Trying to locate updated Zs tables for obsolete and/or older overcurrent protective devices such as MCCB’s or discontinued MCB’s is just about impossible to find as they very rarely exist.
With our new Zs Converter you can convert from old Zs values to the 18th edition 2018 230v Cmin Zs values.
Convert an old Zs value to an 18th edition 230v Cmin value
1 – Zt: Enter the old Zs value (of a previous version of BS 7671).
2 – V1: Enter the Uo voltage at which the old Zs value was tabulated at, i.e. 230v or 240v.
3 – Select a conversion option: “18th Edition 230v Cmin” or select “Custom Value (V2)” to enter a different target voltage value.
This Zs Converter app will convert any Zs value from a previous version of BS 7671 to the 18th edition Zs value, or a custom value based on any voltage.
Max Zs Conversion Example.
As an example, a BS EN 60898 Type B 32 Amp MCB maximum Zs value to BS 7671 16th edition was 1.44 Ω, to convert this to the 18th edition value;
- Zt = 1.44
- V1 = 230
- Select Convert to option: 18th Edition @230v Cmin value
- Result = 1.37 Ω
One of the unique features of the Zs Converter is you also can convert an 18th edition Zs value to a previous version BS 7671 Zs value, this can be useful to confirm if a specific measured Zs value complied at the time it was installed. Note: All measured Zs values must comply with the current edition of BS 7671.
Convert an 18th edition Zs value to a previous version of BS 7671
An example of this could be converting a 16th edition Zs value to an 18th edition Zs value. As a quick example, a BS EN 60898 Type B 32 Amp Zs value to BS 7671 16th edition was 1.44 (@240v).
1 – Zt: Enter the 18th edition Zs value.
2 – V1: Enter the Cmin Uo voltage value of “218.5”.
3 – V2 (Custom Value): Enter the previous version of BS 7671 Uo voltage value, such as 230v or 240v.
Disclaimer: Converted Zs values should be checked and verified with the manufacture of the device before implementing.