Frequently Asked Questions


1. What is main equipotential bonding?

A: Connections are made between the incoming GAS, WATER and OTHER services entering the property to the main earthing terminal. If the electrical system has a fault the main equipotential bonding will help to decrease the risk of receiving a dangerous electrical shock from indirect contact.

2. What is supplementary equipotential bonding?

A: This is required in rooms or locations which have an increased shock risk such as rooms containing a bath or shower. Metal parts are connected to the protective conductor of each circuit supplying Class I and II equipment in zones 1-3. This reduces any potential difference between any of these parts during an earth fault condition and reduces the risk of receiving a dangerous electrical shock.

Under the 17th Edition (1st July 2008) supplementary equipotential bonding can be omitted if all circuits to the room have RCD protection, main protective bonding is installed and circuits comply with the maximum disconnection times.

3. I want to have a new consumer unit fitted without having any other electrical work carried out is this possible?

There is no legal requirement or regulation in BS 7671:2008(2012) requiring you to upgrade your electrical installation to current standards.

However the electrical contractor should always check that the main earthing terminal is connected to an adequate means of earthing and that the main equipotential bonding is adequate - if either of these are unsatisfactory the contractor should refuse to install a new consumer unit unless you agree to any upgrading needed for these 2 items.

As from 1st July 2008 any/all works including replacement consumer units will have to comply with the new IEE Wiring Regulations BS7671:2008. Therefore

RCDs/RCBO's will have to be fitted to the consumer unit to protect socket-outlets, bathroom circuits and cables concealed in walls and partitions. See BS7671:2008

Don't forget - Part P applies to the installation of a new/replacement consumer unit.

The contractor will also check out other items of your electrical installation and if you do not want the work carried out then a risk assessment will be carried out. The contractor will issue an Electrical Installation Certificate for the work done and this will list any parts of your installation which do not comply with BS 7671:2008. You should also be notified in writing of any risks which exist in not upgrading your installation and the recommendation that your installation should have a full periodic inspection and test to check all circuits as soon as possible.


4. Do I need an RCD (residual current device) for my shower?

A: If a new circuit is required YES, because all new circuits to a room containing a bath or shower mus thave RCD protection.

If you are just replacing a shower and the manufacturer's installation instructions do not require RCD protection then No.

5. I have been told that I have to change from unswitched socket outlets to switched to comply with BS 7671- is this right?

A: Provided that your unswitched socket outlets meet BS 1363 then they comply with BS 7671 and you do not have to change them.

6. My installation has BS 3036 rewireable fuses and I have been told that the consumer unit must be replaced by one containing circuit-breakers - is that correct?

A: No, these fuses can still be used. The fuses should be checked to ensure that they are undamaged, that the correct size of fuse wire has been installed, that the associated circuit is adequately protected and that the required disconnection time is achieved.

7. I want some more sockets added do they have to be RCD protected?

A: If the final circuit includes power sockets is not already RCD protected, either the circuit will need to have RCD protection added, or the new socket outlets must incorporate RCD protection.



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