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#Grounding electrode conductor sizing code#

For application of this section, the main power feeder shall be the feeder between the main disconnect and the panelboard that supplies, either by branch circuits or by feeders, or both, all loads that are part or associated with the dwelling unit. For individual dwelling units of one-family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(7), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit and are installed in raceway or cable with or without an equipment grounding conductor. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).ģ10.15(B)(7) 120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders.

#Grounding electrode conductor sizing code#

See the actual NEC ® text at NFPA.ORG for the complete code section.

Take 83 amps and use the 75☌ column in Table 310.15(B)(16) to determine that the service requires 4 AWG copper, type THWN overhead service entrance conductors.Ī close look at the old deleted table shows the same results.īelow is a preview of the NEC ®.

This is the minimum required service conductor.

A 100 amp electrical service will be used to supply the 98 amp load for the single family dwelling.

In the 2014 NEC ®, the table has been deleted and replaced with a simple 83% which results in the same final value as if the table had just been allowed to remain.Įxample: A 120/240-Volt, 3-Wire, single-phase electrical service for a single family dwelling with a calculated load (from Article 220) of 98 amps, supplied by THWN copper overhead service entrance conductors. To use the table, one would first determine the minimum size service or feeder by using the load calculations in Article 220 and then select the minimum size conductor from Table 310.15(B)(7).

In the 2011 NEC ®, a simple table existed showing the service size on the left and the minimum size conductor required to supply the service on the right. Section 310.15(B)(7) contains rules on calculating the conductor size for 120/240-volt, 3-wire, single-phase dwelling services and feeders. Code Change Summary: Table 310.15(B)(7) has been deleted and replaced with an 83% calculation.