socket

[Buzz-light-bulb]

Little scenario for you all.

I've been doing an eicr today and come across a double socket wired as a radial on a 2.5mm t-e, which is protected by a 32 amp rcbo.
Technically this cannot overload as the cable can withstand 27 amp ref method c. Unless mr DIY comes along and starts adding new sockets which I am not responsible for so my question is would you leave it

 

[Colin33]

The fuses in the plug tops will stop an overload on the cable. This is no different to tapping of a busbar chamber (industrial) in smaller tails and having a switch fuse inline after a meter or 2 of cable. Protection against over load does not always have to be at the source of the circuit.

So based on this assumption I could wire a single 13A socket on the end of some 1mm cable from a 50A MCB in the CU?

 

[Pete999]

To protect our customers, as well as ourselves, we have to comply with BS 7671, the regulations for final socket circuits are there for us all to see. Should we detract from these regulations then we are in dispute with the EAW and in the eyes of the law, we are breaking this Act. If we install socket outlets in line with BS 7671 then, surely we are complying with the current regulations, until someone tells me different, then I will install 13amp socket outlets, in compliance with BS7671, 20amp radials with 2.5mm, 32 amp radials with 4mm and Ring Final circuits 32 amp with 2.5mm

 

[HappyHippyDad]

Where in the regs does it say you can wire a 2.5mm twin and earth and protect it with a 32 amp mcb you can with an additional fused spur as well as 1.5mm protective device for 2.5mm twin and earth is as stated in the little green book is 20 amp which is an A3 radial ,there is a risk of potential over load , how longs the cable length one bit of insulation will de rate the whole cable I would quite happily put it down as a C2 ,there are so many unfused 3 way adaptors out there i wouldn't risk it

Page 425, Appendix 15 Fig 15A

"An unfused spur may be connected to the origin of the circuit in the distribution board" with regard to connecting one (2.5mm) spur at the CU from the 32A MCB of the ring.

I feel like I'm arguing against the case for doing anything now! I'm not, I dont like it and I'd tell the customer so, but its not breaking the regs.

 

[Plonker 3]

Reg 434.2.1 could be applied here.

 

[NickD]

I will install 13amp socket outlets, in compliance with BS7671, 20amp radials with 2.5mm, 32 amp radials with 4mm and Ring Final circuits 32 amp with 2.5mm

Where in 7671 does it mandate that?

 

[HappyHippyDad]

So based on this assumption I could wire a single 13A socket on the end of some 1mm cable from a 50A MCB in the CU?

I think its a good idea to show extremes when getting your point across XT but... you are just looking at overcurrent with the above example not fault current, also it would be completely unrecognised by electricians and therefore far more likely to cause problems and also its against the regs, whereas one 2.5mm spur from the origin would be ok for fault current, fairly recognised and adhere to the regs.

But!! If it was just a 2.5mm coming out of a 32A MCB with no ring then why not advise the housholder to change to a 20A MCB, you dont have to but it seems like a good idea.

 

[Badged01]

So based on this assumption I could wire a single 13A socket on the end of some 1mm cable from a 50A MCB in the CU?

No, no, no! Minimum cable size for power circuit is 1.5mm but yes a single 13A socket on a 50A MCB in 1.5mm could be done. (433 & 434 give details of how & why!) Whether you'd want to do it is perhaps another thought ....

 

[HappyHippyDad]

Reg 434.2.1 could be applied here.

That is a bit contradictory to Fig 15A isn't it!! The only thing I can say to that is reg 433.2.1 doesn't have to be met if Reg 433.2.2 applies, but it doesn't look like it does!

The only other defense I can use is Fig 15A is extremely clear in its acceptance for a spur from the MCB, whereas the reg you have quoted is not as specific.

 

[7029 dave]

No, no, no! Minimum cable size for power circuit is 1.5mm but yes a single 13A socket on a 50A MCB in 1.5mm could be done. (433 & 434 give details of how & why!) Whether you'd want to do it is perhaps another thought ....

You would not be doing it in my house or any of my jobs, straight out of the door tools first.......!!

 

[Badged01]

Appendix 15 is informative and just sets out a possible option for a solution to 433 ...... there are other ways to skin the cat by careful reading and interpretation of the regs!

 

[Badged01]

You would not be doing it in my house or any of my jobs, straight out of the door tools first.......!!

And you're technical justification for that in-line with regulations would be .......

