Master Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsHard
A master electrician is installing a new X-ray machine in a hospital operating room. According to NEC, what is the minimum branch-circuit rating for a single X-ray unit, unless otherwise specified by the manufacturer?
- A40 amperes
- B30 amperes
- C20 amperes
- D15 amperes
Show answer & explanationAnswer & explanation
Correct answer: B. 30 amperes
NEC Section 517.73(A) specifies that a branch circuit for a single X-ray unit shall have a minimum rating of 30 amperes, unless otherwise specified by the manufacturer. This ensures adequate capacity for the high momentary loads typical of X-ray equipment.
Why the other options are wrong
- A. 40 amperes is higher than the minimum specified by NEC, though it might be required by a specific manufacturer.
- C. 20 amperes is common for general purpose receptacles but inadequate for the specialized demands of X-ray equipment.
- D. 15 amperes is typically for general lighting or receptacle circuits, insufficient for X-ray units.
X-ray Unit Branch Circuit Rating
The minimum ampere rating required by the NEC for branch circuits supplying a single X-ray unit in health care facilities, to ensure safe and reliable operation.
- Applies to single X-ray units.
- NEC 517.73(A) governs this.
- Manufacturer's specifications can override the minimum.
Memory trick: X-ray circuits, minimum thirty, for patient safety, don't be dirty!