Does this comply.... thinker of the day!

[Darkwood]

Im bored so I thought Id get your heads thinking and take note who's posting this so Im not after a straight answer yes or no! Back your comments up please with regulations.

I have a small house and they complain when a lamp blows the bs3036 5amp wire blows and they have to replace it (nuisance tripping/blowing), the lighting is on 1 circuit and covers 5 fittings - kitchen, room, stairwell, bathroom and bedroom.. they are adamant to keep using their stock of filament lamps so for the sake of this debate we are not replacing the style of lighting nor upgrading the board or fuses...

Can i fit a 15amp or 30amp fuse wire in the lighting fuse carrier noting that under the circumstances the Zs is still in compliance and still be within BS7671 and not breaching any regs.

Remember alternative solution are off the table this is theoretical to test your understanding of the regs.

 

[SJD]

What size cable is the lighting wired in, and what reference method?

 

[Richard Burns]

Hmm I would say that without any reference that you would not be able to get a fully compliant system there.
The 30A fuse wire is out because the maximum for ES/BC is 16A.
I will leave it at that for the moment.

 

[NickD]

Just for clarity, you are asking if you can put 15A / 30A fuse wire in the existing carrier? You're not asking if you can change the carrier and if necessary the receptacle to a 15A / 30A rated/labelled one?

 

[Darkwood]

To rid the idea the carrier will be undersized which isn't the aim of my question you can exchange the carrier to meet the rating of the fuse wire but this wouldn't be an issue either way tbh.

 

[NickD]

OK, I was just thinking if you put 15A / 30A fuse wire in a carrier probably labelled and colour-dotted for 5A, you'd probably get off with crucifixion. For a first offence, anyway. The switches are, surprisingly, rated to 15A / 30A I take it?

 

[Darkwood]

The rating of the accessories and carriers is irrelevant as will be made clear later...

Ill drop in a key point that has not been asked .. the lighting is the original cable which is tested fine and is 1mm t&e.

 

[nickblake]

this all depends on a few factors cable size factors installation methods etc now if its a 1.5mm cable clipped direct maximum cable rating is 20 amps so 15amps mmm looks ok but there is the correction factor for bs3036 fuse of 0.725 so if you take it with out any other factors it would be 15 / .725 = 20.69 so over the maximum rated now if you add say 3 cables you have a grouping factor of 0.70 that would then become 15/.70 x .725 = 29.42 so my answer would be no

 

[Richard Burns]

Without going too far into it to have a lighting circuit as you describe, assuming it was correctly wired at the time of installation, and making an alteration by changing the rating of a BS3036 fuse to 15A you would not be able to comply fully with the 17th edition of the wiring regulations (as amended).
There are considerations of full compliance and partial compliance and also considerations of what is excepted and what is permitted.
I am also not certain that this would definitely resolve the problem, although it should alleviate it to a very large extent.
I will put a reg number in for the 30A fuse wire as 559.6.1.6.

 

[Redvanman]

I could have misunderstood but here goes.
if you have fully tested circuit and Zs is under the new rated fuse, the earth arrangement ok, the switches and light fittings rated to the new fuse rating then I'd say you could possibly do it with a note on the board explaining what you've done as the circuit wouldn't pull more than the cable rating
but personnally I won't but it's abit like a bussbar arrangement
Have I got what your on about?

 

[Richard Burns]

For fault current on a 15A BS3036 I calculate the csa for adiabatic compliance would be ~0.5mm² or less, so that would be covered (543.1.3)

 

[Octopus]

What cu is it? Could you try a 10a mcb?

 

[spark 68]

this all depends on a few factors cable size factors installation methods etc now if its a 1.5mm cable clipped direct maximum cable rating is 20 amps so 15amps mmm looks ok but there is the correction factor for bs3036 fuse of 0.725 so if you take it with out any other factors it would be 15 / .725 = 20.69 so over the maximum rated now if you add say 3 cables you have a grouping factor of 0.70 that would then become 15/.70 x .725 = 29.42 so my answer would be no

Knowing DWs 'penchant' (lol) for overload protection may be omitted due to the nature of the load, I would say that 15A would be permitted due, as RB pointed out earlier, 16A being the max for BC/ES fittings, provided the Zs complied of course.
I would have to look deeper though to give a definitive answer.

 

[Darkwood]

Hmm I would say that without any reference that you would not be able to get a fully compliant system there.
The 30A fuse wire is out because the maximum for ES/BC is 16A.
I will leave it at that for the moment.

First point to Mr Burns - now lets just say then following this reg' (559.6.1.6) you derated the 30amp to 15amp would we now comply...

As said in the OP Murdoch - all alternatives for the theoretical point of the question are off the table.

 

[Richard Burns]

OK next consideration which I think is outside of what you are meaning since spark 68 has gone for 433.3.1 (ii), is later modification to the regs that make the existing circuit non compliant anyway, but I may not have been told about other protective devices!