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- Location
- USA
- Occupation
- Electrician
Article 220 load calculation question:
Given single 8 kW ranges in all units in a multifamily dwelling, does one use the Table 220.55 Column C kW demand or apply the Column B demand factor percentages?
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The heading for Table 220.55 reads:
(Column C to be used in all cases except as otherwise permitted in Note 3.)
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Table 220.55 Note 3:
Over 1-3∕4 kW through 8-3∕4 kW. In lieu of the method provided in Column C, it shall be permissible to add the nameplate ratings of all household cooking appliances 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 A or Column B for the given number of appliances. Where the rating of cooking appliances falls under both Column A and Column B, the demand factors for each column shall be applied to the appliances for that column, and the results added together.
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The 2017 Handbook commentary:
The values in Column C are applicable to installations where all ranges in the group have the same rating. Note 1 applies where the ranges are rated greater than 12 kilowatts and Note 2 applies where the ranges in a group have different ratings. Column C must be used unless Note 3 is applicable. Notes 3 and 4 cover installations where the circuit supplies multiple cooking components, which are combined and treated as a single range.
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The 2017 Handbook commentary:
Table Note 3. For a group installation of ranges with ratings between 1-3⁄4 kilowatts through 8-3⁄4 kilowatts, the ratings are permitted to be added together for determining a demand factor. Ranges rated below 3-1⁄2 kilowatts should be grouped independently of those rated 3-1⁄2 kilowatts and above. The appropriate column (A or B) is used rather than Column C.
Calculation Example
Determine the maximum demand for 4 ranges rated at 4.5 kW, 5 kW,
5 kW, and 8.5 kW, respectively.
Solution
Step 1. Combine ratings into single value: 4.5 kW + 5 kW + 5 kW + 8.5 kW = 23 kW
Step 2. Determine demand factor: 50% (Column B, 4 ranges)
Step 3. Calculate the maximum demand: 23 kW × 50% = 11.5 kW
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Attached are two charts plotting the Column C VA value along with applying the Column B demand factors to six similar VA values.
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Given single 8 kW ranges in all units in a multifamily dwelling, does one use the Table 220.55 Column C kW demand or apply the Column B demand factor percentages?
________________________________________
The heading for Table 220.55 reads:
(Column C to be used in all cases except as otherwise permitted in Note 3.)
________________________________________
Table 220.55 Note 3:
Over 1-3∕4 kW through 8-3∕4 kW. In lieu of the method provided in Column C, it shall be permissible to add the nameplate ratings of all household cooking appliances 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 A or Column B for the given number of appliances. Where the rating of cooking appliances falls under both Column A and Column B, the demand factors for each column shall be applied to the appliances for that column, and the results added together.
________________________________________
The 2017 Handbook commentary:
The values in Column C are applicable to installations where all ranges in the group have the same rating. Note 1 applies where the ranges are rated greater than 12 kilowatts and Note 2 applies where the ranges in a group have different ratings. Column C must be used unless Note 3 is applicable. Notes 3 and 4 cover installations where the circuit supplies multiple cooking components, which are combined and treated as a single range.
________________________________________
The 2017 Handbook commentary:
Table Note 3. For a group installation of ranges with ratings between 1-3⁄4 kilowatts through 8-3⁄4 kilowatts, the ratings are permitted to be added together for determining a demand factor. Ranges rated below 3-1⁄2 kilowatts should be grouped independently of those rated 3-1⁄2 kilowatts and above. The appropriate column (A or B) is used rather than Column C.
Calculation Example
Determine the maximum demand for 4 ranges rated at 4.5 kW, 5 kW,
5 kW, and 8.5 kW, respectively.
Solution
Step 1. Combine ratings into single value: 4.5 kW + 5 kW + 5 kW + 8.5 kW = 23 kW
Step 2. Determine demand factor: 50% (Column B, 4 ranges)
Step 3. Calculate the maximum demand: 23 kW × 50% = 11.5 kW
________________________________________
Attached are two charts plotting the Column C VA value along with applying the Column B demand factors to six similar VA values.
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