For a 200-amp load facility used for feeding charging tools that is around 400 ft from main switchboard, what size of bonding cable is required? — T. C.

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The question shows up to address a voltage-drop situation, however information is missing. I will answer the inquiry by inserting the minimum crucial information. The very first item to clarify is the terminology. Ns presume you room referring to the size of the devices grounding conductor through the feeder and not a bonding wire which is undefined by the NEC. The next bit of details needed is the dimension of the ungrounded phase conductors intended come be installed for this feeder. Note: if a voltage-drop calculation is performed because that this 400-ft feeder, climate the mechanism voltage and phase construction of the feeder are essential for the voltage-drop calculation. I will answer the question without the voltage-drop calculate information since this info is missing.

First, the question is restructured as follows:

What is the minimum size equipment grounding conductor required for a feeder (400 feet in length) giving a panelboard because that charging equipment?

For a 200-ampere feeder, a 3/0 copper conductor is generally required by the minimum requirements of the NEC. The minimum size equipment grounding conductor forced for a 200-ampere feeder is not less than 6 AWG copper (see 250.122 and also Table 250. 122). Currently if the feeder ungrounded conductors have been enhanced in dimension from 3/0 copper to 250 kcmil copper (for example) for voltage fall reasons, then the required devices grounding conductor must additionally be enhanced in dimension proportionately . This is done as follows using Table 8, thing 9 the the NEC:

Using Table 8, chapter 9Required size 3/0 AWG = 167,800 cmAdjusted dimension 250 kcmil = 250,000 cm

Adjusted size phase conductor ÷ forced phase conductor dimension = 250,000 ÷ 167,800 = 1.49The multiplier is 1.49. The size of the ungrounded circuit conductors has actually been raised 149%; therefore, the equipment grounding conductors should be boosted 149% together well, per 250.122(B).

Required tools grounding conductor = 6 AWG copper (Table 250.122 based on 200 ampere overcurrent defense for the feeder)

Using Table 8, thing 96 AWG = 26,240 cm × 1.49 = 39,097.6 cm

According to Table 8, a 4 AWG copper is required = 41,740 cm

The minimum size tools grounding conductor for this 200-ampere feeder is a 4 AWG copper conductor. The answer is based upon NEC-2008, sections 250.122, Table 250.122, and also Chapter 9, Table 8 (conductor properties).

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I expect this helps through you questions concerning sizing equipment grounding conductors because that feeders. Together always, top the neighborhood authority having jurisdiction for any type of local electric code rule that may be essential in addition to the minimum requirements of the NEC. — Michael J. Johnston, CMP-5


Michael Johnston is NECA’s executive, management director that standards and safety. Prior to his place with NECA, Mike to be director of education and learning codes and also standards for IAEI. Mike hold a BS in business Management from the university of Phoenix. Mike is the chairman that the NEC Correlating Committee. He served on NEC CMP-5 in the 2002, 2005, and chair the CMP-5 representing NECA for the 2011 NEC cycle. Among his responsibilities for controlling the codes, standards, and also safety functions for NECA, Mike is secretary of the NECA Codes and Standards Committee. Johnston is a member that the IBEW and is an energetic member the ANSI, IAEI, NFPA, SES, ASSE, ANSI-EVSP and ANSI-ESSCC, and the UL electrical Council, the national Safety Council and also vice chair that the NFPA electric Section.