MINIMUM SERVICE LOAD CALCULATION
|LOADS AND PROCEDURE|
|3 volt-amperes per square foot of floor area for general lighting and general use receptacle outlets.|
|1,500 volt-amperes multiplied by total number of 20-ampere-rated small appliance and laundry circuits.|
|The nameplate volt-ampere rating of all fastened-in-place, permanently connected or dedicated circuit-supplied appliances such as ranges, ovens, cooking units, clothes dryers not connected to the laundry branch circuit and water heaters.|
|Apply the following demand factors to the above subtotal:|
|The minimum subtotal for the loads above shall be 100 percent of 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 volt-amperes.|
|Plus the largest of the following:|
|One-hundred percent of the nameplate rating(s) of the air-conditioning and cooling equipment.|
|One hundred percent of the nameplate rating(s) of the heat pump where a heat pump is used without any supplemental electric heating.|
|One-hundred percent of the nameplate rating of the electric thermal storage and other heating systems where the usual load is expected to be continuous at the full nameplate value. Systems qualifying under this selection shall not be figured under any other category in this table.|
|One-hundred percent of nameplate rating of the heat pump compressor and sixty-five percent of the supplemental electric heating load for central electric space-heating systems. If the heat pump compressor is prevented from operating at the same time as the supplementary heat, the compressor load does not need to be added to the supplementary heat load for the total central electric space-heating load.|
|Sixty-five percent of nameplate rating(s) of electric space-heating units if less than four separately controlled units.|
|Forty percent of nameplate rating(s) of electric space-heating units of four or more separately controlled units.|
|The minimum total load in amperes shall be the |
volt-ampere sum calculated above divided by 240 volts.
SERVICE CONDUCTOR AND GROUNDING ELECTRODE CONDUCTOR SIZING
|CONDUCTOR TYPES AND SIZES-THHN, THHW, THW, THWN, USE, RHH, |
RHW, XHHW, RHW-2, THW-2, THWN-2, XHHW-2, SE, USE-2
(Parallel sets of 1/0 and larger conductors are permitted in either a single
raceway or in separate raceways)
|SERVICE OR FEEDER |
|MINIMUM GROUNDING |
ELECTRODE CONDUCTOR SIZEa
|Aluminum and copper-clad aluminum |
|Maximum load |
|2/0||4/0 or two sets of 1/0||200||4d||2d|
|3/0||250 kcmil or two sets of 2/0||225||4d||2d|
|4/0 or two sets of 1/0||300 kcmil ortwo sets of 3/0||250||2d||1/0d|
|250 kcmil or two sets of 2/0||350 kcmil or two sets of 4/0||300||2d||1/0d|
|350 kcmil or two sets of 3/0||500 kcmil or two sets of 250 kcmil||350||2d||1/0d|
|400 kcmil or two sets of 4/0||600 kcmil or two sets of 300 kcmil||400||1/0d||3/0d|
Exception: Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided that the calculated load does not exceed the ampacity of the service conductors.
CLEARANCES FROM BUILDING OPENINGS
CLEARANCES FROM ROOFS
Above-ground service-entrance cables, where subject to physical damage, shall be protected by one or more of the following: rigid metal conduit, intermediate metal conduit, Schedule 80 PVC conduit, electrical metallic tubing or other approved means.
Exception: Where it is impracticable to locate the service head or gooseneck above the point of attachment, the service head or gooseneck location shall be not more than 24 inches (610 mm) from the point of attachment.
Where the supplemental electrode is a rod, pipe or plate electrode in accordance with Section E3608.1.4 or E3608.1.5, that portion of the bonding jumper that is the sole connection to the supplemental grounding electrode shall not be required to be larger than 6 AWG copper or 4 AWG aluminum wire.
Metallic components shall be encased by at least 2 inches (51 mm) of concrete and shall be located horizontally within that portion of a concrete foundation or footing that is in direct contact with the earth or within vertical foundations or structural components or members that are in direct contact with the earth.
Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 6 feet (1829 mm) apart.
The noncurrent-carrying metal parts of the following equipment shall be effectively bonded together:
The bonding jumper shall not be smaller than the sizes shown in Table E3603.1 for grounding electrode conductors. Where the service-entrance conductors are paralleled in two or more raceways or cables, and an individual supply-side bonding jumper is used for bonding these raceways or cables, the supply-side bonding jumper for each raceway or cable shall be selected from Table E3603.1 based on the size of the ungrounded supply conductors in each raceway or cable. A single supply-side bonding jumper installed for bonding two or more raceways or cables shall be sized in accordance with Table E3603.1 based on the largest set of parallel ungrounded supply conductors.
Bare aluminum or copper-clad aluminum grounding electrode conductors shall not be used where in direct contact with masonry or the earth or where subject to corrosive conditions. Where used outside, aluminum or copper-clad aluminum grounding electrode conductors shall not be installed within 18 inches (457 mm) of the earth.
Where interior metal water piping is used as a conductor to interconnect electrodes that are part of the grounding electrode system, such piping shall be located not more than 5 feet (1524 mm) from the point of entry into the building.