Wednesday 7th January 2009

I only want a small electrical job done

Yes it sounds easy doesn't it, but before any electrical work can be carried out there are a number of items that need to be checked.

The Earthing Arrangement of the supply

There are a number of earthing systems in the UK, the three most common being, TT, TN-S & TN-C-S (PME). The TN-S and TN-C-S system are provided by the electricity supplier. Once we have confirmed which system it is that you have, we can then move onto the main bonding.

Note:
If you do not have an earth provided by your electricity supplier, you will need to contact them and inform them that you wish to have them provide you with a means of earthing. I can only say at this point good luck, once you have started on this task you will see what I mean.

Main Bonding

It is a requirement of the wiring regulations (BS7671) that any extraneous metal work be connected to the Main Earth Terminal (MET), the most common are:

The size and condition of these must be checked, before any work can be carried out.

Supplementary Bonding

If the work is to be carried out in a bathroom, or a room containing a shower, it will be necessary to confirm that the supplementary bonding is present.

Additional Load

Any additional item of electrical equipment will add to the existing load on the circuit / system that it is connected to. Therefore there is a need to check that the circuit and system can accommodate the additional load without an adverse affect.

Existing Equipment

As with the additional load, any existing equipment such as switches, dimmers, fuse board, and cables must be capable of supplying/controlling the new addition.

Type of Protection for the Additional Item

Before we can connect a socket, light, or other electrical item to your existing installation, we must make sure that the type of protection is of the correct type and rating. It maybe that the item is a socket that could be used to supply a lawn mower, or hand held electrical tool that is to be used outside, if so then it must be protected by a 30ma RCD. Or it maybe the flood light that you have just brought from the DIY store, is a 500watts light and the circuit that you wish to put it on is already supplying 1000watts and has a maximum rating of 1200watts.

Cable Capacity and Volt Drop

Just as with the type of protection, we need to check that the cable is able to take the additional load and that the volt drop is within its limits. It could be that the circuit has a 20amp fuse and the cable is only capable of carrying 16amps.

Heating System

Before we can provide an electrical supply to a heating system, we must confirm that the bonding to the system is in place, and that any pipe work / radiator or tower rail that is in a bathroom or shower room has the necessary supplementary bonding.

Now the Good News

Should we discover that any of the above items that will be involved with the work you wish us to carry out, are not correct, we would not be able to proceed until it is put right.

Easy isn't it!!!!!!

Nine times out of ten, we find that all is okay and we can continue with the work for you, but we do need to check before we can carry it out.