A case study of main service short time demand intervals

Section 220-36 of the 1990 National Electrical Code is an optional method to calculate the the service entrance and main panel size for new restaurants. When Section 220-36 is used for design it frequently results in smaller service entrance and main panel sizes than the “standard or conventional” method. Cost studies have shown that about two-thirds of all new restaurants could use Section 220-36 and experience construction cost savings of $3000 to $30000. Several restaurant chains have utilized the new article in the design and construction of their their new restaurants. There have been no reported problems related to the use of Section 220-36 in those restaurants that have been built using that section of the code. Some electrical engineers and others have speculated that since use of NEC 220-36 will result in smaller service sizes, a restaurant may experience nuisance tripping. This is likely to happen, it is theorized, when the restaurant opens for the day and all the food preparation equipment is turned on. This article reports the results of a case study showing that nuisance tripping is not likely to be an issue