Totally Tech

Q:When we were replacing the accessories within the property we came across red and black conductors at the sockets and red, blue and yellow conductors at the switches. The earth conductors at all the accessories are bare copper without any sleeving. Do we have to install sleeving to all the conductors to the modern standards?
A: These cable colours were in use until 2006 when the “new” style brown and blue coloured cables.

Q: A colleague has stated that to prove socket-outlets work correctly all we need to do is to plug in a socket-outlet tester which lights up to show the earthing is satisfactory. This would save on expensive test equipment and time spent testing, is this correct?
 A: The short answer is NO, these socket testers do not confirm the effectiveness of the earthing of the installation. There have been recorded instances where although these socket testers have indicated an earth is present the actual recorded value has exceeded the maximum permitted value for the earth loop impedance.

Q: We are carrying out alterations to existing circuits and have come across open connector joints at the rear of the kitchen base units, can we leave them in place?
 A: No, Live conductors and terminals are required to be provided with an enclosure to ensure there can be no access to those live parts without a means of a key or a tool to prevent the risk of electric shock. There is also a further requirement that the enclosure has to prevent the spread of fire in the case of a fault.
 

By Frank Bertie NAPIT Group Technical Director - Question: During a refurbishment of a kitchen we came across copper sheathed cable supplying the accessories. The existing accessories have boxes with metal clamps which are securing the copper sheath cable terminations. The accessories are being relocated and we will have to alter these cables how do we do it or can we replace the cable with twin and earth cable?

By Frank Bertie NAPIT Group Technical Director  - Q: When we were replacing the accessories within the property we came across red and black conductors at the sockets and red, blue and yellow conductors at the switches. The earth conductors at all the accessories are bare copper without any sleeving. Do we have to install sleeving to all the conductors to the modern standards?
 
A: These cable colours were in use until 2006 when the “new” style brown and blue coloured cables.

Q&A By Frank Bertie NAPIT Group Technical Director - Q: When we are working on circuits which are supplied from an existing consumer unit what procedures should we take to work safely?
 A: Firstly, it is a legal requirement that employers must ensure that their employees working on electrical equipment are competent to do so.

Q&A By Frank Bertie NAPIT Group Technical Director - Q: Do I have to provide grommets in metal back boxes of sockets and switches?
A: Grommets or some other method of protecting the cable from the effects of abrasion from the sharp edges of metal consumer units, enclosures or back boxes.
Care should be taken when the protection is installed as often during the installation process the grommets can move and either fall down or pull up leaving the cables open to damage. This is even more important when using grommet strip as this is more susceptible to movement.
 

Q: A colleague has stated that to prove socket-outlets work correctly all we need to do is to plug in a socket-outlet tester which lights up to show the earthing is satisfactory. This would save on expensive test equipment and time spent testing, is this correct?
 A: The short answer is NO, these socket testers do not confirm the effectiveness of the earthing of the installation. There have been recorded instances where although these socket testers have indicated an earth is present the actual recorded value has exceeded the maximum permitted value for the earth loop impedance.

Q&A - By Frank Bertie NAPIT Group Technical DirectorQ: We are carrying out alterations to existing circuits and have come across open connector joints at the rear of the kitchen base units, can we leave them in place?
A: No, Live conductors and terminals are required to be provided with an enclosure to ensure there can be no access to those live parts without a means of a key or a tool to prevent the risk of electric shock. There is also a further requirement that the enclosure has to prevent the spread of fire in the case of a fault.

The New Fuse Standards and the Maximum Zs Tables
by
Bill Allan
Amendment 1 of BS 7671:2008 contains some important changes concerning new fuse standards which took effect in March 2010. These changes can be seen in the maximum earth fault loop impedance (Zs) values in Tables 41.2 and 41.4. (Table 41.3 concerns circuit-breakers) The new fuse standards are:
 

BS 88-2 which has replaced BS 88-2.2 and BS 88-6.

BS 88-3 which has replaced BS 1361.