Why should your electrician carry out tests?
Besides you wanting your new electrical installation to work so you can put the lights on, cook, shower and watch TV, there are some very important reasons why your electrician tests (or SHOULD test) and record the test results on a relevant test results form.
Correct Sizing and Installation of Conductors
On one hand electricians need to ensure that the cables, cable terminations, switches and other accessories, are correctly sized and installed. If too much current is drawn through a cable not designed to carry such a load, the cable could heat up and potentially melt. Likewise, if terminations have not been correctly made, this could lead to arcing and excessive heat being caused.
Both of these examples have the potential of causing fires, as can other poorly or incorrectly installed circuits and fittings.
The sequence of tests the electrician should carry out is designed to identify any such problems, so they can be either be rectified before the electrician leaves you, brought to your attention so any remedial work can be agreed on. In the more severe cases the electrician should isolated the problem so that it (or that part of the circuit) will remain inactive until the problem has been fixed.
Earth Fault Loop Impedance Testing
A different kind of problem could arise from a fault occurring due to things going wrong during the lifetime of an electrical installation. This could be, for example, someone putting up a shelf or picture on a wall and accidentally drilling or screwing into an electric cable which is buried in the wall. It could also be due to something going wrong with an appliance such as kettle, iron, toaster or washing machine, where something called an earth fault can occur.
If such a problem occurs, there is a risk of someone getting an electric shock or even being fatally electrocuted.
Testing of Protective Devices and Disconnection Times
Some of the tests that the electrician should carry out are designed to confirm that the circuits, including the earth part of each circuit, is capable of causing the protective devices in the consumer unit to operate quick enough to remove the danger before anyone, including pets, gets hurt.
In electricians terms this is called Automatic Disconnection of Supply (or ADS), and it is the electricians responsibility to carry out tests to ensure that this works within the limits set by the electrical wiring regulations.
Insulation Resistance Testing
Cable degradation due to age, exposure to the elements, damage, etc., can lead to short circuits, arcing or excessive heat being generated. Therefore the electrician should also conduct insulation resistance tests to ensure that there is sufficient insulation between the live and earth conductors (L-N, L-E and N-E) throughout the entire length of the circuit.
Confirmation that this has been done and the values taken should be recorded on the test sheet.
What if the Electrician does not test?
If your electrician has installed a new circuit, an Electrical Installation Certificate (EIC) MUST be issued, accompanied by a Schedule of Test Results. The results of the tests, some of which have been described above should be recorded on the Schedule of Test Results form.
If your electrician has added a spur to an existing circuit, added a lighting or switch point, or carried out other relatively small alterations which extend beyond the like for like replacement of sockets or switches, a Minor Electrical Installation Works Certificate (MEIWC) should be issued. The completion of the MEIWC should also include test results for many of the tests highlighted on this page, so please insist on a Minor Electrical Installation Works Certificate being issued based on the criteria I have described here.
You, as a paying customer, are entitled to the correct certification being issued, and your electrician is obliged to provide you with such, so please ask.