two family dwelling

[george t. everett]

A two family dwelling unit service is supplied underground to a two meter inclosure. Unit one has a panel directly behind the meter. Unit two is supplied underground from meter to a main panel 30' away. Is this installation OK or do the disconnects need to be grouped together? There is no firewall between units.

 

[pierre]

Re: two family dwelling

George

Since you mention there is no firewall, this is one building and the service disconnects need to be 'grouped' together [230.72(A)]. The NEC does not have a measurement for this, but for the safety of an unsuspecting fireman, they should be relatively close together, with each marked to indicate which load it serves.

Pierre

 

[david]

Re: two family dwelling

230.40 Number of Service-Entrance Conductor Sets.
Each service drop or lateral shall supply only one set of service-entrance conductors.
Exception No. 1: A building with one or more than one occupancy shall be permitted to have one set of service-entrance conductors for each service of different characteristics, as defined in 230.2(D), run to each occupancy or group of occupancies.


I do not see any thing wrong with the Installation as you described it. As long as your service entrance conductor is considered out side of the building and the service entrance goes to the a service disconnect that consist of no more than six throws of the hand grouped in any one location.

You may need to check with your building department to see if this building is in fact a two family dwelling. If there is no problem with the building code, I do not see the NEC having a problem with this.

[ August 30, 2003, 02:03 PM: Message edited by: david ]

 

[websparky]

Re: two family dwelling

Hi David,

Here the basic rule is stated.

2002 NEC 230.40 Number of Service-Entrance Conductor Sets.
Each service drop or lateral shall supply only one set of service-entrance conductors.

The exception you are quoting referes to "each service of different characteristics, as defined in 230.2(D)".

When we read 230.2(D), it states;

(D) Different Characteristics. Additional services shall be permitted for different voltages, frequencies, or phases, or for different uses, such as for different rate schedules.

This exception does not apply here. However,exception 2 does allow for separate meters and disconnecting means:

Exception No. 2: Where two to six service disconnecting means in separate enclosures are grouped at one location and supply separate loads from one service drop or lateral, one set of service-entrance conductors shall be permitted to supply each or several such service equipment enclosures.

For the original question, exception 2 does permit separate loads. However, there needs to be separate disconnecting means also at this location. If there is, George didn't mention it.

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 Nos. 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 no more than six sets of disconnects per service grouped in any one location...........

As far as the NEC is concerned, a fire wall does not come into consideration.

 

[david]

Re: two family dwelling

Commentary NEC hand book: 230.40
Each set of service-drop or service-lateral conductors is allowed to supply only one set of service-entrance conductors. However, if a service drop or a service lateral supplies a building with more than one occupancy, such as multifamily dwellings, strip malls, and office buildings, each service drop or service lateral is allowed to supply more than one set of service-entrance conductors, provided they are run to each occupancy or group of occupancies.

__________________________________________________
This exception does not apply here. However,exception 2 does allow for separate meters and disconnecting means:
__________________________________________________

websparky

Why do you say the exception does not apply to a two family dwelling with a two meters enclosure?

[ August 30, 2003, 05:26 PM: Message edited by: david ]

 

[don_resqcapt19]

Re: two family dwelling

websparky,
I believe that Exception #1 to 240.30 does apply here. The reference to 230.2(D) just means that each occupancy can have a service for each of the different characteristics. In this case all of the services have the same characteristics, so Exception #1 permits each occupancy to have one service. There is no code requirement that the disconnects for these services be grouped. The requirement in 230.70(A) only requires that where a service has multiple disconnects, that these disconnects be grouped. It does not require that the disconnects for multiple occupancies in a common building be grouped.
Don

 

[david]

Re: two family dwelling

(D) Different Characteristics. Additional services shall be permitted for different voltages, frequencies, or phases, or for different uses, such as for different rate schedules.

Wouldn?t a service entrance coming off a meter to the first occupancy be a different use from a service entrance fed from a second meter to a second occupancy?

Do you consider two meters to two separate loads to be the same rate schedule?

 

[websparky]

Re: two family dwelling

David, Don and .et all,

My apologies.

I had my head elsewhere and should have read the post more carefully . This installation is allowed.

Exception #1 still makes me think of different voltages and phases.

Well, the good part about these mindless moments is it makes us all look again and learn a little more!

Thanks,
Dave

 

[pierre]

Re: two family dwelling

I am respectfully disagreeing with some comments here.

230.40 Exception 1 - this is for services of different characteristics, such as voltage, phases, etc... .
I believe multiple occupancies means different types of occupancies such as a retail, offices and dwellings in the same structure (building). these different type of occupancies may require different types of services (I am not suggesting you are not aware of this, just mentioning it to substantiate what I am trying to say).
The NEC specifically uses the terms - single family, two family, and multifamily dwellings in Article 100(not to be confused with multiple type occupancies).

230.2 permits one service to a building, unless conditions exist as in 230.2(A) through (D). I do not see any of these conditions in the question that was asked.

There are many single family dwellings that have been converted to two family dwellings,usually without firewalls. This question specifically says there is no firewall separating the two family, so it is considered as one building (definition of building, Article 100). I am not saying that two sets of service entrance conductors cannot be installed, just that these two disconnects need to be grouped together.

Pierre

 

[bennie]

Re: two family dwelling

If the switch for the first unit is inside, and the switch for the second unit is outside, would this constitute being grouped?

What is the reason for grouping the switches?

 

[david]

Re: two family dwelling

__________________________________________________
I believe multiple occupancies means different types of occupancies such as a retail, offices and dwellings in the same structure (building). these different type of occupancies may require different types of services (I am not suggesting you are not aware of this, just mentioning it to substantiate what I am trying to say).
__________________________________________________

Pierre

Are you saying for a building to have more than one occupant it has to be for example a residence in part and an office in the other part?

Are you saying a building with two dwellings is not a multiple occupancy building?

 

[david]

Re: two family dwelling

230.70 General.
Means shall be provided to disconnect all conductors in a building or other structure from the service-entrance conductors.
(A) Location. The service disconnecting means shall be installed in accordance with 230.70(A)(1), (2), and (3).

Bennie,

I believe you are allowed to group up to six service disconnects instead of a single service disconnect.

I heard you comment may times that the group of disconnects is limited to a max of six, to limit the available fault current on any one service. You seem to drive home the point that this is not for the firemen to have ready access. You have stated in the past the firemen will wait for the utility to pull the cut out to insure the power s disconnected.

 

[bennie]

Re: two family dwelling

Not many agree with me, but I have always understood that the six disconnect limit was to keep power on, not turn it off. Of course it can be turned off, that is a fact, but not the prime reason.

One item of equipment can short or ground out and trip the overcurrent device, leaving the rest of the system in operation.

Inrush current, after a power outage, is easier to deal with when there is six paths for the current to divide.

Grouping of disconnects, and being close to the entry point, is to limit the amount of unfused conductor exposure on the inside of a dwelling or structure.

Some firemen are allowed to turn off power, in other areas they are not. This is due to the service remaining energized on the line side.

 

[charlie]

Re: two family dwelling

FYI, the official interpretation in Indiana (the Indiana State Building Commission is the final word here) is that the disconnecting means are not required to be grouped because the disconnecting means are in different occupancies.

The same applies to strip centers. Each occupancy is permitted to have up to six disconnects in his own unit grouped together. If a strip center wishes to put a disconnect under each meter, the maximum is six without a main in front of some to limit the total to six at any one location.

With that said, I am sure other jurisdictions will interpret this differently.