Circuit Dilemma...

[GaryMo]

As I typed above, if you have a 15A BS3036 then you must use cable capable of carrying 15/0.725 which works out to around 20.7A. You don't mention if you have thermal insulation surrounding any cables the above is based on not.
1.5mm2 (if indeed your circuit is wired in 1.5mm2 cable) won't carry 20.7A at 30 degree's Celsius so I would suggest changing your 15A fuse to a 10A fuse (assuming no thermal insulation).
If your current loading, after applying diversity, is over 10A then you should be looking to split the circuit.

 

[essexjohn76]

As I typed above, if you have a 15A BS3036 then you must use cable capable of carrying 15/0.725 which works out to around 20.7A. You don't mention if you have thermal insulation surrounding any cables the above is based on not.

no - no thermal insulation surrounding cables

1.5mm2 (if indeed your circuit is wired in 1.5mm2 cable) won't carry 20.7A at 30 degree's Celsius so I would suggest changing your 15A fuse to a 10A fuse.

is this as simple as replacing the 15A BS3036 with a 10A one at the CU?

If your current loading, after applying diversity, is over 10A then you should be looking to split the circuit.

loading should be ok i think. currently there are 14 lights, 2 exhaust fans and 1 water scale inhibitor. when the renovation is completed there will be no more than 18 lights.

 

[GaryMo]

is this as simple as replacing the 15A BS3036 with a 10A one at the CU?

Yes, as you're downrating and not going the other way.
Don't just change the fuse wire though, try and source a 10A carrier and holder.

Thinking about it, I'm not so sure 10A BS3036 exists

If not, is you consumer unit made by Wylex? If so then you may be better with a 10A type B MCB.

 

[sparkyspike]

Identifying cable sizes isn't always easy. Best bet is to do what you've already tried and hold up a piece of 1mm and 1.5mm next to your wiring and compare. Obviously if you have 1mm cable then you'll need a 5 or 6A fuse. And smaller circuits!

 

[securespark]

Because you have rewireable fuses this means that your wiring is over 40 years old. You should consider a complete rewire.

NOT ALWAYS TRUE....

 

[Master of None]

My house was built in 1982, Wylex fuse wire type cartrages, Is this odd? now wylex cu, with dedicated freezer 16a mcb 2.5mm radial non rcd. Is this the best config.

 

[GaryMo]

So, without any other correction factors, all cabling on your lighting circuit must be capable of carrying 20.7A (15/0.725) which is greater than the current carrying capacity of 1.5mm t&e even when using reference method C (clipped direct).

And quite wrong!

Considering you were signed in and making a nuisance of yourself today I'm a little surprised you didn't take the opportunity to correct my 'mistake'.

Don't be shy!

 

[holmslaw]

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[GaryMo]

So, without any other correction factors, all cabling on your lighting circuit must be capable of carrying 20.7A (15/0.725) which is greater than the current carrying capacity of 1.5mm t&e even when using reference method C (clipped direct).

And quite wrong!

Your calculation was correct.

I know. I was refering to the installation as it is in it's present form, in other words it has been installed with an incorrect fuse rating.

As for being a nuisance, this has resulted in an answer to the op that has been an eye opener to everyone - including your self.

Not at all, I've learned nothing in this thread that I didn't already know.

 

[ban-all-sheds]

I've real respect for your in depth knowledge, but please don't turn into a bas or softus, whose intentions seem only to browbeat and attack.

If you regard telling you that you are wrong when you are, and persisting in telling you that when you persist in being wrong, as browbeating and attacking then you'd better either get used to it, or stop being wrong.

 

[Softus]

I've real respect for your in depth knowledge, but please don't turn into a bas or softus, whose intentions seem only to browbeat and attack.

My intentions are simply the pursuit of accuracy and safety.

Since you're neither accurate or safe, and since you have a long way to go before you become either, your errors will continue to be pointed out to you until you stop posting them on the forum.

 

[holmslaw]

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[holmslaw]

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[holmslaw]

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[ericmark]

Holmslaw according to BS 7671:2008 421.1 and 510.2 Manufacturers' instructions shall be complied with. Most ceiling roses are rated at 5 or 6 amp so although 559.6.1.6 says 16 amp in most cases it is 5 to 6 amp max. Not sure why 5.1.1 has been quoted as 433.1.2 does not refer to re-wireable fuses? RF Lighting is spot on with his comments. Unless there are no ceiling roses you are limited to 5 amp.
Eric