Mike Dolt Enterprises
Mike Dolt Enterprises
User: anbm, Location: Logan, Utah
Asked on: Monday, March 14, 2011 at 3:04 pm EDT
Answered on: Tuesday, May 14, 2024 at 2:47 am EDT
Question: We have 200A feeder fed out of 200A breaker in elec. panel, this feeder will feed 100A enclosed circuit breaker on wall, this 100A breaker is 150 feet away from panel.There is a 100A feeder from 100A breaker above to the radiology machine. (the enclosed breaker is less than 15 feet from radiology machine) Will this violate NEC tap rule or other rule? Thanks!
NEC Tap Rule
The NEC tap rule (NEC 240.21(B)) limits the rating of a tap conductor or overcurrent device to 25% of the rating of the overcurrent device protecting the feeder.
Analysis
The feeder breaker is 200A. The tap breaker is 100A. 100A is less than 25% of 200A (25% of 200A = 50A).Therefore,
the tap rule is not violated.
Other Considerations
Voltage Drop
The voltage drop in the 150-foot feeder must be calculated to ensure that the radiology machine receives sufficient voltage.
Conduit Size
The conduit size of the 100A feeder must be adequate to accommodate the conductors.
Protection Requirements
Verify that the radiology machine is properly protected by additional overcurrent devices, such as branch circuit breakers or fuses.
Conclusion:
Based on the provided information, the tap rule and other relevant NEC requirements are likely met. However, it is recommended to consult with a qualified electrician to confirm the design and ensure that all safety and code requirements are satisfied. Flag for review