4.3
33 reviews
1K+
Downloads
Content rating
Everyone
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image
Screenshot image

About this app

Max Zs values for Android devices, look up the maximum permitted Zs values ( earth loop impedance ) as per BS 7671 18th edition. Max Zs values include 100% (BS 7671) and 80% (On site guide) temperature adjusted values.

Select from the list of protective devices (fuse's, MCB's, RCBO's) and device ratings to calculate the maximum permitted Zs value for your selected protective device.

Also look up some manufacture BS EN 60947-2 Zs value PDF charts and tables, all printable from within the Max Zs values app.

This Maximum Zs Values app contains Zs tables, charts and calculators all relating to the maximum permitted Zs values of BS 7671.

Max Zs Values Features:
+ BS 7671 18th edition Zs values
+ Common BS EN MCB's, RCBO's and fuses maximum Zs calculator
+ BS EN 60947-2 MCCB manufacture device charts / tables (some)
+ RCD max Zs for TT earthing systems calculator
+ REC max Ze (by enquiry) values
+ Uo 55v and 63.5v Zs values (110v single & three phase) calculator
+ Ze + R1+R2 = Zs calculator
+ Zs - Ze = R1+R2 calculator
+ TN & TT maximum disconnection times chart


A great electrical app to have at hand when you most need it for checking or calculating the maximum permitted Zs ( earth loop Impedance) values.

Max Zs Values is designed for Android tablets and phones. Don't forget to check out our other great collection of electrical apps for Android.

Our other electrical apps include "Pro Certs" (Electrical testing & certification app), "Cable Calc" (Cable size calculator) and many more visit https://www.procertssoftware.com/apps for more info.
Updated on
Feb 8, 2024

Data safety

Safety starts with understanding how developers collect and share your data. Data privacy and security practices may vary based on your use, region, and age. The developer provided this information and may update it over time.
No data shared with third parties
Learn more about how developers declare sharing
No data collected
Learn more about how developers declare collection

Ratings and reviews

4.3
33 reviews
Richard Lang
September 8, 2020
It's helpful app, but there is missing Zs values for disconnection times 1s in TT, No disconnection times for RCD's as per appendix 3, and few mistakes in wording in last section Maximum Disconnection Times like 411.3.2.5 see section 416 instead 419 and last 2 notes doesn't apply to 411.3.2.5 but 411.3.2.2. There should be explanation of symbols meaning like U0, Im, ir, Io. Have not clue what REC means. Developer means DO - Zs Values. I would expect little bit more from this app.
5 people found this review helpful
Did you find this helpful?
Pro Certs Software Ltd
September 23, 2020
Hi Richard, we have taken your comments on board and have updated the Max Zs Values (3.1.5) app to suit, thank you for your feedback. Re your comment on "disconnection times for RCD's as per appendix 3" this is not related to max Zs values, you can find RCD disconnection times tables in our Electrical Tools & Reference App.
johnny walsh
March 17, 2021
Using a Samsung a71. Good app, shame that the app display does not align properly on the screen Post Update. Credit to the Pro Cert team. They investigated the problem and fixed it. Many thanks 5 stars
4 people found this review helpful
Did you find this helpful?
Pro Certs Software Ltd
February 25, 2021
Hi, can you please send us a screenshot to support@pro-certs.com and we’ll look into fixing it.
james shirlaw
August 9, 2022
Looks like it could be a great app to have in the tool box but was looking for mccb maximum zs values from the manufacturer wylex but nothing . Hope it can be updated
Did you find this helpful?
Pro Certs Software Ltd
August 11, 2022
Hi, we have added a Wylex MCCB NHG range Zs table and a new "Zs Converter" tool to convert old BS 7671 Zs values to BS 7671 18th edition 230v Cmin values in version 3.1.11. - This update should be live in the store within a few hours.

What's new

08/02/2024:
- Added Schneider TeSys MCCB max Zs table.
- New PDF viewer to fix the pinch/zoom/scroll bug when viewing PDF tables.
- A few UI improvements.