20A radials often use more cable when installing than a ring, offer very little in the way of diversity and require just as much (if not more) work to install than a ring.
There are times when they are useful but not very often.
Faulty radials are likely to be noticed by the householder, things like sockets that don't work. Most of the other faults can be found with a simple plug in tester from Argos.
Of course it can alter the load. There is nothing to stop it.
See above, its obvious once you realise that it can alter the load. Without a working fuse in the plug there is nothing to stop you overloading a spur. There is even an argument that it could overload the ring itself if the plug is in the "wrong" socket.
You really are as thick as Jerry. I thought this was done to death a few weeks ago.
Putting the wrong fuse or a nail in a plug top does NOT alter the load. The load will draw whatever current it draws, regardless of whether it does so through a fuse (correct or incorrect) or a nail. I am, of course, assuming that the nail and all fuses in question are rated for the normal load current.
Now, if you want to talk about what happens in the event of a fault...
MBQ
If its just using it for ignition, and displays. lights etc, then it will be a tiny load. Even a single electric oven will tend to be under
2.5kW.
And since screwed connections tend to be a failure point in circuits, why introduce more of them!
or just design them all so they are "safe" to IR test.
More to the point, modern patterns of usage[1], are also very well suited to ring circuits - so in a sense they are more rather than less appropriate now than at any time in the past.
[1] a large number of small loads scattered over a wide area, and a few larger loads that tend to be used intermittently in different places around the house. The exception to that is a kitchen, but even there assuming the layout is not unduly unbalanced, its a good way to supply a shed load of power without making the physical aspects of wiring particularly difficult.
the sentiment, a decently laid out CU isn't
You could do what Adam suggests and test LN->PE at 500V, then, just to be pedantic, test L,L,PE in all combos at 250V.
But I suspect any decent electronics will be happy at 500V DC seeing as that isn't much more than the top of the 240V sine plus a few spikes.
Part of the idea with the shorting link though, was to aid the R1+R2 (and R1+Rn) tests - means disturbing no terminals other than the CU.
Exactly my thinking.
I have one short ring[1] in the kitchen for 2 doubles and 3 fixed appliances, another lower loaded but loads-of-sockets kitchen ring that is shared with the adjacent bedroom, 3rd ring doing the other 2 bedrooms and hall and potentially a 4th upstairs (in the dormer).
[1] This ring got special attention - one end finished right next to the CU, the other end is 3m away. I actually ran both legs along the joists to the opposing external wall (ring is on the centre wall), along a bit then straight back to the CU - "wasting" about 8m cable per leg but ensuring they remain balanced.Testing with a clamp meter, each leg is balanced to about 45% vs 55% which is pretty good - I had it loaded up with *all* my oil heaters - total load 42A for 10 minutes. Cables just pereceptibly warm where they went as a pair down a short bit of 20mm conduit into the top of the CU.
Dread to think how it would have behaved if I hadn't balanced it.
Others might have called for 2x20A radials there, but the rational was the same - one radial might have had 20-ish A from a double socket plus a tumble dryer for probably long enough to trip a 20A breaker, while the other might have had a dishwasher and bugger all else. Depends on how you layout the appliances, kettle and microwave...
That is actually pretty neat.
A 33 to 67 balance/split is usually aceptable.
And the daft thing is, I believe that a 4mm 32A radial is often ideal to remove the high loads such as a washer and tumble dryer. I do not have anything against radials when used correctly. Removing the loads from a washer and drier makes the rest of the load on the kitchen ring irrelevant. A kettle is used for a few minutes at a time and so is the microwave etc. And there is no point in designing a circuit to suit the appliance layout if you are married.
You are the one being thick! What if the nail is in a fourway strip? Now go away and think about it.
With someone that doesn't even know multiway strips exist? Why bother?
Who said to use screws?
The multiway strip will melt. Just as it usually does even when protected by a 13A fuse.
That's probably the best outcome, however Murphy says the cable will melt, the PVC will emit lots of smoke killing the kids, the copper will spark and the building will burn down cremating the dead. After all they won't have a smoke alarm.
And it will have nothing to do with a correctly installed ring (including spurs) or radial circuit.
And your point about spurs from a ring was?
A radial circuit will not do that, the breaker will trip before the cable can melt as no cable is rated below the breakers rating.
A spur on a ring will be overloaded as the only thing preventing the overload on the spur is the nail in the plug (and we all know how good they are don't we?). The 2.5 mm cable is below the rating of the breaker so it can be overloaded unless the plug fuse works. I thought that was the obvious bit.
see the obvious bit above.
Would you bet your life on that? I will happily bet my life that you are wrong. You have never read BS 7671:2008 and you have never read the part on
32A radials.snipped-for-privacy@m20g2000prc.googlegroups.com...
Then you deserve all you get. You really ought to know better.
MBQ
The whole dennis line wiped out for want of a fuse...
Fingers crossed.
So what have they done wrong in designing 32A radials then?
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