does this comply?

[ianmacd]

Here we go again. How about backing up your comments with some regs as no one that thinks it complys has yet but there are plenty that porve it doesnt (including the tech support line from the little club).

 

[Lee321]

I'd fail it if nuisance tripping was reported by the user as the circuit will have been fitted with a under size device for Ib where it gives fault protection and the spur/socket give olp by way of 433.3.1(ii)

 

[Nicky Tesla]

IAN

Doesnt have to be a ring, rings av nawt to do wiy it

"standard circuits"

 

[ianmacd]

IANDoesnt have to be a ring, rings av nawt to do wiy it

"standard circuits"

Hows it comply with 433.1.1?

 

[Adrian]

Can we have a vote on this

does it comply or not

it would be nice to see if its a 50/50 split

also who would deem this to be unsafe or just poor practise

or nothing wrong at all

I would get the voting poll going but I don't know how to (not good with stuff like that )

 

[Andy™]

make a poll

 

[ianmacd]

I assume from the lack of regs supporting its compliance that no one can back up their claims?

 

[Lee321]

I assume from the lack of regs supporting its compliance that no one can back up their claims?

like wise

 

[Badger]

[quote name='Andy

 

[Andy™]

I assume from the lack of regs supporting its compliance that no one can back up their claims?

no point.

 

[Manator]

A poll has been started, any comments about why you voted should be posted here, and not via the poll.

I have my own views about compliance on this subject that has not so far been mentioned.

 

[Lee321]

A poll has been started, any comments about why you voted should be posted here, and not via the poll.I have my own views about compliance on this subject that has not so far been mentioned.

please add your input after all this is a good discussion thread. we all learn

 

[Manator]

[quote name='Lee

 

[ADS]

I will be more than happy to do so.When you design any circuit, you will eventually have to include any alteration to that circuit, that could cause a problem.

So if we take this example, we know that whilst its two seperate 2.5mm cables and the end protection is provided by FSU, we have no control on any additions.

You could theoretically end up with two double socket outlets, or spurs off the said radials.

Good practice would prevent any designed circuit to become dangerous or unstable, so both 2.5mm could have been designed far better and still provide protection if the designer had limited its potential use.

The end result could be that a 2.5mm radial protected by a 32amp mcb, could be used to supply a full circuit it is not designed to do.

Its not what we put into the design, its what others will take out of it.

I personally would not design a circuit with two 2.5mm sharing a 32 amp mcb, regardless of how the end protection is acheived, unless I had full control over any alterations to the installation.

I do not think anyone has mentioned any additional alterations, which is what I based my initial comment on.

Hi Manator,

The exact same argument could be used against a spur off a ring final - we can't really design with a view to alterations people might make in the future

 

[Manator]

Hi Manator,The exact same argument could be used against a spur off a ring final - we can't really design with a view to alterations people might make in the future

We have to assume that any alteration from any circuit is carried out by a competant person, the example you give would counter my argument I agree.

However, as the circuit is designed as a ring, and protection has been provided for such, the limitations are negated. If you design into the circuit an absolute then you will always end up with a problem.

The end result is you have to end up with a safe and workable design, putting two radials on a 32amp mcb is, in my opinion, a bad design.

 

[ADS]

Agreed.

As I said earlier, I wouldn't do it - I can't even think of a reason for wanting to do it, but it does make an interesting debate on whether it complies with the regs.

 

[maselec]

this has nothing to do with a ring. the fact is, the cable is protected against fault current by RCBO. its protected against overload by SFCU. it does not contravene any regs. the design is fully compliant with 7671

So by this reckoning any circuit containing a socket or a spur is suitably protected against overload by fuses in the appliance plugs or FCU's?? If this was a single 2.5mm radial circuit rather than 2 would we protect it like that? because it amounts to the same thing - RCBO gives fault protection, upstream fuse gives overload protection. Don't forget that to blow that upstream fuse the overload current must first make its way through the 2.5mm to get there.

Its not just bad practice, its daft and totally unnecessary, this could easily cause problems if someone adds to or changes the installation wether it strictly complies or not, just stick them on a 20A and the jobs a good un.

 

[Riggy]

have made a poll in the poll section

I have made another poll which covers the (in my view) key piece of information from the original post that Badger's poll misses. :innocent

 

[Graham Lister]

This is in the top 12 of most viewed threads, cmon one more push as we could have a top ten here. The new poll by riggy is more in line with the situation outlined by the OP. The badly worded original poll should be discarded please admin.

 

[ianmacd]

I have made another poll which covers the (in my view) key piece of information from the original post that Badger's poll misses. :innocent

Yours misses the point too.

I do not think anyone is questioning if 13A fuse can protect a 2.5mm cable. The issue is actually that an unfused outlet for current-using equipment is not suitable for overload protection for the cable preceeding it.

The other issue is the distance from the last change in current-carrying capacity (i.e. the MCB) needs ot be within 3m too if being used as fault protection.