Electric-Light Fitting (Paperback)

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1914 edition. Excerpt: ...sizes of cables and their current-carrying capacities calculated at approximately 1,000 amperes per square inch sectional area of copper; at this density a voltage drop of 2.5 would occur for every 100 yards run of cable. From this table it will be found that a 7/16 cable carries 22 amperes, which is slightly more than the estimated maximum load; but the next size smaller is only intended for 17 amperes, so it will have to be 7/16 for the mains. Before deciding upon the size of the sub-mains feeding the two distribution boards we must consider upon what system they shall be run, i.e. whether " looped " or " independent," and the positions in which the boards shall be fixed. As there are only two boards and no likelihood of independent control being required, the partially "looped"; iii First Floor Distribution Boad Sub. Mains To First Floor system will be the right one to adopt. As regards positions, they should be fixed as central as possible, and in inconspicuous but at the same time accessible places. These positions should then be marked on the plans as shown. If the installation had been in a large hospital, factory or public building, necessitating a number of distribution boards widely scattered, and probably requiring separate control, then the "independent" system would be the best to use, each distribution board being supplied from a main distribution board, having D.P. switches and fuse, or as is sometimes used D.P. fuses and S.P. switches. Fig. 205 shows the arrangement of mains and sub-mains it is Mains Position For' Transformer If Used Fig. 205.--Arrangement Of Main Switch And Fuses, DistribuTion Boards, Mains And Sub-mains. proposed to install. The dotted square indicates where a...