Schedule of Test Results Explained

Circuit details

The left-hand columns describe the circuit before any test result appears. They identify the circuit, its function and the conductors: the cross-sectional area (csa) of the live conductors and of the circuit protective conductor, so the reader knows what was installed. Alongside that sit the protective device details — its type, its rating in amps and the BS number of the device.

These details are not filler. The Zs limit a circuit must meet, the sizing checks and the RCD expectations all depend on the type and rating of the protective device, so recording them accurately is what makes the rest of the row meaningful.

Continuity and ring-final values

Continuity confirms the conductors are unbroken and correctly connected. For most circuits this is recorded as R1+R2 — the combined resistance of the line and protective conductors — or as R2 alone where that method is used. A sound, low reading tells you the earth path is intact end to end.

Ring final circuits get extra columns because they need extra proof that the ring is genuinely a ring. The r1, rn and r2 end-to-end readings — line, neutral and protective conductor measured around the loop — are recorded so that a broken or interconnected ring shows up in the figures rather than hiding as a healthy-looking radial.

Insulation resistance, polarity and Zs

Insulation resistance is recorded (in megohms) to show the insulation between conductors, and between conductors and earth, is healthy and not leaking. A high value passes; a low one warns of breakdown. Polarity is confirmed and recorded to prove that line, neutral and earth are connected the right way round throughout — that switching and protection are in the line conductor, not the neutral.

The measured Zs column records the earth fault loop impedance actually measured at the circuit. It is checked against the maximum permitted for that protective device: if the measured Zs is within the limit, enough fault current will flow to disconnect the supply in the required time. This is one of the most important figures on the whole schedule.

RCD and functional tests

Where a circuit is RCD-protected, the schedule records how the device performed. The ×1 test applies the rated residual current and records the disconnection time; the ×5 test applies five times the rated current and records the (faster) disconnection time, confirming the RCD trips quickly under a larger fault. The integral test button is also operated to confirm the mechanical trip works.

Finally, functional tests confirm that switchgear, controls and the like operate as intended. Together with the electrical readings, the functional column completes the row — the whole point being that a fully filled-in row is a self-contained demonstration that the circuit is safe and compliant.

The columns at a glance

The table below lists the columns you would expect on a typical schedule of test results and what each one records.