Journeyman Electrician Exam (NEC)General Electrical Knowledge and Plan ReadingHard
A client is planning a new commercial kitchen. The blueprints indicate a 3-phase, 4-wire, 208Y/120V service. A significant part of the load consists of cooking equipment. What type of load calculation method is generally used for commercial kitchens under the NEC?
- AStandard method (100% of connected load).
- BDemand factors specified in NEC Article 220, Part III, for commercial cooking equipment.
- CFeeder and service load calculations per NEC Article 220, Part II, for general loads.
- DOptional method (using 220.82).
Show answer & explanationAnswer & explanation
Correct answer: B. Demand factors specified in NEC Article 220, Part III, for commercial cooking equipment.
For commercial cooking equipment, the NEC provides specific demand factors in Article 220, Part III (specifically 220.56). These demand factors allow for a reduction in the calculated load due to the intermittent nature of operation of multiple pieces of equipment, which is critical for correctly sizing feeders and services in commercial kitchens.
Why the other options are wrong
- A. The standard method at 100% is rarely used for large commercial loads due to diversity, leading to oversized conductors/OCPDs.
- C. Part II covers general feeder and service calculations, but for specific equipment like commercial cooking, Part III provides more specialized and often lower demand factors.
- D. The optional method (220.82) is primarily for dwelling units and farm buildings, not commercial kitchens.
NEC Commercial Cooking Demand Factors
The National Electrical Code (NEC) provides specific demand factors in Article 220, Part III (Table 220.56) for calculating the feeder and service loads of commercial cooking equipment, acknowledging their diverse and intermittent use.
- Reduces the calculated load for multiple appliances.
- Prevents oversizing of electrical infrastructure.
- Based on the number of units and their ratings.
- Crucial for cost-effective and safe design of commercial kitchens.
Memory trick: General, Optional, or Specific Demand.