Because 20A is f*ck all use to me.
I do not want to be thinking - are these sockets on the same 20A circuit
- damn I cannot plug this 3kW appliance in because there are already two high load appliances on that circuit.
I already also have enough RCBOs in my CU - I don't have space for even more, let alone the expense.
Bugger the OSG, it is a guide only. I think you WILL find them in Appendix 15 of the 17th.
4mm doesn't cut it for Reference Method B (a common installation method in my house).
Bollocks. Have you ever done any testing and inspection work?
Inspections will disturb the accessory, so you do that first[1].
The testing requires disturbing the connections at the CU only and the first test you do is an end-end test on all 3conductors which will pick up this problem. In fact that is the one test you could validly do with any old cheap multimeter or even a bulb and battery.
The next test is the 500V inter-conductor insulation test.
Once those have passed, you now know that the ring is continuous and has no single wiring error (though it may have multiple erros that cancel.
The 3rd set of figure-8 tests prove the absence of any wiring error or open circuit fault and demonstrate the soundness of the circuit both under load and fault conditions for all bar the most obscure and unlikely problem scenarios.
As long as you can reinsert the wires into the CU correctly you are good. I add an extra test of my own which is to do a few live loop impedance tests afterwards which would pick up any issues there.
[1] As we are talking about socket circuits. Lighting circuits are more of a PITA as you need to bridge out any electronic devices which unfortunately means fiddling with the accessories after the tests are done.
Pages 49 and 158 to name two references to 32A radials in the OSG.
No, I believe that the compromise is very good and we have a good safe system.
I am not sure what you mean. All circuits have breakers designed to match the cable.
Maybe, it is suggested everytime there is an update to the regs.
Yes, the rest of the circuit is 6mm T+E, from CU to cooker switch (inc socket) to cooker outlet. It's only the last jump from cooker outlet to adjacent single socket that's 2.5mm.
IIRC the cooker claims to be 13A but instructs use of heat resistant
2.5mm cable into a cooker outlet, not a 13A plug. So I've followed those instructions.Cheers, David.
No, see my reply to John: the rest of the circuit is 6mm T+E, and the cooker will be run from a cooker outlet, not the socket.
Cheers, David.
13A plugtops do have quite low specified limits on operating temperature. Whilst it won't be a problem for a gas cooker that only draws power for a light, spark and maybe a low powered warming cupboard, it might be anticipated to be an issue for a cooker that actually draws 3kW (eg dual fuel with a lumpy electric oven).
But you need to do that if you want to plug them into one end of a 2.5 mm ring, even more so with three appliances. It causes imbalance currents in the ring that can take them out of spec. Its why fixed heating shouldn't go on a ring, they don't like high load stuff at one end.
every time you disconnect the wire and reconnect it you work harden the copper and make it more likely to fail due to passing traffic, etc. If the consumer unit was correctly designed it would have test links so you could do the tests without disconnecting the wires. But why do things right when you can do them cheap?
That would be because a lot of engineers don't think rings are safe.
Queue :::Jerry:::
MBQ
And Dennis.
Whilst I don't disagree with the sentiment, a decently laid out CU isn't too bad - and your idea would require at least 3 terminals per current terminal (L,N and PE) all with per terminal links and test points - so that's 9 links and test points per device.
I wish that all dimmers came with a small shorting plug though, that could be inserted from the back of the device - that would save some faffing.
But 60 years of history prove them wrong.
Are you going to clarify what you meant by
"That would be why they added radials with breakers that actually match the cables because they didn't need to."
It doesn't actually significantly change the level of protection if you fit a full power cooker. It does change the possibility of tripping the circuit as it allows more current to be drawn. However it is still safe (well as safe as a spur on a ring) as there is no way to overload it that won't trip the circuit.
You will trip the plug fuse if you overload the socket whatever cooker you have and trip the MCB if you overload the total circuit. The same is true for if you fit a double socket but I wouldn't put a double on a 2.5 mm spur in a kitchen, someone is bound to plug in a big tea urn and a combo microwave and overload it for a couple of hours. That's what Murphy told me.
There is quite a lot of difference between it being safe and it being user friendly, you don't want circuits to trip frequently to maintain safety.
You don't think...
MBQ
Well they certainly don't......
Less if its not a ring though.
You should invent one.. a crimp on termination pin for each wire with a suitable socket should do it.
How does it? Nobody knows how many faulty rings there are as the householder doesn't know and very few are ever checked. There could be 10 there could be 100,000, until people get hurt no one cares.
It is illogical to rely on downstream breakers to protect up stream cables. It makes modification to the circuit potentially dangerous.
People do modify the circuits by putting the wrong fuse in plugs (including nails) rendering them useless for protecting the upstream circuit against overload. There was even a large batch of "genuine" fuses for plugs that didn't protect the circuit a few decades back. These led to certification being required to show batch testing had been done. God knows how many of these faulty fuses are still out there. Do you check the plug fuse for certification when you come across one?
Ditto for faulty radials.
Only if you do not know what you are doing.
Non of which alters the load on the spur or makes any difference at all to a fault current on the spur.
And the relevance to spurs and radials is?
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