A consumer unit should be installed by a qualified competent person in accordance with all relevant legislation and regulations including building regulations and wiring regulations BS7671. If in doubt contact a qualified competent person.
Until recently Split Load consumer units were probably the safest type of consumer unit available. As well as having overload and short circuit protection they also have earth leakage protection on the RCD protected side of the unit. The cost of these units has fallen significantly in recent years and you can often pick them up as a kit. You can often find a 12 way split load consumer unit with 10 assorted MCB's for between £50.00- £80.00. When buying a new consumer unit it is advisable to get one that has more capacity than you require and then you can add to it at a later date.
Consumer units that are fully RCD protected are available but could be dangerous, if the RCD trips for a fault or a nuisance trip it will cause the electricity to all the circuits to be isolated. This means that the lights will go out and you could be plunged into total darkness! For this reason split way consumer units are preferred.
The latest consumer units have twin RCD's which offer earth leakage protection to circuits on either side of the consumer unit. Another option is to use RCBO's which is a MCB and RCD combined into one unit.
| Before working on any electrical circuit you must ensure that it is isolated correctly and cannot accidentally be switched back on. Please read the article on safe isolation procedures before doing any electrical work. If you are not 100% certain what you are doing call a qualified electrician. Building regulations are changing all the time and modifying your home electrics could be against new rules and could invalidate your home insurance, if in doubt check first! |
This is the consumer unit with the visor open, which exposes all of the switches. From left to right they are- Main switch, 5 mcb's (non RCD protected side), Blanking plates, 5 mcb's (RCD protected side), RCD (residual current device) At each side of the unit there are two screws. The Electricity must be isolated and the cover only removed by an electrician or Competent person.
1. Main Switch - This is a double pole switch and is often rated at 100 Amps. Isolating this switch means that all circuits will be isolated, But the Meter tails which connect from the meter to the consumer unit are still live! 2. DIN Rail - This is a rail that is sometimes called a Top Hat rail, Normally these are 35mm wide. This rail holds all of the MCB's, you can also get time clocks and doorbell transformers which mount onto the DIN rail. 3. RCD - Residual current device sometimes called an Earth Leakage Circuit Breaker. An RCD is designed to offer protection against electrocution. Whilst having an RCD can offer some protection from electrocution it does not guarantee that you will not get an electric shock, but it may be very unpleasant rather than fatal. An RCD will not offer any protection from a Live- Neutral shock! Switching off the RCD will ONLY ISOLATE THE SUPPLY TO THE RCD SIDE OF THE UNIT! 4. Neutral bar- ( Non RCD protected side ) This is the terminal where all the neutral wires on the non RCD protected side of the consumer unit are wired. 5. Neutral Bar - ( RCD Protected side ) This is where all the Neutral wires from the RCD protected side of the unit are wired. 6. Earthing Bar - This is where all of the Earth wires are wired.
This is what a split way consumer unit could look like with the MCB's removed.
In some consumer units the MCB's will simply lift off the DIN rail once the screw holding it to the busbar has been unscrewed. Other MCB's clip onto the rail and require a screwdriver to pull back on the spring mechanism. Insert the screwdriver as shown here and gently lever downwards whilst gently pulling on the MCB from the bottom.
