If you are planning to wire a house or building, there are many
things to consider. The size of the service, the number of single pole
(120 volt) circuits, the number of two pole (240 volt) circuits, and
many other things.

        To determine the size of the service, you need to know how
many circuits there are and what the load is for them, therfore the
service entrance is the last thing to determine.

        Basically the average sized residence will require a 100 amp
service, if the home has gas appliances such as heat, water heater,
and cookstove. A home with all electric appliances usually requires
a 200 amp service. Article 220 of the NEC gives the requirements for
computing the loads. Also look under Electrical Circuits for these
rules and formulas.
        
        Article 230-79 of the NEC states that for a one family dwelling, 
the service disconnecting means shall have a rating of not less than 
100 amperes, 3-wire under either of the following conditions: (1) where 
the initial computed load is 10 kva or more, or (2) where the initial 
installation consists of six or more 2-wire branch circuits. 

(d) All other installations the service disconnecting means shall have a 
rating of not less than 60 amperes.

        The service disconnecting means shall have a rating not less
than the load to be carried, determined in accordance with article 220.

        Article 230-71 states that the service disconnecting means for
each service permittec by 230-2, or for each set of service-entrance
conductors permitted by 230-40, shall consist of not more than six
switches or circuit breakers mounted in a single enclosure, in a group
of separate enclosures, or in a switchboard. There shall be no more than
six disconnects per service grouped in any one location. This means that
you can use up to six breakers or switches as disconnects without a single
main disconnect. More than six requires a main disconnect.
        Article 230-82 states that equipment shall not be connected to
the supply side of the service disconnecting means, except for exceptions
1 thru 8.

        Other than load requirements, the mechanical installation also
has it's rules. There should be sufficient working space in the area of 
the service entrance and all live parts shall be enclosed, see Article
230-64 thru 230-65, which gives the particulars including a table which
specifies that the minumum clearance for 0-150 volts, under conditions
1,2, and 3 measured from the front of the panel, or if exposed, the front
of the live parts, is to be 3 feet. 151 to 600 volts under condition 1 is
to be 3 feet, condition 2, 3 1/2 feet, and under condition 3, 4 feet. 

        Article 230-54 states, service raceways (entrances) shall be
equipped with a raintight service head, formed in a gooseneck arrangement
to prevent the entrance of moisture. Service heads and drip loop shall
be above the service drop attachment not farther than 24 inches.

        The service should be installed so that the service drop is not
less than 10 feet from the ground, 12 feet from a residence driveway or
18 feet above a commercial drive and 22 feet above a street.

        The service attachment shall be at least 18 inches from the roof
line 24 inch max and no more than 24 inches max from the service head.

        The raceway (conduit), when penetrating the roof, should be 2 inch
rigid or i.m.c. conduit.
        
        The meter on a residence should be of a height 5 to 6 feet to
the center from the ground.
        
        The ground wire should be, a min # 8 copper unprotected and the
the ground rod 5/8 inch by 8 feet.

The minimum size equipment grounding conductors for grounding raceway
and equipment as determined by the overcurrent device in amperes:
		        Copper wire
		Amperes   Size
		********|********
		   15   |  14
		   20   |  12
		   30   |  10
		   40   |  10
		   60   |  10
		  100   |   8
		  200   |   6
		  300   |   4
		  400   |   3
		  500   |   2
		  600   |   1
		  800   |  1/0
		 1000   |  2/0
		 1200   |  3/0
		 1600   |  4/0
		 2000   |  250 mcm
		 2500   |  350 mcm
		 3000   |  400 mcm
		 4000   |  500 mcm
		 5000   |  700 mcm
		 6000   |  800 mcm


        The ground wire can be enclosed in conduit, but the conduit must
be solidly connected to the ground rod and the other end. Grounding shall be in accordance
with Article 250, parts B,C,D,F,G,H and J.

	The disconnecting means shall be nearest the point of entrance
of the service conductors at a readily accessible location either inside
or outside of the building. Outside disconnects must be raintight and no 
more than six inside or out. 

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