Electric Clothes Dryer Load

Table 3-3 (NEC@, table 220-18) shows the demand factors that may be applied to electric clothes dryers. For the wattage of the dryer, use the rating given on the nameplate or 5,000 watts, Number of Demand Factor Dryers Percent whichever is larger. All dryers rated less than 5 kilowatts must be figured at 5 kilowatts. It is rare that a dwelling will have more than four clothes dryers, so a loo-percent demand factor is used in most cases.

Reprinted with permission from NPFA 70-1990, the National Electrical CodeR, Copyrightc1989, National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association, on the referenced subject which is represented only by the standard in its entirety.

Electric Range Load

The demand load for electric ranges, wallmounted ovens, and counter-mounted cooking units is defined in table 3-4 (NECR, table 220-19). You must know the nameplate rating (in kilowatts) before you can determine the demand factor. Use column A of table 3-4 for appliance ratings of 9 to 12 kilowatts. The demand factor has already been calculated for you and is expressed in kilowatts, depending on the number of appliances on a branch circuit. Column B is used for appliances rated less than 3 1/2 kilowatts, and column C is for appliances rated 3 1/2 kilowatts to 8 3/4 kilowatts. Both columns are

Table 3-4.\Demand Loads for Household Electric Ranges, Wall-Mounted Ovens, Counter-Mounted Cooking Units, and Other Household Cooking Appliances Over 1 3/4 kW Rating

(Column A to be used in all cases except as otherwise permitted in Note 3 below.)

Note 1. Over 12 kW through 27 kW ranges all of same rating. For ranges individually rated more than 12 kW but not more than 27 kW, the maximum demand in Column A shall be increased 5 percent for each additional kW of rating or major fraction thereof by which the rating of individual ranges exceeds 12 kW.

Note 2. Over 8 3/4 kW through 27 kW ranges of unequal ratings. For ranges individually rated more than 8 3/4 kW and of different ratings but none exceeding 27 kW, an average value of rating shall be computed by adding together the ratings of all ranges to obtain the total connected load (using 12 kW for any range rated less than 12 kW) and dividing' by the total number of ranges; and then the maximum demand in Column A shall be increased 5 percent for each kW or major fraction thereof by which this average value exceeds 12 kW.

Note 3. Over 1 3/4 kW through 8 3/4 kW. In lieu of the method provided in Column A, it shall be permissible to add the nameplate ratings of all ranges rated more than 1 3/4 kW but not more than 8 3/4 kW and multiply the sum by the demand factors specified in Column B or C for the given number of appliances.

Note 4. Branch-Circuit Load. It shall be permissible to compute the branch-circuit load for one range in accordance with Table 220-19 in the National Electrical Code^R. The branch-circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be computed by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range.expressed as a percentage of nameplate rating, depending on the number of appliances on a branch circuit.

Note 5. This table also applies to household cooking appliances rated over 1 3/4 kW and used in instructional programs.

Reprinted with permission from NPFA 70-1990, the National Electrical Code^R, Copyright^c1989, National Fire Protection Association, Quincy, MA 02269. This reprinted material is not the complete and official position of the National Fire Protection Association, on the referenced subject which is represented only by the standard in its entirety.