The schedule is where a certificate or condition report proves each circuit. On the BS 7671 model forms from A2:2022 onwards it comes as two sheets: a schedule of circuit details (columns 1 to 16) and a schedule of test results (columns 17 to 31). The A4:2026 forms keep that layout, and blank copies are free from the IET. The IET notes that scheme and trade association forms can differ from the models, as long as they meet the minimum requirements of Appendix 6.
The board details at the top
- The board's reference, where it is, what supplies it, and the protective device on that supply.
- The type of any surge protective device (T1, T2 or T3) and whether its indicator shows it is working. Not every SPD has a visible indicator.
- Earth fault loop impedance at the board (Zdb) and prospective fault current (Ipf).
- Confirmation of correct polarity, and of phase sequence where it applies.
- Serial or asset numbers for each instrument you used, plus the tester's name, signature and date.
Circuit details: columns 1 to 16
| Column | What goes in |
|---|---|
| 1–2 | Circuit number, and a description the next person can match to the board. |
| 3 | Type of wiring, as the letter code from the key on the form, from A (thermoplastic insulated and sheathed cable) to H (mineral insulated), or O for anything else. |
| 4 | Reference method, taken from Table 4A2 in Appendix 4 of BS 7671. |
| 5 | Number of points the circuit serves. |
| 6–7 | Live and cpc conductor sizes in mm². |
| 8–11 | The overcurrent device: its BS EN number, type, rating in amps and breaking capacity in kA. |
| 12 | Maximum permitted Zs. By default this is the tabulated value from Chapter 41. If you use another source, such as manufacturer's data, name it in Remarks. |
| 13–16 | The RCD: BS EN number, type (AC, A, F or B), rated residual operating current (IΔn) in mA, and rating in amps. |
Test results: columns 17 to 31
Ring final circuit continuity (18 to 20)
Record the end-to-end resistance of the line (r1), neutral (rn) and cpc (r2). Line and neutral are the same size and length, so their readings should match closely, and so should the cpc if it is the same size. With 2.5/1.5 mm² cable, r2 should be about 1.67 times r1.
Then carry out the cross-connected tests at each socket. In the final step the line and cpc are cross-connected, usually at the board, and you measure between line and cpc at every point. Each reading is the R1+R2 to that socket. On a 2.5/1.5 mm² ring they stay substantially the same all the way round, close to (r1 + r2) ÷ 4. Column 27 needs the highest Zs, so use the highest reading when you add R1+R2 to Ze.
Rings in 4.0/1.5 mm² cable behave differently. IET analysis shows the line-to-cpc readings rise towards the middle of the ring and fall back towards the board, with the highest reading, at the mid-point, matching (r1 + r2) ÷ 4. If the earlier steps look right, don't read that pattern as a fault. Radial circuits don't use these columns.
Continuity (21 and 22)
Enter R1+R2 or R2, whichever you measured. Don't work out R1+R2 by taking Ze away from a measured Zs: the IET points out that parallel paths usually make measured Zs lower.
Insulation resistance (23 to 25)
Record the test voltage, then the live–live and live–earth readings in MΩ. For circuits up to 500 V, other than SELV and PELV, the test voltage is 500 V DC and the minimum is 1 MΩ, from Table 64. When the schedule goes with an EIC, test at the Table 64 voltage.
Disconnect surge protective devices and anything else likely to affect the reading or be damaged, and list vulnerable equipment in Remarks. For vulnerable equipment on an EICR, the IET's advice is to test only between the live conductors joined together and earth. A reading below 1 MΩ to earth is a C2 in Best Practice Guide 4.
Polarity (26)
Tick when polarity is correct. A schedule that goes with an EIC can't show incorrect polarity, so put it right before you certify.
Maximum measured Zs (27)
This is the highest earth fault loop impedance on the circuit. BS 7671 lets you measure it or determine it another way, and Ze plus the circuit's R1+R2 is a common calculation. The IET notes it cuts down live testing.
Allow for temperature before comparing with column 12. The Chapter 41 maximums assume conductors at their operating temperature, commonly 70 °C, and circuits are rarely that hot when tested. Appendix 3 of BS 7671 simplifies the correction with a factor of 0.8, and the tables in the IET On-Site Guide and Guidance Note 3 already include it. For readings close to the limit, you can do a more detailed calculation.
RCD (28 and 29)
Record the disconnection time in milliseconds from an alternating current test at the RCD's rated residual operating current (IΔn), whatever type the RCD is. A general non-delay RCD should operate within 300 ms, and an S-type time-delayed RCD between 130 ms and 500 ms. Since A2:2022 a test at five times IΔn hasn't been required, though extra tests are still allowed. Tick column 29 when the test button works.
AFDD and Remarks (30 and 31)
Tick column 30 when the AFDD's manual test button works. Not every AFDD has one. Use Remarks for equipment vulnerable to testing, the source of any maximum Zs not taken from Chapter 41, and details of any Type 3 SPD protecting sensitive equipment.
Common mistakes to avoid
- Measuring Zs live on every circuit at initial verification when calculation would do. The IET calls earth fault loop impedance the live test most often carried out unnecessarily.
- Comparing a cold Zs reading with an uncorrected Chapter 41 maximum, which can pass a circuit that doesn't comply.
- Working out R1+R2 as Zs minus Ze.
- Insulation testing with SPDs or electronic equipment still connected.
- Testing an RCD with loads still connected downstream. The IET says electronic equipment and long circuits can affect the result, and that many RCD testing problems turn out to be user error.
- Reading the uneven line-to-cpc results on a 4.0/1.5 mm² ring as a cross-connection or loose cpc.
- Recording FI for a low insulation reading instead of coding it. See our guide to EICR observation codes.