Don't sound right to me. There must be an exception for supplying fixed loads via a fcu? I refuse to believe the IEE would make us use more copper in these resource hungry days when less would would just as well.
I've read with interest, the comments on this post and would like to add a few of my own. It is recommended that loads of 2kW and over are supplied on the own circuit, this is to avoid sectional overloading of a given circuit. Regarding supplying a boiler and immersion heater from the same circuit is, quite frankly, poor design. 7671 clearly states that a power failure of one circuit should not adversely affect that of another, causing inconvenience. If the MCB where to go on an immersion heater circuit (which incidentally should be fed via a Double Pole Switch, fused or otherwise) then you have lost both sources of heating water. Depending on the heating setup, it is possible to still have a reduced level of central heating using only the immersion heater, which in winter is not a bad thing. Regarding using 1mm from a Fused Spur, this does not comply with the Regs. 1mm has an "IT" of 11 amps, it is possible that someone can come along and replace a fitted fuse with a 13amp fuse, hence giving rise to potentially, overloading the cable. Regarding the comments on here stating that 1mm is only to be used for lighting circuits, I honestly do not know where you get that rubbish from. Provided that a circuit is designed properly 1mm cable can be used on lighting sockets, outdoor supplies etc. etc. etc. It is also incorrect to believe that 1mm can be used on lighting circuits per say. As stated 1mm has an "IT" of 11amp, when this is run through 500mm of thermal insulation, which is common now, then the cable is derated by 50% meaning that using a 6a MCB is technically overprotection for the cable. A 5amp MCB or even 4 amp MCB should be used (common in the MG range). It is also good practice to load a circuit at no more than approximately 75%. To answer another comment on here, yes we are indeed supposed to be competent persons and, in being one, is not only a case of deciding what is safe but also, what is good engineering practice. Connecting 1mm from a spur is not good practice. As has been suggested 7671 is not statute, it is true that they are not mandatory, however, to comply with 7671 would be deemed by a Court of Law, as complying with the Electricity at Work Act, The Electricity Supply Regs and The Health & Safety at Work Act, which are all, statutory. It you did not comply with 7671, you would have to be able to demonstrate the practicalities of your actions and non compliance. In respect to senecas comment regarding the 2.5mm feeding a socket on a 32A MCB, the reason why this is OK is because in proper use, a double socket can only take 26A, i.e. 2 times 13 amp plugs. Protecting a 2.5mm cable with a 32A MCB, Lectrician, is not protecting the cable, no matter what the NICEIC assessor says (I can only assume that the said assessor was only Part P which is a joke), depending on the Zs of the circuit it is possible to damage the cable (particularly between Live and Earth) after the MCB but before the Fused spur causing a low resistance that would result in gradual overload and over heating, potentially causing a fire (which has happened twice in the last 12 months) before the MCB tripped. One would only hope that the insulation around the Neutral would break down first resulting in a power outage. Unfortunately, although it does happen, circuits are not supposed to be designed on "hope".
Hi B. I've only read your long post once so I'm not 100% sure if I'm right but 1. 1mm cable will carry 11amp if 100% covered in insulation so a 6a mcb is fine. I did look into this a while back so I'm pretty sure i'm right. It's method 103 I think. 2. Agree 1mm used on a ring for spuring is a no no. 3. The law and bs7671 are a bit of a mess. I don't think you could use 7671 in a court as it is non-stat. A better way would be to use the laws concerning negligence, and then bring in bs7671 as a yard stick, but no case law has ever come up as far as i know, so it's a grey area. Lec said the 2.5mm was a fixed load, so fine imo. Problems when adding sockets to the load though
Seneca I suggest you read it again my friend, nowhere in the regs does it state that 1mm is specifically for lighting (see sec.5 GN1). It can be used for any application provided that the circuit is suitably designed. Going "through" thermal insulation for more than 500mm derates by 50%, not covered by and that assumes one side is touching wood, brick, plaster board etc .etc.Reg 523.9. Regarding 7671, I did not say that a Court would use 7671 against you what I said was if you complied with 7671 a Court would accept that you have complied with the Acts of Parliament I mentioned, however the Judge may also bring into question your experience and knowledge before himself, deciding whether you are competent or not. Let's not fool ourselves, you may have passed an exam, that in itself, does not make you a competent person. Lec said 32A MCB protecting 2.5mm cable, also the "Fixed Loads" are by definition prone to overload, that is why fused spurs are required. That does not detract from the possibility of damaging a cable between DB and the load. It does not matter where you use the 1mm from, unless the circuit is designed and protected at less than 10A. It is the output cable from the Fused spur that has to be a minimum of 1.5mm app 15. Point to note, an Electrician was prosecuted earlier this year for causing the death of a woman in her apartment, the Judge cited "the installation did not comply with BS7671 and therefore could not comply with the Electricity Supply Regs".
