Comparison

Max Zs Values vs Grant TechBox

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head

Max Zs Values

Zs Values 18th Edition BS 7671

Access Grant manuals on the go

Free

🔍 Reference

No ratingsView app →

About

Max Zs Values

This app calculates and displays maximum permitted Zs values for electrical installations, adhering to the 18th Edition of BS 7671. It includes 80% temperature adjusted values and manufacturer charts for MCCB devices, along with a converter for older Zs values.

Highlights

100% BS 7671 Zs Values
80% On Site Guide Zs Values
Adjustable disconnection times (0.4s, 0.2s, 5s)
BS EN Device Zs calculation
MCCB 60947-2 Zs charts
Zs Converter for 18th edition

Features

Read full description

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.

About

Grant TechBox

Features

Read full description

Get access to Grant technical manuals anywhere, anytime with the Grant TechBox mobile support app for iPhone and iPad devices. Designed for heating engineers and installers, the TechBox makes finding installation manuals and technical resources quick and easy, whether you are online or offline. From Grant oil fired boilers, flues and accessories through to air source heat pumps and other renewable heating products, this comprehensive technical library has it all. Find current and historic manuals in a few simple taps of the screen. • Download the Grant product categories most relevant to you and your business • Find documents with ease via user-friendly navigation • Save favourites for documents you regularly use • Toggle between current and archive to access historic manuals • Use offline even when you have no WiFi or internet connection

Screenshots

Max Zs Values4 screens

Grant TechBox4 screens

Verdict

The call

The clearest difference is price: Grant TechBox at Free against Max Zs Values's $9.99. Max Zs Values's advantage is update cadence (every 4 months vs every 12 months) and iOS requirement (11.0 vs 15.0). On ads, in-app purchases and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Grant TechBox is free to download; Max Zs Values costs $9.99 up front. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

Max Zs Values ships an update every 4 months, Grant TechBox every 12 months. The most recent releases landed on September 24, 2026 and September 3, 2026 respectively.

Scorecard3 real differences · 5 level

Max Zs Values versus Grant TechBox: the parameters behind the verdict, then further details
Parameter	Max Zs Values	Grant TechBox
Price	$9.99	Free — better
Positive reviews	55.2% of reviews	—
Update frequency	Every 4 months — better	Every 12 months
Ads	No	No
In-app purchases	No	No
Monetization	Paid	—
Devices	iPhone, iPad, iPod	iPhone, iPad, iPod
Requires iOS	11.0 — better	15.0
Further details — not scored
Size	15 MB	47 MB
Age rating	4+	4+
Developer	Pro Certs Software Ltd	Grant Engineering UK LTD

In-app purchases

None

Max Zs Values

No in-app purchases

None

Grant TechBox

No in-app purchases

Questions

Is Max Zs Values free?

Max Zs Values costs $9.99, with no in-app purchases.

Is Grant TechBox free?

Grant TechBox is free to download, with no in-app purchases.

Do Max Zs Values or Grant TechBox have ads?

Neither Max Zs Values nor Grant TechBox shows ads.

Which is updated more often, Max Zs Values or Grant TechBox?

Max Zs Values ships an update every 4 months, and Grant TechBox every 12 months. Most recently, Max Zs Values was updated on September 24, 2026 and Grant TechBox on September 3, 2026.