# Max Zs Values

> Zs Values 18th Edition BS 7671

Canonical page: [https://chrome-stats.com/d/id498838137](https://chrome-stats.com/d/id498838137)

## Overview

- **ID:** `id498838137`
- **Platform:** Apple
- **Type:** Apple app
- **Status:** Available
- **Publisher:** Pro Certs Software Ltd
- **Category:** Reference
- **Version:** 3.1.18
- **Last updated:** 2025-07-29
- **First published:** 2012-02-12
- **Size:** 15 MB
- **Data as of:** 2026-09-24
- **Store listing:** [Apple App Store](https://apps.apple.com/us/app/max-zs-values/id498838137)
- **Website:** [https://www.procertssoftware.com/max-zs-values/](https://www.procertssoftware.com/max-zs-values/)
- **Privacy policy:** [https://www.procertssoftware.com/privacy-policy](https://www.procertssoftware.com/privacy-policy)

## Description

A comprehensive database of maximum Zs values for fuses, MCB's, RCBO's, and RCD's. Also includes many manufacturer MCCB BS EN 60947-2 and ACB maximum Zs tables.

Calculate and look up the maximum permitted Zs value ( earth loop impedance ). Max Zs Values also includes the 80% temperature adjusted values and a some MCCB 60947-2 manufacture Zs charts.

- 100% BS 7671 Zs Values
- 80% On Site Guide Zs Values

- 0.4 (s) second disconnection times
- 0.2 (s) second disconnection times
- 5 (s) second disconnection times

- Common BS EN Devices:
Scroll through the list of protective devices and select the device rating to calculate the maximum permitted Zs value for your selected protective device and rating combination.

- 60947-2 MCCB's Zs Tables:
Look up the maximum permitted Zs tables for a selection of MCCB manufacture devices (some).

- Maximum Zs Features:
+ Maximum Disconnection Times
+ BS 7671 18th Edition Zs Tables
+ Fuse's
+ MCB's
+ RCBO's
+ RCD's in TT earthing systems
+ Max REC Ze values
+ 100% values
+ 80% values
+ 0.4 second disconnection times
+ 0.2 second disconnection times
+ 5 second disconnection times 
+ Uo 55v (U 110v) single phase and Uo 63.5v (three 
    phase) Zs values
+ BS EN 60947-2 MCCB manufacture device charts 
   (some)

There is now a new "Zs Converter" to convert old Zs values to the new 18th edition 230v Cmin Zs values.

Check out our collection of electrical apps such as the "Pro Certs" Electrical Certification App for iPad.

## Rankings

- #2,155,242 — Overall

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Source: [Chrome-Stats](https://chrome-stats.com/d/id498838137)