Example No. D6 Maximum Demand for Range Loads

Table 220.55, Column C, applies to ranges not over 12 kW. The application of Note 1 to ranges over 12 kW (and not over 27 kW) and Note 2 to ranges over 8 3/4 kW (and not over 27 kW) is illustrated in the following two examples:

A. Ranges all the same rating (See Table 220.55, Note 1)

Assume 24 ranges each rated 16 kW. From Table 220.55, Column C the maximum demand for 24 ranges of 12 kW rating is 39 kW.

16 kW exeeeds 12 kW by 4

5% x 4 = 20% (5% increase for each kW in excess of 12)

39 kW x 20% = 7.8 kW increase

39 kW + 7.8 kW = 46.8 kW (value to be used in selection of feeders)

B. Ranges of unequal rating (See Table 220.55, Note 2)

Assume:

5 ranges each rated 11 kW

2 ranges each rated 12 kW

20 ranges each rated 13.5 kW

3 ranges each rated 18 kW

5 x 12

= 60 kW (Use 12 kW for range rated less than 12)

2 x 12

= 24 kW

20 x 13.5

= 270 kW

3 x 18

= 54 kW

30 ranges

408 kW total kW

408 kW ÷ 30 ranges = 13.6 kW (average to be used for calculation)

From Table 220.55, Column C, the demand for 30 ranges of 12 kW rating is 15 kW + (1 kW x 30 ranges) = 45 kW.

13.6 exceeds 12 by 1.6 (use 2 kW)

5% x 2 = 10% (5% increase for each kW in excess of 12 kW)

45 kW x 10% = 4.5 kW increase

45 kW + 4.5 kW = 49.5 kw: (value to be used in selection of feeders)

Article 90 Introduction

General

Wiring and Protection

Wiring Methods and Materials

Equipment for General Use

Special Occupancies

Special Equipment

Special Conditions

Tables

Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size

Annex D. Examples

Annex E. Types of Construction



Pocket Guide to the National Electrical Code 2005
Pocket Guide to the National Electrical Code(R), 2005 Edition (8th Edition)
ISBN: 0131480014
EAN: 2147483647
Year: 2004
Pages: 120

Flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net