 

[Colin33]

I think its a good idea to show extremes when getting your point across XT but... you are just looking at overcurrent with the above example not fault current, also it would be completely unrecognised by electricians and therefore far more likely to cause problems and also its against the regs, whereas one 2.5mm spur from the origin would be ok for fault current, fairly recognised and adhere to the regs.

But!! If it was just a 2.5mm coming out of a 32A MCB with no ring then why not advise the housholder to change to a 20A MCB, you dont have to but it seems like a good idea.

I certainly wouldn't advocate the scenario, and have always worked on the basis of MCB egual or less than CCC of cable. I have always replaced 'offending' MCB's in the past with something more 'suitable' but maybe I've been over cautious? I don't get involved with EICR's so don't have the dilemma of which code is 'appropriate'

 

[jamie-spark]

See 433.1.103

 

[Hawkmoon]

Say it like it is Glenn

Yes, because it is total crap!! lol

 

[Hawkmoon]

Well in this case it clearly doesn't comply. does it? if we don't comply then it's the slippery slope to butchery

Explain to me where/how it does not comply...

 

[Hawkmoon]

I've always thought that the sole purpose of the Fuse/MCB was to protect the cable ie the MCB needs to be equal to or less than the maximum current carrying capacity of the cable. So in this case, the 32A MCB is not suitable.....

Overload protection does not have to be at the origin of the circuit...

 

[NickD]

Yes, because it is total crap!! lol

But with an ickle maggot of truth wiggling about in it.

 

[jaypp]

deleted.

 

[Hawkmoon]

So based on this assumption I could wire a single 13A socket on the end of some 1mm cable from a 50A MCB in the CU?

No, because even though, in your example, overload considerations may be met (though doubtful), thermal constraints (cpc fault current) certainly are not.

 

[dazza1981]

Overload protection does not have to be at the origin of the circuit...

So you think its ok to have a 1.5mm cable protected by a 50 amp breaker???

 

[7029 dave]

The op of this thread EICR different story, BUT to create a radial 2.5mm backed by 32amp mcb, come on basic electrical craft principles never mind 1.5mm, and all this talk about relying on fused appliance's to protect the CIRCUIT against overload current is crab.!!!

 

[gazj82]

No, but it is ok to have protected by a 13a plugtop fuse at the end of the circuit is as far as overload is concerned.

 

[HappyHippyDad]

I certainly wouldn't advocate the scenario, and have always worked on the basis of MCB egual or less than CCC of cable. I have always replaced 'offending' MCB's in the past with something more 'suitable' but maybe I've been over cautious? I don't get involved with EICR's so don't have the dilemma of which code is 'appropriate'

I wouldn't say that.. I'd say "sensible".

 

[Badged01]

Have a look in some industrial busbar chambers for how conductors are protected coming off the busbar against overload (and fault) ......

 

[gazj82]

Dave, you cannot load the CIRCUIT any higher than 13A, unless you are abusing the plug and socket system

 

[dazza1981]

Ok i will just use any breaker i have spare in the van for any circuit then provided its fused at the end of the circuit somewhere

 

[gazj82]

Ok i will just use any breaker i have spare in the van for any circuit then provided its fused at the end of the circuit somewhere

The cable would be protected against overload - IF

It only served one piece of equipment at the end of it's run and nothing on the way, so you can't have a radial with 3 double sockets on it obviously.

Obviously you can't have a 16A socket at the end because these have no fuse system, but you could have one 13A socket or one switch fuse (fused appropriately for the cable)


I am not saying I go out of my way to install like this, I use an appropriate sized MCB at the origin like anyone else, but technically you don't have to.

 

[Hawkmoon]

Ok i will just use any breaker i have spare in the van for any circuit then provided its fused at the end of the circuit somewhere

But then you are giving no consideration to thermal constraints...

Producing extreme and ridiculous examples does nothing to contribute to this debate...IF overload and thermal constraint limitations are met, it complies with BS7671 so no code, no comment :13:

Why do you think it is acceptable to install a 2.5 spur from an RFC?

 

[Badged01]

Ok i will just use any breaker i have spare in the van for any circuit then provided its fused at the end of the circuit somewhere

You need to be careful there or that 6A breaker you put in might keep tripping every time they put the shower on .......

 

[dazza1981]

You need to be careful there or that 6A breaker you put in might keep tripping every time they put the shower on .......

You know what i was getting at badged