The schedule of circuit detailsWhere does circuit one start?

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The other side of the certificate. Almost all of it is read straight off the board in front of you.

How circuits are numbered

1→Number your circuits from the main switch outwards, not from the far end of the board back.

So on a typical board: the SPD sits next to the main switch and becomes circuit 1, then the first breaker is circuit 2, and so on. An RCD in the row isn't a circuit — you can write "RCD" in if you want, but there are no circuit details to record for it.

✋The SPD gets N/A all the way across. It isn't connected to a circuit, so there's nothing to test on it — it has its own check. A blank way gets "spare".

✋Don't draw lines through boxes. Write N/A, or run one horizontal line all the way across a row you aren't using. Never put a line through part of a row where you've filled information in elsewhere.

What goes in each column

Column	Where it comes from
Protective device BS EN	Read off the device
Breaking capacity	Usually printed on the side or the front — e.g. 6 kA. The unit is already on the form, so write the number only
Maximum Z_s	The Chapter 41 table figure: BS 7671 Table 41.3 for circuit breakers. A 32 A type B is 1.37 Ω. If you take the figure from another source, such as the OSG Table B6 80 % values, say so in the Remarks column (column 31)
RCD BS EN	For an RCBO it's the same number as the protective device. For a separate breaker and RCD: 60898 and 61008-1
RCD type and rating	Read the pictogram on the device. 30 mA, and the rating in amps matches the device — 32 A

Checking the SPD. Look at the window. Green means it's still in operation — tick it. Red means it has operated and needs replacing.

The polarity column — not the live one

✋There is a polarity column on the schedule of test results, and it is not the live supply polarity test. It's a tick box, confirmed during continuity. Circuit polarity is proved dead. What it confirms (Guidance Note 3, 2.6.12, p.77): every fuse and single-pole control or protective device is in the line conductor, and the centre contact of a screw lampholder goes to line (E14 and E27 lampholders to BS EN 60238 excepted).

It's partly a visual inspection — on an open accessory you can see which conductor went where. And it's partly proved by the test itself: a continuity reading between line and CPC reads open if a neutral has landed in the line terminal. A line and CPC swapped with each other still reads on that test — on a ring, step 2 finds it; otherwise it's what the visual inspection is for.

⚠A line-to-neutral reading alone does not prove polarity. Swap them over and you'd still get a reading, because all you've made is a loop. It's when the CPC is involved that the test shows a neutral sitting in the line terminal.

BS 7671 · Table 41.3 · max Z_s · 32 A type B = 1.37 Ω ★ OSG · Table B6 · the 80 % values · if used, say so in Remarks BS EN 60898 · 61008-1 · 61009

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18th Edition
Building Regs
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