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.

 

[Darkwood]

You now have the consideration that one of the lights is in a bathroom and there has been no mention of 30mA RCD protection (701.411.3.3).

Aye stop that .. its an old install we are not trying to make it comply to the 17th merely answer a theoretical query that in the real world you wouldn't do for various reasons but not necessary due to regulation.

 

[Richard Burns]

We have that we cannot use 30A fuse wire from 559.6.1.6
We have 433.3.1.ii that says that because five lights is a fixed load and unable to overload that the circuit only need to be protected against fault current.
The PFC is assumed to be low enough that the 15A fuse is not unable to cope (since the 5A would have been compliant). Though calculation could be done for 534.5.2.
We do not want it to comply to 17th edition, just be safe for continued use so RCD protection is not installed.

Fit and forget!
Oh yes but as DS says I would not do this in a domestic property unless they were desperate.
I have now got another desperation to go to, so signing off.

 

[NickD]

Aye stop that .. its an old install we are not trying to make it comply to the 17th merely answer a theoretical query that in the real world you wouldn't do for various reasons but not necessary due to regulation.

But if we're talking strict compliance to the regs here for theoretical purposes, you are proposing changing the OCPD for the circuit, which means you're 'taking responsibility' for the whole circuit, hence, RCD.

 

[MDJ]

Hey up Nicks on the case

 

[Darkwood]

RB pretty much wraps it up here ... totally compliant but not a practice to condone as the domestic realm is often subject to abuse and although future changes has no implication of what you did and would be down to their own responsibility it is often practiced in domestic for these reasons to provide O/L protects beyond requirements.... only a few circuits do require OL protection namely with socket outlets on them but the rest can fall under the same omit that my example uses.

I often use this OL regulation when wiring large machines to keep cable cost down but still be within regulation ... domestic it is often unrecognised that it is an option and yes i have used it to upgrade a shower without ripping out all the existing wire for no reason.

 

[GLENNSPARK]

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

wrong.

1.5/1.0 flat twin method C is good for 19A....so a 15A BS3036 wouldn`t comply....would it.

OK correction:

20A

still doesn`t comply...

 

[Darkwood]

But if we're talking strict compliance to the regs here for theoretical purposes, you are proposing changing the OCPD for the circuit, which means you're 'taking responsibility' for the whole circuit, hence, RCD.

Valid point hence I tried to express it as just theoretical without stepping into other separate issues ... ok then rephrase the question that you came across a lighting circuit existing with a 15 fuse wire - can you change it for another 15amp wire leave it and comply with regs ... no alteration or upgrade has been made.

 

[Badged01]

Ive come in at the tail end after all the juicy bits have been aired ....... is the voltage drop compliant

 

[Darkwood]

Ive come in at the tail end after all the juicy bits have been aired ....... is the voltage drop compliant

Was just bored badge and passing time ...its a small house with 5 lights ..ill let you work out if VD is a worry or not without further info'

 

[GLENNSPARK]

Valid point hence I tried to express it as just theoretical without stepping into other separate issues ... ok then rephrase the question that you came across a lighting circuit existing with a 15 fuse wire - can you change it for another 15amp wire leave it and comply with regs ... no alteration or upgrade has been made.

its the corredtion factor to be applied for BS3036s

.725

so 1.5/1.0 good for 20A

20 X .725 = 14.5A

so its a non-conformance....simple as...

 

[spark 68]

Ive come in at the tail end after all the juicy bits have been aired ....... is the voltage drop compliant

Ha! was thinking that earlier too, I haven't looked through the regs books, I dismissed it though because our design current is fixed by the existing fixed load rather than the rating of the OCPD.

 

[shanky887614]

Various points to look at here....

Mr Burns saw the fact that id specified incandescent lamps and your typical lamp in domestic of this nature will be subject to regulation 559.6.1.6 so a 30amp wire is out of the window and won't comply.

Thus we drop down to 15amp with the same question ...

Note rating of switches etc are only subject to the load they are switching and not the fuse that covers them or we would have a lot of non compliant installs out there.

Install is your basic drilled through joists buried in plaster and insulation in loft - just to clarify although it changes little.

Nick your last sentence is key to part of it...

and there is nothing to stop someone adding a ton more light fittings, so it doesn't comply....?

I use a lightswitch to isolate the mains

of course it can be used for load

 

[Darkwood]

its the corredtion factor to be applied for BS3036s

.725

so 1.5/1.0 good for 20A

20 X .725 = 14.5A

so its a non-conformance....simple as...

Incorrect .....Calcs above ok but im using the 433.3 as we can tot up all the lamps and get a fixed load value ... the circuit cannot overload due to the nature of the loads on it so you can be cheeky and apply the regulation ... although it not common practice in domestic which i think is a good thing.

 

[GLENNSPARK]

Incorrect .....Calcs above ok but im using the 433.3 as we can tot up all the lamps and get a fixed load value ... the circuit cannot overload due to the nature of the loads on it so you can be cheeky and apply the regulation ... although it not common practice in domestic which i think is a good thing.

hmm..
OK Dark...i can live with that....lol..

 

[Badged01]

5 bulbs @ 100W say 2.5A for cash. Over a 200m radial run wired in 1.5mm T&E to method 100 --- VD = 16mV/A/m ~ 8V ( should be 7V)

So there, forget all this fannying around with overload characteristics, short circuit dilemas and adiabatic calcuations it all boils down to knowing your voltage drops.

Its non-compliant end of ......