A master electrician is performing a service load calculation for a commercial office building. The building has a total connected general lighting load of 50,000 VA and a noncontinuous receptacle load of 15,000 VA. What is the total calculated demand load, assuming no other loads and a 120/208V, three-phase system?
- A40,000 VA
- B65,000 VA
- C50,000 VA
- D45,000 VA
Show answer & explanationAnswer & explanation
Correct answer: B. 65,000 VA
According to NEC 220.40, for service loads, general lighting and receptacle loads are typically summed without additional demand factors for these specific categories unless otherwise specified. For commercial buildings, general lighting is usually taken at 100% unless a specific demand factor (like for continuous loads) applies. Noncontinuous receptacle loads are also taken at 100% unless covered by specific demand factor rules (like NEC 220.44 for general-purpose receptacles). Since no other demand factors are mentioned, these loads are simply added: 50,000 VA + 15,000 VA = 65,000 VA.
Why the other options are wrong
- A. This option results from applying an incorrect demand factor to both loads.
- C. This option incorrectly ignores the receptacle load or applies an incorrect demand factor.
- D. This option results from applying an incorrect demand factor to one or both loads.
Commercial General Load Summation
For commercial buildings, general lighting and noncontinuous receptacle loads are typically summed at 100% of their connected values for service calculations, unless specific NEC demand factors (e.g., for continuous loads or a high number of receptacles) are applicable.
- General lighting load is usually 100% demand.
- Noncontinuous receptacle loads are usually 100% demand.
- Always check for specific NEC sections (e.g., 220.42, 220.44) that might allow demand factors.
Memory trick: Commercial: Light and plugs, just add them up!