You don't seem to always do that, as per:
Perhaps that has contributed to the fact that some people think it is necessary and required.
1 OR 1.5mm twin & earth cable for bathroom LED downlighters... discuss
- Thread starter rob4beer
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Point 1 - As a qualified electrician, I follow the cable calc process as standard practice. As you say in domestic installs, 1.0 is fit for purpose.
Point 2 - Yes, for lighting circuits 1.5 is used by rote.
Personally, I fit 1.0 in most cases but am happy using 1.5 if i have some available.
Not the full calc, but experience tells us most domestic lighting circuits could be wired in 1.0. If I see a CF is in play, I'll run through the calc. It's not difficult maths.
My answer was to the original poster, who I assume is not a qualified electrician.
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That's obviously the correct process (whether or not the installer is a qualified electrician). So why ....
I'm a bit confused - are you saying that the "lot of us" you referred to above does not include yourself?
Kind Regards, John
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You are very probably right (although I have occasionally seen or heard 'qualified electricians' exhibiting less knowledge and understanding than the OP has in this thread) but, nevertheless, one really should not 'assume'!
Kind Regards, John
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I would agree using simple mV/A/m it is reasonable easy, however once one starts to correct the mV/A/m then I would say rather complex, to install using simple maths is OK, however to criticise some one else's install one has to be sure so you have to use the correction, this was why I built the java script program, at the time I was worried about doing EICR and not highlighting a volt drop problem which is latter highlighted and having a claim for any work required to correct it.
However once I had built the program it became apparent the meters used to measure the loop impedance are not accurate enough, press the test button three times any you get three different readings. So unless wildly out it would be hard to show some one had got it wrong. The debate on this thread as to if the design current should be 6 amp or some lower figure means however accurate for a circuit with multi-loads throughout its length unless the designer states the design current then near impossible to show he/she got it wrong.
With the length of cable needed to get just 6.9 volt drop, in real terms it is very unlikely that you will ever get to the point where a light failure is blamed on volt drop due to cable length. I have seen where old fluorescent fittings rated 240 volt have failed when solar panels have been fitted in the area and the voltage dropped to 230 volt, however it is hard to prove as when the tubes age they get harder and harder to fire and to show it is actually due to volt drop and not age is hard.
I see a small problem in using 1.5 mm² as in the main triple and earth cable is 1 mm² so using 1.5 mm² means a change in the current carrying capacity of the cable so much easier to use 1 mm² everywhere.
Measure R2.
That's not the debate. We are querying your results.
Possibly true, but it is you who always raises the subject.
In a 'normal' house, it is probably rarely considered.
No, it isn't.
Why triple and earth?
Does that matter considering the OPD probably used?
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When I was an apprentice (mid- late 80's) , everybody in the house-bashing trade was using 1,5.
I could not see why and when I said I would use 1,0 my suggestion was uproarious.
I could not see why and when I said I would use 1,0 my suggestion was uproarious.
Does "uproarious" mean that it created an uproar? If so, I'm not surprised. Were those also the days of 6mm², or even 10mm², cooker circuits??
Kind Regards, John
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1.5 cable is useful if you want a dedicated socket for your fridge, or a separate circuit for your boiler. or if you want to "power" things from your lighting circuit (according to the regs a lighting circuit doesn't power things so can be <1.5mm2)
Indeed - and immersion circuits etc.. I don't think anyone has suggested otherwise.
I suspect that, under current regs, most people just apply common sense about that. However, if it remains per draft, the 18th ed. will allow 'lighting circuits to supply "associated small power-using equipment".
Kind Regards, John
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History has trained us to do things that now do not make sense, and we have that "I am sure I read some where" thing and not until we hunt do we find it's not there any more.
It seems well before I was born there were two separate supplies one for lighting and one for sockets, and lighting supplies cost less than power supplies, and it was illegal to use the lighting supply for anything other than lights.
Of course people took a chance and used the cheaper lighting power, and by time I was born the two were combined on the same meter, however my grand dads house had just two 15 amp sockets so it was common for power to be taken from the lights, the Y adaptors were common only after the war did we get the 13A socket and according to my father he was proud his new post war house 1954 had 5 sockets.
There was a concerted effort to stop people using lighting supplies for power, the Y splitters disappeared by 1966 the rules had changed and lights had earths, once lights had earths the only problem was the BA22d lamp fitting did not have an earth wire to it, and at that time the idea of class two had still not really taken off.
The BA22d plug also went as did the 2, 5, and 15 amp sockets although I am unaware of any ban as such they just were not sold any more.
We also had a couple of changes in the format of the regulations, back in the days of 13th and 14th edition there was no on site guide everything was in the regulation book, with distance of socket from a sink and other advice, by the 16th Edition we had the advice and rules put into two separate books and to allow new equipment like the waste disposal unit statement giving distance from sink where replaced with the system being appropriate for the environment.
As time has gone on it has been more and more a problem to interpret what has been written, and the on site guide is often looked at in the same way as the regulations plus the other IET publications saying how inspection and testing should be done for example.
Some times one does wonder at if it makes sense, with lighting track we had 6 Amp fuses in the plugs yet the engineer at the time still wanted the lighting splitting in a way which allowed us to use only 16A MCB's because that is what it said in the regs book, one would have considered low bay lighting was rather different to lighting in a house.
I was told for years the regulations say sockets need to be one meter from the sink, unlike when the bathroom rules changed I was likely not in the county when sink rules changed for followed the old ideas for years after it was changed.
Even BS7671 is not law, however if you don't follow it you would need a really good excuse.
It seems well before I was born there were two separate supplies one for lighting and one for sockets, and lighting supplies cost less than power supplies, and it was illegal to use the lighting supply for anything other than lights.
Of course people took a chance and used the cheaper lighting power, and by time I was born the two were combined on the same meter, however my grand dads house had just two 15 amp sockets so it was common for power to be taken from the lights, the Y adaptors were common only after the war did we get the 13A socket and according to my father he was proud his new post war house 1954 had 5 sockets.
There was a concerted effort to stop people using lighting supplies for power, the Y splitters disappeared by 1966 the rules had changed and lights had earths, once lights had earths the only problem was the BA22d lamp fitting did not have an earth wire to it, and at that time the idea of class two had still not really taken off.
The BA22d plug also went as did the 2, 5, and 15 amp sockets although I am unaware of any ban as such they just were not sold any more.
We also had a couple of changes in the format of the regulations, back in the days of 13th and 14th edition there was no on site guide everything was in the regulation book, with distance of socket from a sink and other advice, by the 16th Edition we had the advice and rules put into two separate books and to allow new equipment like the waste disposal unit statement giving distance from sink where replaced with the system being appropriate for the environment.
As time has gone on it has been more and more a problem to interpret what has been written, and the on site guide is often looked at in the same way as the regulations plus the other IET publications saying how inspection and testing should be done for example.
Some times one does wonder at if it makes sense, with lighting track we had 6 Amp fuses in the plugs yet the engineer at the time still wanted the lighting splitting in a way which allowed us to use only 16A MCB's because that is what it said in the regs book, one would have considered low bay lighting was rather different to lighting in a house.
I was told for years the regulations say sockets need to be one meter from the sink, unlike when the bathroom rules changed I was likely not in the county when sink rules changed for followed the old ideas for years after it was changed.
Even BS7671 is not law, however if you don't follow it you would need a really good excuse.
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Uproarious: provoking loud laughter.
J
jg321
BAS - did you see my question about this earlier?
I'm genuinely interested in the answer!
Jon
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