Straight to the second fix

02Second fix

Accessories on, and nothing switched on

Second fix is the stage a client actually sees, which is exactly why it is the stage most often rushed. It begins after the plaster has dried and the decorator has finished, and it ends with a complete installation that has still never had a volt through it.

Terminations

A termination is either tight or it is a heater. Conductors are cut back to clean copper, stripped to the length the terminal wants rather than to whatever the strippers were set to, and seated so that no insulation is caught under the screw and no bare conductor stands outside the terminal. The circuit protective conductor gets sleeved where it needs to be, and conductors are identified so the next person opening that accessory is reading rather than guessing.

Screws are tightened to the figure printed in the accessory manufacturer's own instructions. That figure exists because terminal brass has a yield point: a connection done to feel is either loose enough to arc under load or crushed enough to break a strand, and both faults look identical from the front. A torque screwdriver is cheap and the instruction leaflet is free.

Section through a flush accessory, box and finished wall A cut view from the side. The masonry is hatched on the left, the plaster is a thin layer on top of it, the back box sits in a recess with its front edge level with the finished plaster, and the accessory face sits flat against the plaster with the conductor entering the box through a grommet. finished line face sits flat masonry
The box edge was set at first fix. If it was set to the blockwork instead of the finished plaster, this is the stage where that shows.

Faces, and the order of the trades

Accessories go on after decoration, because a face fitted first gets painted, and a painted face is either a cut line somebody has to live with or a replacement nobody budgeted for. Faces are pulled up square and flush: the box edge was set at first fix, so a face that sits proud or sunk is a first-fix question showing up two stages late, and it is corrected rather than tightened over.

Data and telecoms outlets are punched down at this stage, the patch positions at the other end are labelled to match, and the pairs are kept in their twist as far as the punch-down as the specification requires. On a small installation that is a short job; done badly it is the fault that appears six months later as an intermittent connection and is blamed on the hardware.

The consumer unit, and why it stays off

The unit is populated at second fix. Circuits are landed on their protective devices, the main switch and any residual current devices are fitted, and the way each circuit is identified at the unit matches the identification that went on the cable at first fix. What does not happen is energising to see whether it works.

A circuit that had a screwdriver in it an hour ago has not been tested. Switching it on first proves only that nothing failed in the first second, and it throws away the dead tests — insulation resistance in particular, which cannot be done once the installation is live and is the test most likely to find the nail somebody put through a cable while hanging a rail. The sequence costs an hour at the end of a job and is the reason the rest of the job is defensible.

Next stage: energising, testing and handover.