What is important to look during this inspection?
In general terms we are inspecting the installation with regard to personal safety, equpment age, deterioration, equipment corrosion and overload.
Suitability and external influence to the power system should also be included. At this point it is a good idea to get from the client any documentation that is relevant to the installation (like plans, drawings, previous test results and certification/if any, fuse charts and so on.
You should also make it clear that you will require access to all parts of the building and that the electricity supply will need to be turned off at some point. It is also a good idea to ask the client if they are aware of any alterations that have been carried out, as this information may be useful to you during inspection.
The first part of a visual inspection is to ensure that the system is safe to test and that you have enough information to be able to carry out the test safely.
Generally, a good place to start would be the supply intake; this will give a reasonable indication of the age, type and size of the installation.
Checking the supply intake
Things to look for at the supply intake before removal of any covers would be:
- The type of power supply system – is it TT, TNS or TNCS?
- Are the conductors imperial or metric?
- What type of protection is there for the final circuits?
- Is documentation available for the original installation? (Very important!)
- Is the consumer’s unit labelled correctly?
- Is the earthing conductor in place?
- What size is the earthing conductor?
- Is the earthing conductor green or green and yellow?
- Are all of the circuits in one consumer’s unit or are there two or three units that need combining?
- Is there any evidence of equipotential bonding? Remember! It must start at the main earthing terminal.
- What size is the equipotential bonding? Is it large enough?
- Is there a residual current device (RCD)? If so has it a label attached? Is it a voltage or current operated type?
- Do the enclosures meet required IP codes? (Regulation 412-03-01)
- If alterations have been carried out is there documentation available for them, along with test results?
- What size is the supply fuse? Is it large enough for the required load?
- Are the meter tails large enough?
- Are the seals broken on supply equipment? If they are it could indicate that the system has been tampered with since it was first installed and perhaps closer investigation is required.
- Have any alterations or additions been made?
- Would any alterations or additions affect the required disconnection time for the circuit concerned?
This list is not exhaustive and installation conditions may require more. When the visual inspection of the supply intake area is complete, that is a good time to look around the building to make sure that there are no very obvious faults.
All of this should be carried out before removal of any covers.
Things to look for:
- Are accessories fixed to the wall properly? Are they missing or damaged?
- Are the accessories old with wooden back plates?
- Are the socket outlets round pin or square? Is there a mixture of both?
- Have cables been installed in vulnerable situations?
- Have cables, enclosures and accessories been fixed securely?
- Have ceiling roses got perished flexes? (Particular attention should be given to the old braided and rubber type flexes.)
- Are any socket outlets likely to be used outside? If they are then they should be RCD protected. If they have been installed before the late 1990s, then it is not a requirement that they are, but an RCD should be listed as a recommendation.
- Are earthing clamps to BS 951 standards and correctly labelled?
- If gas, water is bonded using the same conductor, ensure that the conductor is continuous and not cut at the clamp.
- Is the supplementary bonding in place in bathroom?
- Is the correct equipment for the correct zones in bath/shower room? (See 601 BS 7671)
- Has the bedroom had a shower installed? If so, are the socket outlets 3 metres from the shower and RCD protected?
- Is there any evidence of mutual detrimental influence; are there any cables fixed to water, gas or any other non-electrical services? (The cables need to be far enough away to avoid damage if the non-electrical services are worked on.)
- Are the cables of different voltage bands segregated? Low voltage, separated extra low voltage (SELV), telephone cables or television aerials should not be fixed together (although they are permitted to cross).
Whilst these items are being checked, look in any cupboards for sockets or lights. If your customer is uncomfortable with this it is vitally important that you document any areas that cannot be investigated in the extent and limitation section on the Periodic Inspection Report.
Clearly, if it is an old installation, an electrical installation certificate must be completed and some of the items listed above will apply. However, if it is a new installation, access to all areas must be secure; if this is not possible then the certificate should not be issued. Again, this list is not exhaustive but will not require removal of any fittings, etc.
Providing that you are happy that the installation is safe to tamper with, a more detailed visual inspection can be carried out and the dreaded but necessary form filling can be started.
Once again begin at the consumer unit. Before you start, this must be isolated. The Electricity at Work Regulations 1989 states that it is an offence to work live. Once you remove a cover you will be working live if you do not isolate it first.
- Your first impression will be important – has care been taken over the terminations of cables (neat and not too much exposed conductor)?
- Are all cables terminated and all connections tight (no loose ends)?
- Are there any signs of overheating?
- Is there a mixture of protective devices?
- Are there any rubber cables?
- Are there any damaged cables (perished or cut)?
- Have all circuits got Circuit Protective Conductors (CPCs)?
- Are all earthing conductors sleeved?
- On a photocopy of a Schedule of Test Results record circuits, protective devices and cable sizes.
- Look to see if the protective devices seem suitable for the size cables that they are protecting.
- Note any type D or 4 circuit breakers – these will require further investigation.
- Are all barriers in place?
- Have all of the circuit conductors been connected in sequence, with phase, neutral and CPC from circuit number 1 being in terminal number 1 – preferably the highest current nearest the main switch?
- Have any protective devices got multiple conductors in them, are they the correct size (all the same)?
- Is there only one set of tails or has another board been connected to the original board by joining at the terminals?
Resource: Inspection, Testing and Certification of Electrical Installations by Christopher Kitcher (buy the book at Amazon)
Please can you send me the standard which recommend the period of visual inspection for outdoor electrical main distribution board.
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