If I upgrade switch//fuse units to a consumer unit how

Aug 18, 2023

Question:

My current domestic supply was installed 40 years ago and has an Isolator/Fuse unit in the garage. The feed from the Isolator/Fuse unit is 16mm T&E round the walls of the attached garage to the bungalow which has two switch/fuse units, for power and lighting, which I wish to replace with a new Consumer Unit. The cable length to the switch/fuse units is approximately 22 metres. I understand that the cable needs to be upgraded to 25mm.Point 1. Is it satisfactory to add a 10mm T&E in parallel with existing 10mm cable, to meet the 25mm requirement for current tails size.Point 2. In fitting a SPD. device, should it be at the Isolator/Fuse unit in the garage, close to the incoming feed and earth, or can it be fitted at the Consumer unit. The very specific wire lengths associated with installing an SPD, especially as far as the Earth connection is concerned, is the main reason for the question.

Answer:

Hi there.

If you are looking to upgrade the installation, then seeking the advice of a local tradesman would be best as they can see the installation.

It is very difficult to parallel cables of different sizes, so this would be unwise.

An SPD could be installed at either point, the length of the cable is related to the connection to the earthing terminal.

I am sure a decent Part P registered ECA Member will be able to help.

Hope this helps.

Gary Parker - ECA

Gary holds a Bachelor of Engineering Degree in Electrical & Electronic Engineering along with numerous years of experience across many aspects of the electrical industry.