Unfused spur in radial circuit from DB?

[Rampage]

Can I use an unfused spur direct from the DB on a 20A 2.5mm radial?
In the BGB it says you can on the 4mm radial but it isn't clear if you can or can't on a 2.5mm radial?!

Thanks.

 

[telectrix]

don't see why not. might be an idea to label CU as next sparks along might look at the MCB and assume its a ring final.

 

[Robinson]

CAnt see why not either. what else is on MCb? As tele said label up cu. make nice and clear.

 

[Paul.M]

I can't remember what reg it is but yes you can have a single outlet on a unfused spur fed from the mcb long as csa and fuse rating are correct. As above label the cu and no problem.

 

[Rampage]

Thanks. It's a design project so nothing is installed!
The radial just feeds around 6 sockets.
I might even turn it into a ring as there will be computers on the circuit so will will better protected from earth current if there are two CPC's.

 

[Paul.M]

1st thing to consider is the total load on the mcb for both circuits fed from the same mcb.

2nd is why would having 2 cpcs in a ring help you? It would reduce the amount of resistance returning to earth via the met depending on the location of the fault/earth leakage on the ring (shortest path to earth and all that).

 

[72-van]

This is an interesting topic .

Would i be right in saying that 6 sockets with It equipment at roughly 2.5ma earth leakage each is greater than the 10ma recommended and so warrants the use of high integrity earthing .

I hope perhaps one of our site experts comes along and gives a good write up on this

 

[Deleted member 19807]

Can I use an unfused spur direct from the DB on a 20A 2.5mm radial?
In the BGB it says you can on the 4mm radial but it isn't clear if you can or can't on a 2.5mm radial?!

Thanks.

its a standard radial, 20A mcb, 2.5mm cable, the 4mm cable in the BGB is on a 32A MCB, just mark it sockets in the cu, as long as the design load is not larger then 20A its fine as described in the op.

 

[MarkieSparkie]

This is an interesting topic .

Would i be right in saying that 6 sockets with It equipment at roughly 2.5ma earth leakage each is greater than the 10ma recommended and so warrants the use of high integrity earthing .

I hope perhaps one of our site experts comes along and gives a good write up on this

You are correct in assumption. Accumulated protective conductor current >10mA requires 'high integrity CPC' 543.7
See OSG 7.6.3 and GN1 8.1 for further information.

 

[Robinson]

1st thing to consider is the total load on the mcb for both circuits fed from the same mcb. .

exactly what i thought . surely this would be first step.......

 

[72-van]

You are correct in assumption. Accumulated protective conductor current >10mA requires 'high integrity CPC' 543.7
See OSG 7.6.3 and GN1 8.1 for further information.

I dont have either of these publications if anyone would care to give a full explaination it would be much appreciated .

 

[72-van]

Go on guys someone on heres an expert at this line .

 

[i=p/u]

any equipment having more than 3.5mA but not exceeding 10mA shall be either permenatly connected to the fixed wiring without a plug or socket outlet or connected by means of a plug and socket outlet complkying with bs en 60309-2

*over 10mA shall be connected to the wiringing of the installation, with the protective conductor in accordance with 543.7.1.3.the permanent connection to the wiring by means of a flexible cable.

* a flexible caable with plug and socket complying with 60309-2 provided that either
(a) the protective conductor of the associated flexible cable is of csa area not less than 2.5mm for plugs rated at 16A and not less than 4mm for plugs rated over 16A

(b) the protective conductor not less than that of the line conductor...

* a protective conductor complying with 543 with an earth monitoring system to bs 444 installed which, in the event of a continuity fault occuring in the protective conductor, automaticly sissconnects the supply to the equipment....

 

[72-van]

So am i reading this correctly that in our thypothetical situation with what was it six sockets full of it in a radial .That either the iec lead needs the plug cut off it and wired into a face plate type arrangement or because there are several peices of equipmnt that equpment should be fitted with the blue 16 amp type plugs.

I have often wondered about small offices clearly wired in 2.5 twin n earth with say eight or so pc's all on the same ring main .

 

[72-van]

bump

 

[Rampage]

I think so, I happen to have read up on this in the last few days.
I don't need to use a high integrity CPC connection in the end