Adiabatic Equation Calculator

The Adiabatic Equation calculator for calculating the minimum earthing and circuit protective conductor earth csa sizes in mm².

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.