Not sure if your trolling but if you killed someone due to your "negligence" then that would be the law you would be tried under. bs7671 might be used as a yardstick but really it's all to do with "who is to blame". For example, I might do a pat test on a washing machine, delare it safe only to find later a manufacturing fault has caused a fire. Who is to blame? I wouldn't think it was me.
Beau007. You need to read the regs and learn the difference between overload and short circuit current, and understand what 'IT' is. You spout ******.
Beau007, Minimum cross sectional area of conductors, Big Green Book, Table 52.3, page 130. 1.00mm lighting.
And 1.5mm for "power ctts". I mean, wt actual f? That must be the most stupidest, ******* thing the IET have EVER come up with. I do smokes in 1mm, like 60m ctts in 3 core, so now I have to do them in 1.5mm???????? WHY?
I agree it's daft Col, after all if a circuit is protected by a 3/5 amp fuse what does it matter what it's feeding? It sounds like the IEE are making it just two categories, lighting and power.
Starting from the top. chippie 244, no I am not. The case in question was the so called "electrician" ran cables through a C track wall system without Earthing or RCD protection, the plasterer when affixing his boards screwed through the cable earthing onto the C track. The wall was soaked due to a water leak which made the wall live. The woman was subsequently electrocuted as she touched the wall and a radiator simultaneously. Coloumb, under The Health & Safety at Work Etc Act 1974, as you declared the appliance safe in a subsequent test to that of the manufacturers, then you would be liable. Lectrician, senario for you, just like above, someone holes the 2.5mm cable that you have backed up by a 32 A MCB and it results in a low resistance, this then overheats and causes a fire. Technically it is an overload as a short circuit is defined as a fault of negligible resistance, make sure of your facts before trying to deride someone. And as far as "spout ******", I've read some of your previous posts, I suggest you my friend, do the same. You're not as knowledgeable as you think you are. Seneca, I suggest you read the posts again and then go back onto a design course, nowhere does it state that 1mm is "specifically for lighting". The table you refer to states that 1mm is the MINIMUM. seneca again, the reason why the regs state 1.5mm from a fused spur is because once it has been installed there is nothing preventing anyone in the future, replacing the 3 or 5 Amp fuse with a 13 amp. And before some D*head says that someone could put silver foil across, it is the design, installation and techniques used that comes under scrutiny in a Court Case. You have a duty of care to ensure your circuits are DESIGNED properly and safely. And as far as the comment on "New user syndrome", let me explain who I am, I am an Electrical Engineer a proper one, not someone that has done a couple of months at college under C&G claiming to be an engineer. I have been a Design Engineer for the last 25 years and three of my systems that I designed are still market leaders. In my 35 years in the Industry I have seen numerous know it alls come and go. I have lived and worked in virtually every mainland European Country and worked in establishments ranging from Opel in Frankfurt, the Bundesbank and Hamm Nuclear Power stations, not to mention my time in central and eastern China working as a trouble shooter for two of the largest Plant manufacturers in the World. II am a chartered Engineer and also an Expert Witness for the Court and reading the comments on here lead me to believe that you are incapable of designing circuits properly, are unable to interpret regulations and probably not able to put batteries in a torch properly or without written instructions. You may be tradesmen, but none of you will ever be Craftsmen. Don't bother responding because I won't be wasting my time coming back here.
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