This article relates to the electrical earthing requirements for homes. As all electrical work in homes must now be carried out by trained electricians this article is not designed to help you to amend the electrical earthing in your home and you must not attempt to perform this work.
Electrical Earthing Definition
Earthing is the term used to define the connection of “exposed conductive parts” of an installation or appliance to the main earthing terminal for that electrical installation.
The means of earthing of an electrical installation is the method of connection to the general mass of earth (the ground) for the exposed conductive parts. The exposed conductive parts are connected to the general mass of earth via the main earth terminal.
Prior to starting any electrical installation work the electrician you employ should visually inspect the electrical supply arrangements to establish that there is a provision of a satisfactory means of connection to the main earthing terminal.
What happens where no main earth is present or it is unsatisfactory?
Where it is found that electrical installation has no visible main connection to earth and /or the installations “Earth Loop Impedance” is unacceptably high, the installer /electrician should not connect any new work to your electrical system. If the Earth Loop Impedance is high there is not a free path for the electricity to safely flow to the ground.
Further investigations will then be required to establish where the earth path is within your house. It was the practice in the past to use the water pipes, this is no longer satisfactory and has not been permitted since 1966 as any work on your water supply would involve use of temporary earth bonds to bridge sections of water pipe where possible .
It has never been allowed to use a gas pipe as an earthing path.
Should I be advised?
As this is a significant safety risk the electrician should explain the situation to you advising that the electrical installation does not comply with the current standards and building regulations. In its present format the electrical installation could pose a potential danger if not rectified and must be corrected before the new installation can be connected. You should also be advised of the work is required to establish a safe electrical system for the whole house and not simply a requirement for the new appliance they were working on.
What would happen next?
If they are acting for you the electrician should contact the mains equipment supplier and request the earliest installation of a Protective Multiple Earthing system (PME) if available. They will also issue an “At Risk” notice to you detailing the nature of the problem.
The mains equipment supplier will carry out the work and submit any charge for the installation of the PME directly to you. Once the mains equipment supplier has installed the PME system, the electrician would be able to return to your property, carry out the appropriate tests, connect the installation and issue an appropriate Electrical Certificate.
What is a PME is unavailable in a short timescale
Where a PME is unavailable or the lead-time offered by the supplier for PME conversion is unacceptable to you the trained electrician may offer to install a permanent earth spike and RCD.
Should you refuse both options, any electrical installation will not proceed.