Code Quiz

Jan. 7, 2005
In a newly designed multi-family dwelling unit (208/120V, 3-phase, 4-wire system) the calculated load on the service grounded “neutral” conductor is calculated to be 475A. What is the demand load, if any, on the grounded “neutral” conductor of this ...

In a newly designed multi-family dwelling unit (208/120V, 3-phase, 4-wire system) the calculated load on the service grounded “neutral” conductor is calculated to be 475A. What is the demand load, if any, on the grounded “neutral” conductor of this system?

A) 392.5A
B) 200A
C) 475A
D) 406.25A

Answer: A)

Explanation: Article 220 has been reorganized in the 2005 NEC. Sec. 220.61(B)(2) allows a demand factor of 70% to be applied on that portion of the neutral load that exceeds 200A as long as the neutral load doesn’t consist primarily of nonlinear loads, which are harmonic in nature. A reduction isn’t permitted on the first 200A, but the 70% demand factor is allowed for the amount exceeding 200A.

475A – 200A = 275A
275A x 70% = 192.5A
192.5A + 200A = 392.5A

Owen is the owner and president of National Code Seminars and the holder of master electrician certifications in 46 states. He can be reached at [email protected].

About the Author

Steven Owen

Voice your opinion!

To join the conversation, and become an exclusive member of EC&M, create an account today!

Sponsored Recommendations

Electrical Conduit Comparison Chart

CHAMPION FIBERGLASS electrical conduit is a lightweight, durable option that provides lasting savings when compared to other materials. Compare electrical conduit types including...

Don't Let Burn-Through Threaten Another Data Center or Utility Project

Get the No Burn-Through Elbow eGuide to learn many reasons why Champion Fiberglass elbows will enhance your data center and utility projects today.

Considerations for Direct Burial Conduit

Installation type plays a key role in the type of conduit selected for electrical systems in industrial construction projects. Above ground, below ground, direct buried, encased...

How to Calculate Labor Costs

Most important to accurately estimating labor costs is knowing the approximate hours required for project completion. Learn how to calculate electrical labor cost.