Posted By Nick House Hi all Can anyone confirm whether the maximum permitted length of an electrical extension lead is 1.5 metres (this rings a bell with me). If this is correct, can anyone tell me where I can find a reference to this (I've looked through the Electricity at Work Regs, but it doesn't specify in any great detail)? Thanks in advance Regards Nick.

Posted By Alec Wood No there is no 1.5m limit, however the use of extension cables should be discouraged or tightly controlled, not least because of the trip hazards that they invariably introduce. Sometimes it is safer to use an extension lead to bring power to the job, sometimes not. The problem with long cables is some users have a habit of leaving the extra length they don't need coiled up, which reduces its current handling capacity because it causes the cable to heat up more than would normally be expected. The point raised in the above in regard to daisy chaining is interesting. I had this discussion with someone who wished me to pull the rug out from under some contractors on our site recently. Exhibitions of the line of small booths type, such as job fairs and the like, are often supplied with power by daisy chaining four way extension cables between booths, so that each booth gets three sockets, one being used to supply the next booth in the chain. These chains are then supplied via extension cables, protected against damage by standard cable protectors, from the wall sockets of the room. I've seen this happen a lot - my impending departure has prompted me to visit many of these fairs - and a similar event took place in premises we share recently. Sets of four booths were daisy chained using 4-way blocks connected by 13A cable. Each block was PAT tested before connection, inspected and the fuse ratings checked. From an electrical safety point of view such an installation has several issues against it, not least is that it appears as a multi-outlet spur instead of a ring so there is a higher risk of any one outlet having its earth compromised. That said, such an installation is temporary, the conductors at all points are of sufficient current handling capability, the fuse ratings are appropriate and RCCD units are in use, both in the board and on each wall socket, everything has been thoroughly examined and tested before use. Permit or not? In consultation with our maintenance manager (an electrician) I did a risk assessment and permitted the installation above to be used for the six hours it was needed, with some extra controls. Not everyone agreed this was reasonable, but all the electricians did! Extension cables will always be a source of debate, but banning them is never the answer. Alec Wood Samsung Electronics

Posted By jom What about damage to the internal insulation from crushing? Is this something members of the public do not understand? Last week at a market I saw a truck parked on grass with a front wheel firmly on top of a lead. It was a "heavy duty" lead, ie more robust than a domestic lead. It doesn't appear that this would cause external damage, but it might destroy the internal insulation, yes?

Posted By John Webster OK Alec My statement never to daisy chain extension leads should have been qualified by "unless the installation is checked by a competent person". John

Posted By JAMES MM Nick I believe that there is some confusion with your question. Do you mean the length of the lead attached to the appliance or the length of an extension lead?

Posted By Nick House Hi all Apologies for the delay in responding, but I've been out of the office for the last few days. The proposed lead would be for powering one laptop and one 17" LCD monitor in a sealed display case (sealed as in locked for security purposes, but there will be ventilation for heat dissipation). The closest power outlet is 3 metres away. The proposal is to plug in a surge protected twin outlet extension lead which is 3 metres long. This will be attached to the wall above floor level, and will run under 2 other display cases before reaching the intended case. This would then alleviate any trip hazard. Unfortunately, it is not possible to use a case closer to the power outlet. The socket end of the lead would be mounted on the underside of the case, so that the machines could be unplugged quickly should this be necessary, with the leads to the equipment being routed through the ventilation opening in the back of the case, and into the machines. I realise that the ideal solution would be to have another power outlet installed underneath the case, but this is not really an option - hence the lead question. Regards Nick.