the 3 100 amp breaskers?

Originally Posted by Stephen G Sheldon

Thanks for the response., but when you say 300amps for a 10,000 sf house I'm confused. What about the 200 Amp breaker below the 3 100 amp breaskers?

Because, each time I read your post I skipped the 200 amp breaker and went to the " single pole unlabeled breaker below it" ... oops.

500 amps sounds much more logical, albeit on the lower side, of what I've seen on houses that size. Most were 600 amps and up -way up from there.

Thanks, Jerry.

What is the rating of the meter?

Did you take of the panel cover to inspect inside?

Originally Posted by Jerry Peck

To answer your question, though, no, you cannot simply add up the separate main disconnects (maximum of 6) to determine the service size, and the rating on the equipment is simply the maximum rating use allowed.

I never realized the 6 throws of the hand rule was still in use for anything. Is this a standard still for any/all panels as you work up from a basic residential service?

Originally Posted by Matt Fellman

I never realized the 6 throws of the hand rule was still in use for anything. Is this a standard still for any/all panels as you work up from a basic residential service?

Actually, the old standard was one disconnect. The 6 came in as an exception for dwelling units a few decades ago (I looked it up recently and posted it here, don't remember when it was) and then worked its way out of an exception for dwelling into being applicable for all installation.

For some time now that maximum of 6 has had several exemptions:
From the 2008 NEC. (underlining is mine)
- 230.71 Maximum Number of Disconnects.
- - (A) General. The service disconnecting means for each service permitted by 230.2, or for each set of service-entrance conductors permitted by 230.40, Exception No. 1, 3, 4, or 5, shall consist of not more than six switches or sets of circuit breakers, or a combination of not more than six switches and sets of circuit breakers, mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard. There shall be not more than six sets of disconnects per service grouped in any one location.
- - - For the purpose of this section, disconnecting means installed as part of listed equipment and used solely for the following shall not be considered a service disconnecting means:
- - - - (1) Power monitoring equipment
- - - - (2) Surge-protective device(s)
- - - - (3) Control circuit of the ground-fault protection system
- - - - (4) Power-operable service disconnecting means
- - (B) Single-Pole Units. Two or three single-pole switches or breakers, capable of individual operation, shall be permitted on multiwire circuits, one pole for each ungrounded conductor, as one multipole disconnect, provided they are equipped with identified handle ties or a master handle to disconnect all conductors of the service with no more than six operations of the hand.
- - - FPN: See 408.36, Exception No. 1 and Exception No. 3, for service equipment in certain panelboards, and see 430.95 for service equipment in motor control centers.

- 230.72 Grouping of Disconnects.
- - (A) General. The two to six disconnects as permitted in 230.71 shall be grouped. Each disconnect shall be marked to indicate the load served.
- - - Exception: One of the two to six service disconnecting means permitted in 230.71, where used only for a water pump also intended to provide fire protection, shall be permitted to be located remote from the other disconnecting means.
- - (B) Additional Service Disconnecting Means. The one or more additional service disconnecting means for fire pumps, emergency systems, legally required standby, or optional standby services permitted by 230.2 shall be installed remote from the one to six service disconnecting means for normal service to minimize the possibility of simultaneous interruption of supply.
- - (C) Access to Occupants. In a multiple-occupancy building, each occupant shall have access to the occupant’s service disconnecting means.
- - - Exception: In a multiple-occupancy building where electric service and electrical maintenance are provided by the building management and where these are under continuous building management supervision, the service disconnecting means supplying more than one occupancy shall be permitted to be accessible to authorized management personnel only.

Thus, the hard and fast rule of not more than 6 disconnects is not hard and fast ... however, when dealing with dwelling units, it is highly unlikely that you will find a service disconnect which exceeds 6 and meets the above requirements.

It is not uncommon, in larger homes, to find 2, 3, 4, 5 disconnects within the same enclosure and which feed separate panels in the house.

From another forum "I was fortunate enough to know one of the members of Code-making panel 4 responsible for writing the rules for services when this rule was introduced. His name was Lou Lafleur (spelling ??) He was also executive director of IAEI many years ago. I asked him the question, where did the number 6 come from? He said that with the new appliance coming available, we started with a single 30 amp knife-blade disconnect to disconnect the two 30 amp edision base main fuses. As the load increased for the service load we kept adding additional knife-blade disconnects and fuses. Finally the committee said enough is enough and set the limit to 6. There was no technical reason offered at that time other than it was getting unwieldly. "