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Field Testing & Twin SaaS
🇬🇧 Full UI + PDF + National Standard Mapping: UI + PDF in English. Normative references follow international IEC 60364, BS 7671:2018+A2:2022, IEEE, and NFPA 70E/70B.
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#02Loop Impedance (Zs) & Breaker Validation Calculator

Project Framework (report reference): IEC 60364-4-41Applicable Standard: IEC 60364-4-41 / BS 7671
Module Field Guides, Standard Selection & Tutorials (3)Browse All 93+ Guides →
1 · Field Measurement ProcedureHow to Measure & Test Loop Impedance Zs on Site: Step-by-Step Field Procedure (IEC 60364-4-41 / BS 7671)2 · Standards & Limit TablesWhich Standard Applies to Loop Impedance Zs? Acceptance Limits, Annex Tables & Regional Equivalents (IEC 60364-4-41 / BS 7671)3 · OhmCert Tutorial & Case StudyHow to Complete a Loop Impedance Zs Certificate in OhmCert: Worked Case Study & Troubleshooting

Multi-Asset / Multi-Point Equipment Schedule

Inspect multiple transformers, panels, rooms, motors, or RCDs in this module without overwriting previous assets. Each item receives a permanent QR Sticker UID preserved across annual audits.

Sticker UID: OC-LOOP-5B69
Plant & SLD (Auto-SLD)

Standard Limits, Equations & Space Presets

IEC 60364-4-41 / BS 7671 Maximum Loop Impedance Zs tables for MCBs (Type B/C/D) and fuses, Cmin = 0.95 voltage factor, 0.8x ambient temperature correction, and IEC 60364-5-54 adiabatic PE conductor k factors.

One-Click Normative Presets (Auto-fills Target Limits)

Measured Inputs

Uo is synced from project settings (230 V).

Calculated / Evaluated Results

Parametric engine: Zs_limit = (0.95 x Uo) / Im with Cmin = 0.95 (IEC 60364-4-41 / BS 7671), Zs_max_site = 0.8 x Zs_limit for 20 degC ambient testing. Also verifies TT/TN RCD touch voltage (Zs x I_dn <= 50 V) and IEC 60364-5-54 Clause 543.1.2 adiabatic PE conductor thermal withstand S_min = (Ik_min x sqrt(t)) / k.

  • Prospective Earth Fault Current Ik_min = (0.95 x Uo) / Zs

    - A

    Evaluated for TN-S arrangement at Uo = 230 V.

    Pending

  • Breaker Magnetic Trip Ratio (Im / In)

    -

    Not tested - enter the measured value. Acceptance: Im >= In (EN 60898-1: Type B = 5x In, Type C = 10x In, Type D = 20x In) [EN 60898-1 / IEC 60947-2]

    Pending

  • Overcurrent Magnetic Disconnection (Ik_min >= Im)

    -

    Enter measured Zs and magnetic trip setting Im to evaluate overcurrent disconnection.

    Pending

  • Calculated Base Limit Zs_limit = (0.95 x Uo) / Im

    - Ohm

    Maximum loop impedance at conductor maximum operating temperature.

    Pending

  • Max Allowable On-Site Limit Zs_max_site (0.8x Temp Corrected)

    - Ohm

    Zs_max_site = 0.8 x Zs_limit per IEC 60364-6 / BS 7671 Appendix 3 (20 degC ambient test).

    Pending

  • RCD Touch Voltage & Loop Coordination (No RCD selected)

    -

    Select an RCD rating IΔn and enter Zs to verify Zs x IΔn <= 50 V (IEC 60364-4-41 §411.5.3).

    Pending

  • Adiabatic Minimum PE Size S_min = (Ik_min x sqrt(0.4 s)) / 115

    - mm2

    IEC 60364-5-54 Clause 543.1.2 adiabatic thermal withstand requirement.

    Pending

  • PE Conductor Thermal Withstand Verification (S_PE >= S_min)

    -

    Enter Measured Zs and PE Conductor Cross-Section S_PE (mm2) to verify thermal withstand.

    Pending

Verification Checklist (0 / 12)

Pending

  • 1Supply earthing arrangement (TN-S / TN-C-S / TT / IT) and external Ze confirmed at origin [IEC 60364-6 §643.7]

  • 2Protective conductor continuity (R1 + R2) verified end-to-end before live Zs testing

  • 3Polarity verified at distribution board and furthest socket/load point

  • 4No-trip / high-current loop test mode selected appropriately for circuits protected by RCDs

  • 5Measured Zs <= 0.80 x Zs_limit (20 degC ambient correction) or verified against adiabatic heating

  • 6Prospective short-circuit / fault current Ipf <= rated breaking capacity Icn / Icu of protective device

  • 7RCD trip time verified at 1x IΔn (<= 300 ms) and 5x IΔn (<= 40 ms for 30 mA additional protection)

  • 8Protective conductor cross-section S_PE satisfies IEC 60364-5-54 adiabatic equation S_min = Ik·sqrt(t)/k

  • 9No downstream Neutral-to-PE bridge (illegal N-PE bond) present after main equipotential point

  • 10Adjustable MCCB / ACB electronic trip unit dials (Ir, tr, Isd, tsd, Ii, Ig) verified against selectivity study

  • 11Terminations torque-checked and distribution board circuit schedule updated

  • 12MFT loop tester lead nulling and ISO/IEC 17025 calibration validity verified

General Notes

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Free plan: 5 of 5 inspections / calculations left this month.