4mm radial circuit

[Sparkytlec]

I usually use 4mm radials for socket but put them on a 20A o/c device and 2.5mm on a 16A. I haven't had a report of them tripping on overload either. It's very unusual for me to use a ring circuit these days to.

 

[marshr02]

I usually use 4mm radials for socket but put them on a 20A o/c device and 2.5mm on a 16A. I haven't had a report of them tripping on overload either. It's very unusual for me to use a ring circuit these days to.

Thanks for reply. Out of interest if you are using a 20A o/c device, why do you run 4.0mm. Is it due to volt drop or sim - as obviously 2.5mm carries 20A on most installation methods...? Cheers

 

[marshr02]

I thought about using a 4mm 32A radial once and came to the same conclusion as you. It only seems to be good for ref method C and I think there could be a problem fitting three 4mm conductors into accessories if you need to branch off at any point or modify the circuit at a later date, so I used a 2.5mm ring instead.

Thanks for reply. I suspect that it would be useful for the IET or similar to perform tests with T/E in installation method B, rather than using the multicore values in BS7671. I suspect the cable is JUST OKAY for 32A - although because it's on the limit I would use it sparingly when layout makes radial more suited in the kitchen. We really could do with one of the professional bodies carrying out the test and issuing a judgement - rather than loads of us wasting time/sleep wondering if we should downrate the CB. Cheers.

 

[Sparkytlec]

Volt drop is one reason in larger cable runs. But I do it that way as it gives me the option to use the o/c to follow the letter of the regs if required, but for my own piece of mind I drop to 20A

 

[Engineer54]

Thanks for reply. I suspect that it would be useful for the IET or similar to perform tests with T/E in installation method B, rather than using the multicore values in BS7671. I suspect the cable is JUST OKAY for 32A - although because it's on the limit I would use it sparingly when layout makes radial more suited in the kitchen. We really could do with one of the professional bodies carrying out the test and issuing a judgement - rather than loads of us wasting time/sleep wondering if we should downrate the CB. Cheers.

Perhaps if you disregarded BS 7671 when it comes to CCC of cables, and use the manufacturers data, you may find that your worries are totally unfounded!!

Why do you and it seems many others, need every situation documented in BS7671 (or by other bodies), it's never going to happen!! BS7671 is basically only a guide at the end of the day, your still expected to make your own educated decisions based on your electrical knowledge etc!!

 

[marshr02]

Perhaps if you disregarded BS 7671 when it comes to CCC of cables, and use the manufacturers data, you may find that your worries are totally unfounded!!

Why do you and it seems many others, need every situation documented in BS7671 (or by other bodies), it's never going to happen!! BS7671 is basically only a guide at the end of the day, your still expected to make your own educated decisions based on your electrical knowledge etc!!

Alright - easy boy.... Thanks for the reply. Purchase my T&E cables over the trade counter - no idea the manufacturer - but will look for any clue - of course I still may have a mix of manufacturers? I will look do some digging for manufacturers info on T&E though - looks interesting - thanks for prodding me in a different direction. Regarding looking to fall back on BS7671 - well the BS regs are a standard - and so if a cable is to say BS6004 then you should expect a certain minimum performance. Any Professional Engineer will tell you that you avoid designing to bespoke products IF possible - a generalised design giving more options at procurement. In this case what I NEED from BS7671 is accurate data on cable performance - to be able to make an informed decision.

 

[Heisenberg]

Perhaps if you disregarded BS 7671 when it comes to CCC of cables, and use the manufacturers data, you may find that your worries are totally unfounded!!

That's a nice try, but aside from the fact that most times data is not available for the cheaper end of the market, even a company like Prysmian only gives CCC based on 2 reference methods. Of which 'B' ain't one of 'em.

And just maybe, people are afraid to step too far from the confines and protection of BS7671 because they know that these days people are quick to sue when things go south. Not everyone has decades of experience to fall back on, so whilst what you said might apply to some, to expect it to be applicable to everyone is unrealistic.

