Adiabatic Equation Calculator

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.