Radial Circuits

Page 1 of 2  
Hi!
Upstairs, we seem to have a radial circuit.
It is protected with a 20A MCB and uses 2.5 cable.
Is there any problem with simply adding another socket on the end of it?
Sparks...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No, provided it won't be extending the floor area covered by the sockets. You can spur off the circuit wherever it is convenient, not just at the end of a long snake of sockets. However, practical considerations make it difficult to spur off a socket that already has 3 cables.
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ok, thanks!
I take it you can't subsequently spur off a mid-point spur?
Sparks...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Spur to your heart's content, provided the conductors will fit in the holes. Stick in junction boxes if you like, or don't, it's entirely up to you.
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So I can just slap a junction box in at any point and connect another 10,000 sockets (hypothetically!)
Sparks...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes*, but you are limited in the floor area that you serve. The justification is that they would prefer you to have lots of sockets so that your computer/TV/DVD etc. can have a proper safe socket instead of being plugging into an adapter. However, the floor space requirement means that you are unlikely to plug in multiple fan heaters into the circuit when the boiler goes Pete Tong.
Obviously, these maximum area rules apply only when predicted loads don't override the requirement. There's no use saying that a 20A radial is fine for a large kitchen, because it is obvious that there will be a washing machine/tumble dryer/dishwasher/microwave/kettle/iron/dual fuel cooker etc.
Christian.
* Well, actually no.
If 20m2 is allowed for this radial (as the other poster suggested, but I can't remember the figure myself), then assuming a 5m x 4m x 2.4m room, and allowing approximately 20cm x 10cm for the box, you can only fit around 2200 double sockets on the wallspace. Even a few stud partitions and ceiling mounting will be unable to fit 10,000 sockets.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I think it might be 50m2, come to think of it. 20m2 sounds too small to me.
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 29 Jan 2004 17:25:03 -0000, "Christian McArdle"

20m2 with 2.5mm cable on a 20A MCB
SJW A.C.S. Ltd.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
A quick browse on the Internet shows that your figures:

And the alternative figures:
30/32A MCB ring = 100m2 30/32A MCB radial = 75m2 20A MCB radial = 50m2
abound in equal measure. I suspect there has been a change. I wonder which is the more recent?
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 29 Jan 2004 17:46:23 -0000, "Christian McArdle"

keep 2.5mm radials on a 16A, 4mm radials on a 20A. At a push I'll put a 20A radial in 2.5mm if it's just feeding a couple of sockets. I would have to go and dig the regs out to see what it actually is but as I am always under with radials I don't concern myself too much, looking on the interweb the majority go with my way, but whether that is the most current I don't know.
SJW A.C.S. Ltd.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
"Christian McArdle" wrote in message

The larger areas (50 & 75m^2) are the more recent. The change was made in 1998, when the yellow cover OSG was published.
Reminders:
- these figures are guidance, not regulations, and must be used with knowledge of the loads likely to be connected;
- sticking to these figures does not exempt you from the need to check compliance for voltage drop, cable ratings (installation conditions, ambient temperature & grouping factors) and earth fault loop impedance.
--
Andy



Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Ring circuit 32A 2.5sq mm 100 sq meters Radial 20A 2.5sq mm 50 sq metres Radial 32A 4.9sq mm 75 sq metres
--
Chris Green

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 29 Jan 2004 20:40:31 GMT, snipped-for-privacy@isbd.co.uk wrote:

heaters. As I said I know I'm always well in. Go on then, we'll use your measurements\ratings.
SJW A.C.S. Ltd.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Any topology you like.

.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

On a radial circuit, you can spur off a spur off a spur as often as you like.
--
Andrew Gabriel

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Fused spurs are unlimited but as far as i am aware non fused spurs for radial and rings should not exceed number of switched outlets on the cct. And I would say the OP is not spurring off but extending the circuit
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This rule of thumb only applied to rings, not radials. It has now been reworded that the likely current draw of the circuit should be ascertained to ensure that similar currents flow in both legs. (i.e. you shouldn't put all the spurs and high current devices on one side of the ring). The spur rule was designed to help do this, but was not very effective.
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I can see your point on load sharing and as you said have as many outlets as you like as long as protection is ok but still cant find it in OSG , but i will not lose any sleep over it !
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's in the Appendix on 'conventional circuits for BS1363 (?) sockets'.
--
Chris Green

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

is more than likely to be fine, assuming you are in an average sized house that is. Are you putting the socket in another area or in a room already covered by the existing circuit? Reason being a radial should not cover a floor area of more than 20sqm if it is on a 20A MCB in 2.5mm cable.
SJW A.C.S. Ltd.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.