Hi. I would appreciate the thoughts/experience of the users of this forum. A client of mine has just purchased a whole stock of 10-way extension lead towers because of the amount of electrical sockets needed in each room. My initial reaction was that we are trying to get away from extension lead use (because of the associated fire hazard problem) but on inspection these items have BS1363 and BS5733 marked on them and state they are 'Surge Protected'. Research has found that these are quite wide specifications for general electrical safety and have been around some time. My client is satisfied they are safe and I am finding it hard to argue at this stage (as the cost of providing proper sockets would be very pricey). Does anyone have anymore experience/knowledge in this area to know if these electrical towers are a possible fire hazard. Is there any evidence that they are unsafe to use or any respected advice that gives further information? Regards, DaveB

Don't like them, personally, end of. Small overloads of long duration are a large risk in fixed installations as many designers and electrical contractors are not competent to assess these, and clients have a serious habit of introducing such overloads by using such stupid devices, after the installation has been designed & installed. I'd ban them all given a chance.

Simple answer this one. Have an electrician run a load check on the circuit/circuits feeding the system. As I said, simple :-) Re Towers, ok if installed, tested and loaded correctly, but as Paul says, wide open to abuse and I've seen this more than once, :-) have fun. P.S. Please ote that Zs/Vd if added to ringmainfinl sub-circuits Llike Paul, I'm not keen o them unless installed by competnt people (Eletrians)

achrn, I disagree. Take your example, 2 x 1.5A = 3A + 2.5A + 0.2 + 0.15A = 5.85A Your colleague at the next desk has the same and works the same hours as you so that is now 2 x 5.85A, into the same socket outlet. That is 11.68A, this is very close to the maximum rating for many cheap 13A twin socket outlets which are actually only rated at 13A combined, from both sockets. Do this twice in the office and you have 23.36A Stick another one on and you have 29.21A this is more than the current rating for 2.5mm sq flat twin & cpc cable clipped direct. Now allow for a little more load elsewhere and you could easily top 34 perhaps 35A. On a cable rated at 24 perhaps, with a circuit breaker perhaps rated a 32A, it will carry 34A for a very long time. This is a valid design for a ring final circuit as you have the load shared in both "legs" of the ring. To calculate the load balance you would need much more information than we have here and you would need to enlist the help of My Kirchhoff,. There could be a few derating factors on the cable, grouping or something, that could easily cause issues. You seem to be only considering the load on the extension, that was, and is not my point. There has been a test undertaken recently under controlled conditions by one of the labs, where by single 13A rated socket outlets were put under test at 13A for 10-12 hours, typical charging current/time for an electric vehicle I gather, I've not bothered to investigate this technology yet. The results were worrying, not one of the cheap n cheerful, or the expensive branded sockets came out unscathed IIRC, there was certainly damage on some of them, and these were items which apparently met the requirements of the relevant standard. With many offices working 10-12 hours per day if not more with systems that were not originally designed to take such loads then there could, be issues. I've investigated a near fire in a premises, which if the fire had gotten hold, would have been a total premises loss. The reason, a unit which had been fiddled with by incompetent persons unknown, who had changed settings elsewhere on the system, and increased the load on the circuit to just over 14A on a 13A fused connection unit (FCU, commonly but incorrectly called a fused spur). The unit got very hot and overheated, however, it was the same design as you would have at home, and was not really correct for the environment, but, the installation was old... As Zimmy says, perhaps load checking is required, diversity is a wonderful thing, but, there is now a definitive requirement to avoid such small overloads that last for considerable time as they have been found to be very damaging.

