Ring Main Regulations

[Chri5]

Take a picture and post it- takes all the guessing out of the post.

A fuse would normally have either one live (radial circuit- lights, cooker, maybe a 20a socket radial) or a pair which as you may know is a ring.

A ring is normal for sockets- a good installation will have at least a separate ring for each main floor- Often the kitchen has a ring on it's own- although radials seem to be making a revival.

Three lives out of one fuse could be a ring AND a radial which is naughty, more so if the fuse is 32a and the radial cable (one of the 3 lives) isn't larger than the other two. To support a 32a radial 4mm twin and earth is used- sometimes larger TE depending on the install, design, distance etc.

It could be 3 radials, say for different areas of lights- I've seen plenty of variations on the theme, but all (to my mind) slip light of good practice.

Post a picture and if you can (and it will help you / others) list out the electrical service used in the house- Lights, sockets, cooker, shower, CH etc........

Then remove each fuse one by one and see exactly what each fuse is covering. If some of your wiring seems iffy it's good to check all the rest out before calling someone in, it eliminates guess work and saves time/ cost.

Please make sure that you work safely. When taking a cover of a fuse board do switch off the full supply and remember even though it's off, there will be a live feed to the main fuse board on/off switch (unless you have further isolation via a separate switch).

Take care.

 

[ricicle]

Three lives out of one fuse could be a ring AND a radial which is naughty, more so if the fuse is 32a and the radial cable (one of the 3 lives) isn't larger than the other two.

Nothing wrong with a 2.5mm² spur (one single or one double) off the ring taken from the MCB/fuse

 

[taycast]

Thanks all for your thoughts. Will check set up and try and photograph. Will be back in touch. [/img]

 

[Chri5]

Three lives out of one fuse could be a ring AND a radial which is naughty, more so if the fuse is 32a and the radial cable (one of the 3 lives) isn't larger than the other two.

Nothing wrong with a 2.5mm² spur (one single or one double) off the ring taken from the MCB/fuse

Unless the spur is a distance away, in which case the 32a fuse is overrated for the cable size, generally 2.5 TE is rated up to 26a on a radial (isn't it) and hence why 20a fuse is normal.

Admiteddly there's few product for domestic use (other than a mig welder) that is likely to test the cable- but surely because of the design v cable it's not best practice to provide a spur from a 32a MCB / fuse on 2.5TE to a double socket?

 

[plugwash]

taking a spur from the origin of a 32 amp circuit is no better or worse than taking one from an arbitary point on a ring.

 

[taycast]

Hi,

I have finally worked out that my ring mains are connected wrongly. The live for the downstairs leaves the downstairs marked breaker, and the other downstairs ring main live is wired into the upstairs breaker ( or vice versa). This means that when I switch off one breaker the whole house remains live as it is getting fed from the other breaker. The third live is indeed a radial for my garage.

Ignoring the garage radial, Can I sort the ring mains by disconnecting all the lves ( 4 in total) from the breakers, then, by trial and error, firstly connecting 1 live to the downstiars breaker and see which circuit ( upstairs or downstairs) becomes live, then taking another live of the three remaining and sticking that into the same breaker to see if that is the second live for the downstairs. If I get it right first time, then the upstairs is the remaining 2 lives. If I am wrong, both circuits would be live, off the downstairs breaker> I would then have determined which is upstairs and downstairs, and repeat for the other 2 lives. Is there an easier way to determine which 2 are for upstairs, and which 2 are for downstairs as none are marked.

Apologies for being extraordinarily long winded. Not like me - I am usually quiet.

 

[electronicsuk]

Trial and error is NOT a good solution, as this will potentially turn the ring into a radial (although this already seems to be the case) and could overload the wiring if any power hungry appliances are in use. That's not to mention that the other end of the ring you haven't yet connected to the breaker will also become live during your testing.

Buy yourself a multimeter, then we can explain how to use it as a continuity tester for you to identify ring pairs with the power turned off.

 

[taycast]

Thanks - will do

 

[taycast]

I have now bought a multi meter. It has a big orange dial on the front which I can use to set DC V, DC mA, and AC V etc. This is what I think I have to do to check ring mains pairing:

Switch off consumer unit. Remove two lives from downstairs breaker, and two lives from upstairs breaker. Put red probe of multi meter onto one removed live and send DC current through this. Put black probe of multi meter on any other removed live until I get a reading. This will show me which live should be paired with which. I then put each pair back into breaker, switch power on and test. If upstairs pair is in downstairs breaker or vice versa, I need to switch off power and swap pairs over, or even just swap the stickers over on the breakers>

Does this sound right? What level of dc do I set my meter at? Do I use DC V or DC mA? It also has an ohms setting? Do I need to use this?

Once again, your advice would be appreciated.

[/quote]

 

[GaryMo]

Three lives out of one fuse could be a ring AND a radial which is naughty, more so if the fuse is 32a and the radial cable (one of the 3 lives) isn't larger than the other two.

Nothing wrong with a 2.5mm² spur (one single or one double) off the ring taken from the MCB/fuse

Unless the spur is a distance away, in which case the 32a fuse is overrated for the cable size, generally 2.5 TE is rated up to 26a on a radial (isn't it) and hence why 20a fuse is normal.

Admiteddly there's few product for domestic use (other than a mig welder) that is likely to test the cable- but surely because of the design v cable it's not best practice to provide a spur from a 32a MCB / fuse on 2.5TE to a double socket?

Distance has nothing to do with current carrying capacity, only volt-drop.
Again, nothing wrong at all with a 32A OPD feeding a ring final and a spur, even if the spur is wired in 2.5mm2.
A compliant 32A ring final (including spurs) should be comprised of cables with a minimum current carrying capacity of 20A.


Taycast, you need to use the resistance setting, marked with a Ohm symbol. There's also more to verifying a correctly wired ring final than end to end resistance measurement.

 

[leeco]

to do a continuity test you need to set your tester to 200mA and 420DC
then 1st messure between L - L , N - N, E - E,
then conect L1 to N2 and L2 to N1 and test at each socket in the ring your testing what ever reading in ohms you got on the 1st test you should get a 1/4 of the reading at each socket

 

[GaryMo]

1/4 of what? 1/4 of the line and neutral loop combined (r1+rn)/4

What about R1+R2? (r1+r2)/4

 

[leeco]

yes sorry a 1/4 of L1 - N2

 

[GaryMo]

yes sorry a 1/4 of L1 - N2

No, a quarter of r1+rn (line loop and neutral loop)

 

[taycast]

Thanks again. I think it sounds too challenging for me.....appreciate all your input. I will need to get a professional in to take a look.