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Hi guys. Ive generally no problem going through the deign process of cable selection for a circuit to be installed, (i try keep my hand in now and then rather than just looking in the OSG) but when i look at a RFC as in appendix 15, i get a little stuck. Ib = 32A, so In = 32A breaker, take it the cable is clipped direct to avoid any correction factors in this example, so far so good. So now i find a cable Iz, from the tables in appendix 4 to carry this 32A, im looking at table 4D5. Here, i feel sure we treat this ring as two radials supplying any particular SO on the ring. So each leg now needs to be able to carry 16A, and im assuming here, that we select 2.5mm T&E because of the time current characteristics of our 32A CB?, as both 1.0 and 1.5mm sq cable can carry this load, but could become a serious hazard under fault conditions, whereas 2.5 shouldn't?!
Also, do we calculate the voltage drop over the entire length of the cable, taking it that a SO could be midway or a few inches from the origin of the circuit? and the long leg would suffer far more volt drop?
Cheers
Also, do we calculate the voltage drop over the entire length of the cable, taking it that a SO could be midway or a few inches from the origin of the circuit? and the long leg would suffer far more volt drop?
Cheers