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SPLIT LOAD

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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.

 

All electrical pages are for information only! New rules have been introduced for electrical safety in the home, please read this document by clicking here, before starting any electrical work

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!

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.

Split Load consumer units are probably the safest type of consumer unit available today. 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. 

   

Split Load consumer unit

 

consumer unit with visor closed   This is what a split way consumer unit could look like when the visor is closed.

 

consumer unit with visor open   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.

 

Split load consumer unit with cover removed

 

  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.

 * Bars are often caller Terminals.

Which circuits go on which side of the split load consumer unit-

 

NON RCD PROTECTED SIDE RCD PROTECTED SIDE
Lighting Circuits Electric showers ( this is not Mandatory, but advisable)
Electric cookers, unless they have a socket outlet in which case they must be wired to the RCD protected side. ( electric cookers often cause nuisance tripping and are therefore wired to the non RCD protected side, unless they have a socket outlet) All sockets that could have outside equipment plugged into them.
Extractor Fan A socket in a room with a shower cubicle
Fire Alarm  
Smoke Alarms  
Freezer Circuit ( as long as the freezer is wired into a switched, fused connection unit)  

 

The bottom of the MCB's are connected on the non RCD protected side of the unit to the Live terminal of the Main switch via a busbar.

The bottom of the MCB's are connected on the RCD protected side of the unit to the live terminal of the RCD via a busbar.

Busbar

The busbar will normally come in one piece and will require cutting using a hacksaw or similar. There is a minimum separation required between the two busbars to prevent arcing, in some cases this is 7mm. It is a good idea to cut off an unused ways from the busbar as a new busbar can be purchased if needed.

 

busbar cut to size   This busbar has been cut for a split way consumer unit that has 4 MCB's on the non RCD protected side and 6 MCB's on the RCD protected side.

 

 

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.

 

   

Split Load consumer unit

 

 Almost Bare consumer unit   This is what a split way consumer unit could look like with the MCB's removed.

 

How to remove the mcb's   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.

 

Busbar in position   Here you can see that the busbars are in place and that the unused ways have been removed from the busbar.

The bottom terminal screws which secure the busbar need tightening to the specified torque by the manufacturer.

Consumer unit wired

This consumer unit has been partially wired and requires the meter tails to be connected. This has been a replacement unit and so it is often difficult to change a consumer unit without having to join the wires.

 

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You can see from the picture that all the earth wires are sleeved and connected to the earthing bar. 

 

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There is only two circuit breakers being used on the non RCD protected side of the unit, the other two are spare.

 

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On the RCD protected side of the unit there are 4 circuit breakers in use and two spare units.

 

The finished item   When the cover is replaced the two spare ways in the middle are covered by blanking plates.

The circuits are then identified by stickers placed beneath each MCB.

 

 

 

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