17th Edition Distribution Board

Upgrading an old consumer unit to one incorporating two residual current devices (RCDs) as shown in the image below, is a job that many people will now have to consider. The 17th edition of the wiring regulations requires most circuits in a domestic property to be protected by an RCD. It is often a better and cheaper option to upgrade the consumer unit rather than alter the existing installation in order to comply with the new regulations. 

Swapping the consumer unit may also involve some additional electrical work, to enable the installation to meet the standards set by the new wiring regulations. This might include splitting circuits or running in new cable. An older property might have all the lighting and sockets supplied by just two circuits. It would be better practice to split these so that the lighting and sockets for each floor are on separate circuits with their own circuit breaker. Other problems that require attention include borrowed neutrals. This is where a neutral return path was not available and a link to another circuit has been made. Correcting this fault would, in many cases, require a new cable to be laid back to the consumer unit.

Checking earthing and bonding arrangements
Before the consumer unit is changed, the electrician will have checked the distributor's equipment at the origin of the installation and the earthing and bonding arrangements. This is to ensure that they are safe and that they comply with the regulations. Many older properties do not have a double pole isolation switch between the meter and the consumer unit meaning that the electrical distributor will have to be called in before work on the consumer unit can start. The distributor may oblige by installing this main switch.

Most domestic properties have the following arrangement at the origin: the service cable entering a sealed unit with a fused line (live) conductor with a 100amp main fuse or service cut-out, 25mm meter tails, a digital or analogue meter, 25mm tails to consumer unit. It is here that the main switch would be placed. The ‘automatic disconnection of supply' would be provided for by 16mm earthing conductor and 10mm main bonding conductors to gas, water and other services. These arrangements vary with larger or smaller installations; your electrician will advise you on what is required.

Installing the new consumer unit.

The nature of this work, disconnecting the overload protection and connecting the cable to a new means of basic and fault protection means that the electrician will have worked on all circuits. He will therefore have to conduct an electrical test on all circuits to ensure that they are safe and will then have to issue an electrical installation certificate before the job is handed over. Any faults found on a circuit will have to be corrected before the circuit is energised.

Safety Note

Building regulations are becoming stricter, requiring that competent persons only carry out electrical work, with most works having to be notified to the local authority. Modifying the electrical installation in your home could be against the new rules and could invalidate your home insurance. 

RCDs (residual current device)

Unless the fault is caused by an RCD tripping (please see below) due to the many problems which may occur within a socket circuit it is always best to get advice from a qualified electrician. Please feel free to contact us for further advice and guidance.

RCDs are designed to trip off in the event of an earth fault much quicker than a fuse can blow or an MCB can trip, this therefore makes them ideal for providing protection within the home against electrocution. Most modern wired homes are now fitted with RCDs and these can sometimes trip. Your RCD may be built in to your mains board or it could be fitted in to a separate box, an RCD can be identified by the "test" button which is normally built on to them. If your sockets or lights stop working and you notice that your RCD has tripped reset it, if it remains on then there is nothing further you need do, but if it trips again unplug all the appliances in your house and try to reset it again, if it does not trip plug in each appliance again until it does trip, you then know that the appliance you just plugged in is causing the RCD to trip, this appliance is most probably faulty and should be checked by an appliance engineer. If it still continues to trip with everything unplugged and call us. Some appliances in particular can cause RCDs to trip, irons, kettles, washing machines and any garden equipment, this is because of the presence of water, any appliance that causes the RCD to trip should be inspected by an appliance engineer before being used again. The RCD should be tested at regular 3 month intervals by pressing the "T" or "Test" button, this should cause the RCD to trip, just reset the RCD as normal, if the RCD fails to trip please call us on: 07758 514381 or email Help@weeltd.co.uk .