Cheers

 

[Geoffsd]

This is all assuming that 'under the floorboards' is method B.

What does 1.5De ≤ V < 50De mean?

where De is diameter of cable and V is height of space.

I can understand one side or the other but together it doesn't seem to make sense.

 

[Guest55]

Yeah, why didn't I think of that, read replies that had not yet been written :dizzy2:

You should be a politician, answering one question with one of your own. LOL

they were written by the time you read my reply so what difference does it make ?
i should have been a lawyer with my expert arse covering posts.

 

[telectrix]

from troll to lawyer requires at least a 6 day short course. day 1. learning to lie. day 2. learning legal gobbledegook. day 3. learning to lie convincingly. day 4. learning how to backstab. day 5. review of lying abilities. day 6. award of liars (lawyers certificate).

 

[Guest55]

at the end of the day you can talk about the finer points of reference methods and ccc till the cows come home.
but 4mm under floors on a 32mcb works just fine , end of.
you either see that through experience or you get hung up on the regs because you lack said experience.
im happy to rely on my own engineering judgements that come with 20 years in the game , many others dont.

 

[Heisenberg]

at the end of the day you can talk about the finer points of reference methods and ccc till the cows come home.
but 4mm under floors on a 32mcb works just fine , end of.
you either see that through experience or you get hung up on the regs because you lack said experience.
im happy to rely on my own engineering judgements that come with 20 years in the game , many others dont.

The trouble is, a lot of you old timers want to have your cake and eat it. Anyone who comes on here and says something that is against the regs, generally but not always, gets blasted and labelled a Electrical Trainee. Yet, when the forum Illuminati do it, we're just told to accept it as 'experience'.

At the end of the day, to coin your phrase, sticking to the regs never got anyone killed, so I find it strange that people would get criticised for doing so.

Cheers

 

[Sparkytlec]

Perhaps if you disregarded BS 7671 when it comes to CCC of cables, and use the manufacturers data, you may find that your worries are totally unfounded!!

Why do you and it seems many others, need every situation documented in BS7671 (or by other bodies), it's never going to happen!! BS7671 is basically only a guide at the end of the day, your still expected to make your own educated decisions based on your electrical knowledge etc!!

I actually agree with your statement as you could wire a house in two bits of wet string if it worked. However in this day and age of litigation it only takes the slightest thing to happen and someone gets hurt, (it may not be even anything to do with the circuit you have wired) then there is an investigation and the HSE say prove your work is safe and there are only two ways to do that one is to have proven manufactures test data or to have abided with current BS7671. When you can't prove that say sorry but that's not good enough. At best it's a heavy fine at worst it's a prison sentence and yes that can and dose happen!

There fore I'm not willing to risk it.

 

[Richard Burns]

This is all assuming that 'under the floorboards' is method B.

What does 1.5De ≤ V < 50De mean?

where De is diameter of cable and V is height of space.

I can understand one side or the other but together it doesn't seem to make sense.

If say the cable is 4 mm2 flex of diameter 11.6 mm
the minimum dimension of the space must be greater than 1.5 x 11.6 mm = 17.4 mm
the minimum dimension of the space must be less than than 50 x 11.6 mm = 580 mm
Outside of these values the installation method does not apply.
Since most spaces between floor boards are greater than 17 mm and less than 580 mm it probably does apply in this case.

 

[Guest55]

The trouble is, a lot of you old timers want to have your cake and eat it. Anyone who comes on here and says something that is against the regs, generally but not always, gets blasted and labelled a Electrical Trainee. Yet, when the forum Illuminati do it, we're just told to accept it as 'experience'.

At the end of the day, to coin your phrase, sticking to the regs never got anyone killed, so I find it strange that people would get criticised for doing so.

Cheers

i've never said any of things so you must be mistaking me for someone else.
if fact im happy to admit to bending guidelines when i know an install will work perfectly fine.
i care not if others do also , thats their business.

and i'm only 41.
;-)