Adiabatic Equation CalculatorThe Adiabatic Equation.
✔ Calculate Protective Conductor Size mm²
✔ Calculates la
✔ Calculates I²
✔ Calculates k value
✔ Calculates t (s)
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The Adiabatic Equation Calculator in an app. Calculate the minimum permissible cpc or earth size using the Adiabatic Equation.
Sizing of protective conductors can be achieved by looking up the relevant table or where required by calculation using the Adiabatic Equation.
Adiabatic Equation Symbols
- S = Protective Conductor Size (mm²)
- Ia = Fault Current (A)
- I² = la Squared
- t = Time (s)
- k = Conductor k Value
Conductor k Value Tables
BS 7671 Values of k for Protective Conductors:
- 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.
Adiabatic Equation Parameters
- Uo Voltage
- Measured Zs Value
- Protective Device Type & Rating
- Conductor Type
- Conductor Material
Disconnection Time Tables
BS 7671 Maximum Operating Time / Current Characteristics Tables:
- 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
A great app for electricians and inspectors carrying out electrical testing & inspecting for verifying existing protective conductor sizes.
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All your applications are very useful, quick to operate.
Awesome app so easy to use with correct results..
Saves messing with the maths,
very handy of your Z’s are low.
Adiabatic Equation Calculator
Seem to work spot on,
comes up with the same answer as i calculate on paper.
Minimum csa of cpc
The minimum csa of a cpc can be selected from the appropriate table in BS 7671. In certain circumstances the cpc csa can be calculated using the adiabatic equation for a specific circuit, this will determine the actual minimum csa of a cpc required for the specific circuit in question.
Earthing Cable Size Calculation
The calculation to calculate an earthing cable size (circuit protective conductor size) is the Adiabatic Equation. Earthing cable size selection charts can also be found in BS7671.
What is the Adiabatic Equation?
The Adiabatic Equation is the mathematical equation / formula used to calculate the minimum cpc size, if a non standard cable size is calculated then the next available larger size shall be used.
The preferred method for selecting a circuit protective conductor size is by selecting from the appropriate table in BS 7671.
The Adiabatic Equation might be used to calculate the absolute minimum size of a cpc for an existing installed cpc should that be smaller than that required of the appropriate table.
Adiabatic Equation Example
Here we demonstrate an adiabatic equation example, we will explain how the adiabatic equation calculator works.