Electrical Testing Calculator UK - EICR & Installation Testing Tools

BS 7671 Testing Requirements

All electrical installations must be tested before being put into service, and periodically thereafter. These calculators help verify compliance during inspection and testing.

Initial Verification (New Installations)

Required tests per BS 7671 Part 6 (Chapter 61-64):

1. Continuity: Protective conductors and bonding
2. Insulation Resistance: Between conductors and earth
3. Polarity: Correct connections throughout
4. Earth Fault Loop Impedance (Zs): Verify automatic disconnection
5. RCD Testing: Trip times and residual current
6. Functional Testing: All equipment operates correctly

Periodic Inspection (EICR)

Recommended inspection intervals per IET Guidance Note 3:

• Domestic (Rental): 5 years
• Domestic (Owner-Occupied): 10 years
• Commercial/Industrial: 3-5 years
• Public Buildings: 1-5 years (risk-based)
• Temporary Installations: Before each use

More frequent inspections required after alterations, damage, or change of use

Recommended Test Sequence

Continuity of Protective Conductors

Test with installation de-energized. For ring circuits, use Ring Final Calculator to verify R1+R2 values.

Expected: Main bonding ≤0.05Ω, Ring final R1+R2 typically 0.3-1.0Ω for 2.5mm²/1.5mm²

Insulation Resistance

Test at 500V DC between conductors and between each conductor and earth.

Minimum: ≥1MΩ for SELV/PELV, ≥1MΩ for installations up to 500V (BS 7671 Table 61)

Polarity Check

Verify switches and protective devices are in line conductor, sockets wired correctly.

Use continuity tester or low-resistance ohmmeter

Earth Fault Loop Impedance (Zs)

Measure Zs at each point. Use Max Zs Calculator to verify measured values are within limits.

Measured Zs must be ≤0.8 × maximum Zs from Table 41.3 (temperature correction)

Prospective Fault Current (PFC)

Measure PSCC and PEFC at origin. Use PFC Calculator to verify protective device breaking capacity is adequate.

Protective device breaking capacity must exceed measured PFC

RCD Testing

Test trip time at ×1, ×5, and ×0.5 rated residual current. Test non-trip at ×0.5.

30mA RCD: ≤300ms @ 150mA (×5), ≤40ms @ 30mA (×1), must not trip @ 15mA (×0.5)

Required Test Instruments

Multifunction Tester (MFT)

Combined instrument for most tests - essential for EICR and installation certificates

• Continuity (low resistance ohmmeter)

• Insulation resistance (up to 1000V)

• Earth fault loop impedance (Zs)

• Prospective fault current (PFC)

• RCD testing (all parameters)

Additional Test Equipment

Supplementary instruments for specific tests

• Proving unit (voltage indicator verification)

• Socket tester (polarity and earth checks)

• Clamp meter (current measurement)

• Voltage tester (two-pole type)

• IR thermometer (temperature surveys)

Important: All test instruments must be calibrated annually and checked before each use. Prove voltage indicators dead before and after each test. Follow IET Guidance Note 3 procedures.