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In the Whitfield guide to the 16th edition, Chapter 4, examples 4.1,4.2 & 4.3 (pages 57-60 in my edition) refer to cabling for an immersion heater.
In Ex4.1, the grouping-factor and Ci for a 50mm run in thermal insulation are taken combined, because the cablerun is subject to the two factors in the same location. Also, this value (0.463) is lower than that of the Ca (0.71). Therefore, only the Cg*Ci are used in the calculation.
In Ex4.3, the same cablerun is specified, but Ci does not appear in the calculation for rated current, and Ca does.
Yet still the Cg and Ci product is lower than the Ca.
what am I doing wrong?
In Ex4.1, the grouping-factor and Ci for a 50mm run in thermal insulation are taken combined, because the cablerun is subject to the two factors in the same location. Also, this value (0.463) is lower than that of the Ca (0.71). Therefore, only the Cg*Ci are used in the calculation.
In Ex4.3, the same cablerun is specified, but Ci does not appear in the calculation for rated current, and Ca does.
Yet still the Cg and Ci product is lower than the Ca.
what am I doing wrong?