Hi All, Thanks for all the input from everybody which is most appreciated and has rather confirmed my own thoughts. I'm really not keen on such over use of extention sockets and to have a 10-way tower just invites people to use every one of the sockets. The thought process is if they are allowed to construct such a thing with 10 sockets then it must be ok to use them all. The fact that they are also empbossed with BS numbers, whilst a useful pointer, leads people to believe they are safe to use in any situation. After Paul has so eloquently explained the technical aspect I will certainly be advising my client to a) get their system checked by an electrician b) advise them to provide proper sockets which are fitted to the main supply. Thanks again, Dave.

achrn, Once again we disagree. I do not feel that my point is irrelevant. How can the installation be well within it's design current demands if there is now a requirement for multi way extension adaptors. Just because in the past PC's required greater current demand, then the install if competently designed would have allowed for such demand, thus there would have been more than a single twin socket outlet per workstation. Multi-way extension adaptors encourage abuse of the fixed installation, I don't see how you can justify that. There is no real control over what is connected to them. In my experience I believe that if the data was available the power consumption has increased as well as the 3rd harmonic component. I fail to see how you can state that adding sockets cannot increase the power consumption. Whilst socket outlets themselves consume no power, the items that can be connected do. Thus there is the increased possibility of fire due to the possible uncontrolled use of these sockets. Finally, even though these multiway adaptors may well have BS markings, there are issues and loop holes in this approval process that are in debate within the industry. Take any linear multi way adaptor, can you insert the 3 pin plug upside down, such that the earth pin enters the earth pin and opens the shutters on the L & N pins, with nothing inserted into these receptacles? If so, do you consider this safe as it defeats one of the most fundamental safety features of the BS1363 socket outlet? If you do please state categorically that you do, and state that you are prepared for such items to be used in environments that you are "responsible" for. That way we know where you stand. This is another segment of the "multi way" argument that must be considered.

I wonder if the cheap socket outlets are made by the same firm who supplied all those Crabtree Wylex etc mcb's that were rated at 6,10,20,32 amp a while back. You know the ones... The ones that had to be replaced as they had no over current protection and when stripped apart that were just switches? They were imported and rated and had BS/EN stamped on them. You know the ones, the cheap ones that were rated at ,6,10 etc. Just like the 13A socket outlets.... Paul said it all. We were there!

As I said. Make a load check of the circuit. If the load is excessive install new circuits (system permitting). Please remember that a lot of electronic devices use the earth system as a functional earth (switching). Care must be taken then to ensure that the original intended use for the circuit is not compromised. If rcd protection is at source then the leakage current MUST not exceed 25% of rated trip current. These items will also place a lot of current whizzing down the installation earth conductor. Perhaps the circuit would need to be connected back at the dist board with each cpc in a separate earth terminal? The socket outlets wired as per cpc in on one terminal and cpc out in the other... I hope my point is getting through here. A warning sign may be required. My money would be on getting an VERY GOOD electrician to look at the system. Ask Paul to take a look is my advice :-) You could do an awful lot worse! Other than that close this thread down.

How exactly would they manage that, then?

It was of course other devices such as computers. Tell you what, forget it. Some of you are simply not worth the effort. Your not worth the trouble to be honest. Have fun :-)

The scenario is my office location, where I stated that the need for extra sockets related to items like mobile phones and tablets, with low current demands. Zimmy subsequently said "These items will also place a lot of current whizzing down the installation earth conductor." I asked what he meant by that statement. I'm still waiting for an answer. I don't believe that multi-way extensions themselves or mobile phone or tablet chargers, or any of the similar low-current double-insulated devices under discussion, place a lot of current whizzing down the earth conductor. I'd be very please to receive a believable explanation of definitive reference that they do so, but it's going to have to be remarkably compelling evidence, because it flies so completely in contradiction of my understanding of electricity.

1 to Dave If the load stays the same then use them if you have to. The problems start when people see a few extra outlets and start to fill them We've seen items such as kettles etc used on computer circuit. Honest, true. Swansea city traffic light computer system loaded with 3No. Kettles! Best to use a 32A radial to feed the towers. One mcb/rcbo per circuit (NOT a ring main as these are more trouble than they are worth). Computers (towers) tend to use factional switching for operations hence the reduced leakage to earth. With such circuits on rcd/rcbo not more than 7.5mA per 30mA rcbo. If you have 10 outlets to start with and your circuit load is 20A then not a problem. Why not get someone, perhaps achrn, to wire one or two new circuits in for you. Oh and Achrn, are you a pancake chef? :-) You need a happy pill mate and I can think of somewhere for you to put it :-) In your mouth of course And mods, if you do pull this please, please don't bother emailing me. With clowns like achrn about I couldn't care less. Paul has more staying power than me :-)