Adiabatic Equation for calculating the minimum cpc (circuit protective conductor) and earth minimum csa sizes of earthing conductors, S = √(I²t) / k.
This Adiabatic Equation Calculator takes into account the following parameters:
t = Disconnection time (seconds).
k = Conductor k value (From BS 7671 tables).
la = Fault current (PEFC in Amps).
I² = la x la.
Results with the minimum CSA mm².
Values of K are obtained from the tables within BS 7671:
- Table 54.2 : Conductor not incorporated in a cable and not bunched with cables.
- Table 54.3 : Conductor incorporated in a cable or bunched with cables.
- Table 54.4 : Sheath or armour of a cable.
- Table 54.5 : Steel conduit or trunking.
Disconnection times (t) are obtained from the maximum operating time/current characteristics tables within BS 7671:
- Fig 3A2 (a,b) : BS 3036 semi-enclosed fuse.
- Fig 3A3 : (a,b) : BS 88-2.2.
- Fig 3A4 : BS EN 60898 / 61009-1 MCB/RCBO type B.
- Fig 3A5 : BS EN 60898 / 61009-1 MCB/RCBO type C.
- Fig 3A6 : BS EN 60898 / 61009-1 MCB/RCBO type D.
- BS 1361 Fuse.
How to use the Adiabatic Equation App:
1) Input your voltage value.
2) Input your Zs value.
3) Select protective device.
4) Select protective device rating.
5) Select conductor type.
6) Select conductor material.
7) Tap calculate.