Everybody knows that appliances wear our over a long period of time, but most people just assume that the wiring within their home is in a safe condition, why would they think otherwise, everything is working just like it always has done. The answer may be yes it is working, but this does not mean its safe. Over time we have invented more and more appliances and older installations were simply not designed to cope with the new demand, in your average house wired in the 1960's just one single socket and one light was fitted in each room, compare that to today when on average we fit around 3 double sockets, ceiling and possibly wall lighting in each room.
The type of wire used in older installations was insulated by rubber, paper or cotton; this insulation will have over a period of time degraded and possibly in some cases become detached from the conductor causing a serious fire/electrocution risk.
The purpose of periodic test and inspection is to check all of the wiring within your home is safe and Identify any things that could cause a possible problem in the future, the wiring in your home should be tested at a period not exceeding 10 years or at every change of hands, which ever is sooner. By testing at regular intervals you guarantee that your installation is safe and meets the current rules and regulations. Proper testing involves taking readings using test instruments and having a general look at the condition of the installed wiring and accessories, before issuing a test certificate.

Below is a list of some common problems that we have found during carrying out basic periodic inspection and testing:

Old decayed rubber cable running over water pipes.

The rubber cable pictured right was found during a routine inspection and test during a house move, the client requested that we test the house prior to them moving in, the house was fully wired in old rubber cables which had badly decayed. This cable could have caused all of the pipe work within the house to become live; it also could have possibly caused a fire.

This house was fully rewired using modern PVC/PVC insulated cables before the owners moved in allowing us to complete the works with minimum disruption to the family.

Old very badly decayed cotton covered cables.

The cotton covered cables pictured right were discovered during a routine test and inspection, most of the property at some point had been rewired but just some of one lighting circuit had been left wired in the old cotton covered cables, the picture shows the cable as found at a lighting point, the insulation has nearly fully come off of the "live" (red) cable, this picture highlights the danger of old decayed cables, the missing insulation poses a risk of electric shock and fire.

The complete circuit was rewired using modern PVC/PVC cables.

Vermin damaged cables.

The cable pictured right was found during a routine 10 year inspection on a bungalow, rats or mice had gnawed away at the cable right down to the copper of the conductors, this cable presented a risk to anyone touching it accidentally if they went in to the loft, it also presented a fire hazard.

The cable was replaced with a brand new one enclosed in steel conduit to help protect it from further vermin attacks.

Old Wooden Fuse Board found still being used.

The wooden fuse box pictured right was found still in use on a house that had been recommended for rewire after an inspection and test. This unit did not meet the modern standards and offered poor circuit protection with the old fuse wire system, modern MCB circuit protection offers much safer protection. Modern split load consumer units also come with the added protection of an RCD unit which helps protect against electrocution.

The house has now been rewired and a modern slit load MCB consumer unit complete with RCBOs was put in its place.

Earthing too small and no longer meets the current regulations.

It is very common to test a house and find that earthing within the property does not meet the modern requirements and needs updating, this is due to the regulations changing as it is found that other earthing arrangements work better than existing ones. The picture on the right shows some modern bonding on a gas pipe just past the gas meter.

Thermal Image of socket adaptor

As electrical current flows through a conductor, heat is generated. Using our thermal imaging camera, electrical faults and potential system overloads can be detected weeks in advance by identifying inconsistant temperature variations on any given surface or electrical component. This will help prevent any unschedualed system shut downs. We use thermal imaging to detect abnormal temperature variations that cause common electrical faults, such as...

Loose/deteriorated connections - Overloads - Imbalanced Loads - Open Circuits - Inductive Heating - Defective Equipment - Faulty Wiring

Can't find an electrical fault? Contact us today for a thermal imaging inspection of your electrical distribution system! We can also conduct schedualed routine predictive and preventive maintenance progams in your workplace.

Please note: Thermal imaging inspections on electrical systems require a certified electrician or on-site maintenance officer to confirm readings with an ammeter or voltmeter.

Below are a sample of other heat source overloads.

• Distribution panels
• Fused disconnection units
• MCBs
• MCCBs
• Cable temperatures