Is TestFast fully compliant with BS 7671:2018+A3:2024?

Yes, TestFast is fully compliant with BS 7671:2018+A3:2024 standards. Our EICR certificates are automatically generated to meet all current UK electrical safety regulations.

Can I use TestFast on my tablet or mobile device?

Yes, TestFast works on desktop, tablet, and mobile browsers. No app installation is required - simply access it through your web browser with full functionality across all devices.

How does NoteScribe™ OCR work?

NoteScribe™ OCR scans consumer unit labels and circuit descriptions — typed, handwritten, or faded — and builds your digital schedule instantly, eliminating manual data entry before you've even started testing.

Does TestFast work offline?

Yes, TestFast features a zero-lag workflow that works both online and offline, ensuring you can maintain your inspection flow regardless of internet connectivity.

How accurate are NoteScribe™ OCR and the Observation Builder?

Both run at around 95% accuracy in real-world use. NoteScribe™ OCR accuracy depends on picture quality — a clear, well-lit photo gets close to perfect results. The Observation Builder accuracy depends on input specificity — detailed notes produce perfectly coded observations every time. Either way, you review the result rather than type from scratch.

Do I need to be with a scheme to use TestFast?

Yes. You need to be registered with a recognised Competent Person Scheme to generate valid certificates. TestFast is built for qualified UK electricians only. Working in Scotland? Part P does not apply — get in touch after signup and we will sort your verification quickly.

How does TestFast work for teams and QS approval?

Add your team, assign jobs, and set roles — Electrician or QS. Each sparky works their report on site while you monitor progress in real time. The key feature: you are reviewing while they are still on site. Spot an error and they fix it in two minutes, not tomorrow.

What certificates does TestFast support?

TestFast currently supports EICR (Electrical Installation Condition Report), EIC (Electrical Installation Certificate), Minor Works Certificate, and Domestic Smoke Detection Certificate. Emergency Lighting certificates — installation and annual duration test — are coming soon. All certificates are built to current British Standards.

Max Zs for 40A Type 3 (BS 3871)

Maximum earth fault loop impedance per BS 7671:2018+A4:2026

BS 7671:2018+A4:2026

BS 3871 Type 3 MCB

40A rated current — Formula: 230×0.95/(multiplier×In)

Maximum Zs (80% for ambient testing)

Recommended for Testing

0.44Ω

Use this value when testing at ambient temperature (per Appendix 14)

100% BS 7671 Table Value0.55Ω

Raw Table Value

Standard

BS 3871

Type

Type 3

Rating

40A

All Type 3 (BS 3871) Max Zs Values

Quick reference for all available ratings (80% values)

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Understanding Max Zs for 40A Type 3 (BS 3871)

The maximum earth fault loop impedance (Zs) of 0.44Ω for a 40A BS 3871 Type 3 MCB ensures automatic disconnection of supply within the required time under fault conditions as specified in BS 7671:2018+A4:2026.

Why 80% Values?

When testing at ambient temperature, conductor resistance is lower than at operating temperature. BS 7671 Appendix 14 recommends using 80% of tabulated values.

Testing Requirements

• Final circuits ≤63A: disconnect within 0.4s
• Distribution/fixed equipment: 5s allowed
• Measured Zs must be ≤ 0.44Ω

EICR Testing Note

During an EICR, if measured Zs exceeds the maximum permitted value, record as Code C2 or C3 depending on the degree of non-compliance.

Frequently Asked Questions

What is the maximum Zs for a 40A Type 3 (BS 3871)?

The maximum earth fault loop impedance (Zs) for a 40A BS 3871 Type 3 MCB is 0.44Ω when testing at ambient temperature. This is 80% of the BS 7671 table value of 0.55Ω, as recommended by Appendix 14 for testing purposes.

Why use 80% of the BS 7671 Zs value?

BS 7671 Appendix 14 recommends using 80% of tabulated Zs values when testing at ambient temperature. This accounts for increased conductor resistance at normal operating temperature. The correction factor ensures your measured values will still comply when the circuit is under load and conductors are at their maximum operating temperature.

What if measured Zs exceeds 0.44Ω?

If the measured Zs exceeds 0.44Ω for a 40A Type 3 (BS 3871), the protective device may not disconnect within the required time (0.4s for final circuits up to 63A, 5s for distribution circuits). This should be recorded as Code C2 (potentially dangerous) or C3 (improvement recommended) on an EICR, depending on the severity and risk assessment.

Which BS 7671 table is this value from?

The Max Zs value for 40A BS 3871 Type 3 MCB comes from Formula: 230×0.95/(multiplier×In). This table provides maximum earth fault loop impedance values to ensure automatic disconnection within the required time for the BS 3871 standard.