Omission of overcurrent is permitted at points where busways are reduced in size, provided that the smaller busway length does not exceed what distance?

• A. 10 ft
• B. 20 ft
• C. 30 ft
• D. 50 ft

Answer: (D)

When a busway is reduced to a smaller cross-section, you can sometimes omit an overcurrent protection device in that downstream portion. The reason this is allowed is to simplify installation while still keeping protection effective: any fault in that short, smaller section must be cleared by the upstream protective device within its time frame. To ensure safety and fault control, the length of the unprotected, smaller busway is limited.

That limit is 50 feet. If the shortened section were longer than 50 feet, you would need to provide overcurrent protection in that smaller busway instead of omitting it.