Page 727 - 2018_IRC

SERVICES

TABLE E3602.2 E3603.1.1 Ungrounded service conductors. For a service
MINIMUM SERVICE LOAD CALCULATION [220.82(B) & (C)] rated at 100 through 400 amperes, the service conductors
LOADS AND PROCEDURE supplying the entire load associated with a one-family
3 volt-amperes per square foot of floor area for general lighting dwelling, or the service conductors supplying the entire
and general use receptacle outlets. load associated with an individual dwelling unit in a two-
Plus family dwelling, shall have an ampacity of not less than 83
percent of the service rating. The service rating is based on
1,500 volt-amperes multiplied by total number of 20-ampere-rated
small appliance and laundry circuits. the standard ampere ratings in Section E3705.6.
Plus E3603.1.2 Ungrounded feeder conductors. For a feeder
rated at 100 through 400 amperes, the feeder conductors
The nameplate volt-ampere rating of all fastened-in-place, supplying the entire load associated with a one-family
permanently connected or dedicated circuit-supplied appliances dwelling, or the feeder conductors supplying the entire load
such as ranges, ovens, cooking units, clothes dryers not
connected to the laundry branch circuit and water heaters. associated with an individual dwelling unit in a two-family
Apply the following demand factors to the above subtotal: dwelling, shall have an ampacity of not less than 83 percent
of the feeder rating. The feeder rating is based on the stan-
The minimum subtotal for the loads above shall be 100 percent of dard ampere ratings in Section E3705.6.
the first 10,000 volt-amperes of the sum of the above loads plus
40 percent of any portion of the sum that is in excess of 10,000 E3603.1.3 Feeder size relative to service size. A feeder
volt-amperes. for an individual dwelling unit shall not be required to
have an ampacity greater than that specified in Sections
Plus the largest of the following:
E3603.1.1 and E3603.1.2.
One-hundred percent of the nameplate rating(s) of the air-
conditioning and cooling equipment. E3603.1.4 Grounded conductors. The grounded conduc-
tor ampacity shall be not less than the maximum unbal-
One hundred percent of the nameplate rating(s) of the heat pump ance of the load and the size of the grounded conductor
where a heat pump is used without any supplemental electric
heating. shall be not smaller than the required minimum grounding
One-hundred percent of the nameplate rating of the electric electrode conductor size specified in Table E3603.4.
[310.15(B)(7)]
thermal storage and other heating systems where the usual load
is expected to be continuous at the full nameplate value. Systems E3603.1.5 Adjustment/correction factors. Where cor-
qualifying under this selection shall not be figured under any rection or adjustment factors are required by Section
other category in this table. E3705.2 or E3705.3, they shall be permitted to be applied
One-hundred percent of nameplate rating of the heat pump to the ampacity associated with the temperature rating of
compressor and sixty-five percent of the supplemental electric the conductor.
heating load for central electric space-heating systems. If the E3603.2 Ungrounded service conductors for accessory
heat pump compressor is prevented from operating at the same
time as the supplementary heat, the compressor load does not buildings and structures. Ungrounded conductors for other
need to be added to the supplementary heat load for the total than dwelling units shall have an ampacity of not less than 60
central electric space-heating load. amperes and shall be sized as required for feeders in Chapter
37. [230.79(D)]
Sixty-five percent of nameplate rating(s) of electric space-heating
units if less than four separately controlled units. Exceptions:
Forty percent of nameplate rating(s) of electric space-heating units 1. For limited loads of a single branch circuit, the ser-
of four or more separately controlled units. vice conductors shall have an ampacity of not less
The minimum total load in amperes shall be the than 15 amperes. [230.79(A)]
volt-ampere sum calculated above divided by 240 volts. 2. For loads consisting of not more than two two-wire
E3602.3 Rating of service disconnect. The combined rating branch circuits, the service conductors shall have an
of all individual service disconnects serving a single dwelling ampacity of not less than 30 amperes. [230.79(B)]
unit shall be not less than the load determined from Table E3603.3 Overload protection. Each ungrounded service
E3602.2 and shall be not less than as specified in Section conductor shall have overload protection. (230.90)
E3602.1. (230.79 & 230.80) E3603.3.1 Ungrounded conductor. Overload protection
E3602.4 Voltage rating. Systems shall be three-wire, 120/ shall be provided by an overcurrent device installed in
240-volt, single-phase with a grounded neutral. [220.82(A)] series with each ungrounded service conductor. The over-
current device shall have a rating or setting not higher than
the allowable service or feeder rating specified in Section
SECTION E3603 E3603.1. A set of fuses shall be considered to be all of the
SERVICE, FEEDER AND GROUNDING fuses required to protect all of the ungrounded conductors
ELECTRODE CONDUCTOR SIZING of a circuit. Single pole circuit breakers, grouped in accor-
E3603.1 Grounded and ungrounded service conductor dance with Section E3601.7, shall be considered as one
size. Service and feeder conductors supplied by a single-phase, protective device. [230.90(A)]
120/240-volt system shall be sized in accordance with Sections Exception: Two to six circuit breakers or sets of fuses
E3603.1.1 through E3603.1.4 and Table 3705.1. shall be permitted as the overcurrent device to provide

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