Ring or Radial????

[pen_fold]

My question is:

How do I tell what type of circuit I have in my house, either ring or radial????

Moved into a our new house about a year ago (built in 1975, if that helps???). Don't know a great deal about electrics, but I want to see about taking a spur from a socket in the bedroom, but reading other posts you cannot take a spur from a socket on a radial circuit or something like that if it alters the original circuit?!?!?!

Can anyone help?

 

[Qedelec]

A ring will have two cables at the Consumer Unit.
No easy way to find out other than test the circuit when 'Dead'.
1. Disconnect supply and test its dead.
2. Prove tester.
3. Confirm cicuit is dead again.
4. Remove socket front plate and disconnect cables from accessory.
5. Measure resistance of Phase, Netral and CPC ring
Phase and Neutral should be very close in value and CPC sould be 1.67 times higher for 2.5mm T&E
This is by no means conclusive but will give you a start.

 

[securespark]

Easier to test when live, make sure you have indication of live sitn, then lock off and test again, no?

 

[comms]

A radial could have two cables at the cu.

 

[Jim2287]

if there is 2 cables in one breaker ... then just get a continuity meter on both the lives ... if there is continuity its a ring, no continuity is 2 radials

only try this when you have switched off the board at main breaker or if your supply has an isolator


the size of the breaker/fuse "may give an indication" of what you have also, if its a 20 amp then it most probably is a radial (unless the cable looks bigger than 2.5mm2)

its ok to spur off a ring or a radiall .. use a fused connection unit and the same size cable as the circuit you are spuring off of,
--this will protect the cable from overload and means if someone else spurs off of your spur then its less dangerous (if you sell your house in future)

 

[securespark]

if there is 2 cables in one breaker ... then just get a continuity meter on both the lives ... if there is continuity its a ring, no continuity is 2 radials

Not quite as simple as this.. it could be a broken ring (I have come across many). Equally, I have seen two radials that have been linked (Not so common).

the size of the breaker/fuse "may give an indication" of what you have also, if its a 20 amp then it most probably is a radial (unless the cable looks bigger than 2.5mm2)

The key word here is "may". I have seen 16A radials 20A radials, 32A radials (all in 2,5). And for that matter, the same protective devices on ring circuits.
I have seen lighting circuits in all sizes too, and even one with a 5A fuse carrier with 30A wire in....

its ok to spur off a ring or a radiall ..

yes, fine in the case of a radial, you don't need an FCU. In the case of a ring, you can only connect one outlet to a spur. If you want more, you can put an FCU on the end of the spur cable, and feed what you like off that, providing the cable is suited to the fuse size, as it is all protected by the FCU fuse.

 

[pen_fold]

Thanks for all the info.

Taking what Jim2287 said that you can spur from a radial or a ring, by using an fcu and the same size cable, here is what I am hoping to do:

1. Take a 2.5mm spur from an existing double socket, that I have checked and I think its on a radial circuit (no continuity when I did the test), I know a couple of you have said its not as simple as that!

2. At the end of the spur, I will put an RCD protected FCU (13A), as the shower pump instructions recommends it has RCD protection

3. Then, as per manufacturers instructions for the RCD, as the spur is supplying a fixed appliance, I will need to add a normal switched FCU (3A) which will have the shower pump wired into it.

Does this sound ok?

 

[Jim2287]

since you think its a radial, what Amp rating is the breaker protecting the circuit ?

 

[pen_fold]

I have just checked, the sockets upstairs and downstairs are all on the same fuse which is a 30A (old style rewirable fuse).

Would this effect what I am proposing to do??

 

[RF Lighting]

It sounds like you probably have a ring circuit in your house. If this is the case and providing you are only spurring ONE socket from the existing point in your bedroom there should be no problems.

Rob

 

[pen_fold]

Thanks!