Basic cable calculation
Checking Iz
From BS7671
Method is used in items 5.1 and 5.2 Ib or In / Correction factors
Checking Iz
From BS7671
Method is used in items 5.1 and 5.2 Ib or In / Correction factors
It should be noted that the value of (It) appearing against the chosen cross-sectional area is not (Iz).
It is not necessary to know Iz where the size of conductor is chosen by this method.
But it is possible to get incorrect coordination with cable calculations that seem acceptable?
But it is possible to get incorrect coordination with cable calculations that seem acceptable?
Ib 28A
In 32A
L 40m
Ca 0.94
Cg 0.7
Cable T&E
Clipped direct
Calculation
It ≥ Ib ÷ correction factors so: It ≥ 28 ÷ 0.94 x 0.7 = 42.5A
Table 4D2A Method C 6mm2 cable - 46A It = 46
Volt drop 8.17V
So 6mm cabe looks OK
But if I do check Iz
Iz = It x Correction factors 46 x 0.94 x 0.7 = 30.26A
Ib ≤ In ≤ Iz 28 ≤ 32 ≤ 30.26
