I would expect 30mA (i.e. for shock protection rather than infrastructure / fire protection).
However "all RCBO" installs are much more cost viable these days, and even if just using the normal 17th style CU you would normally ensure the power circuits in a given place are on the "other" RCD to the one doing the lights.
There's two overlapping requirements covering this.
You need to have a fused connection where cable sizes change, and a circuit has to be fused to protect the smallest cable in the circuit. So, if your whole circuit is fused to protect 1mm cable I would accept a larger cable as a main feed to 1mm spurs. I have done this where I typically have a larger cable running from the consumer unit to a convient breakout point, where 1.5mm cable goes off to individual lighting circuits.
I've used fuse-at-cable-change typically when spuring from a 32A ring to provide a loft light where the lighting circuits are inaccessible or there's a need to have a non-lighting light so you can see when the lighting circuit is switched off. Similarly, I make sure there's an upstairs socket within extension lead reach of downstairs and vice versa.
jgh
But what defines "good quality" for crimps? I've used similar looking crimps to these
When I moved into my present house, the vendors had taken all the fancy brass sockets and switches (it was a while ago) and put back the original 1976 white contract stuff.
But they had managed to snap the 1mm cpc in two of the sockets, which were on a single ring (house less than 100 sq m), and badly connected the live to a third, so that it had no cpc at all and the ring was actually two spurs running from a 30 amp wylex rewireable fuse.
They also fitted a new kitchen and drilled right through the cooker live wire, and then repaired it with a bit of choc block which was hidden behind a fitted cabinet. I noticed the burn mark above the fuse wire carrier, that had actually melted part of the metalwork but it was 13 year before I removed the kitchen cabinet and found the 'repair'.
Quite - I've seen some real rubbish on sale. Very thin metalwork. Which simply can't grip as hard as thicker.
I only buy from TLC these days. But haven't bought any recently.
My hatred is based on their use in cars. They always give trouble - eventually. And houses tend to have a rather longer life...
But encounter fewer pot-holes ...
Generally if having made a crimp, you can't pull the wire out then its a good one... the crimp should grip hard enough to deform the wire a little, forming a "gas tight" connection.
Are you sure its the crimped bit that causes problems and not the connector bit they attach?
And don't make the mistake of thinking a ratcheting tool is always going to make a good joint as an incorrectly adjusted one just makes a lot of bad joints one after another.
It should. Now do a trial one using some scrap cable and cut off the insulation. It will not be in contact all the way round the conductor, in most cases.
Remember seeing a U-tube where various makes were run up to the full rating of the cable, and even above. Most failed long before the cable. Unlike a double screwed connector.
Almost always the crimp. Could be worse because it is flex. Replacing with a proper spade etc using the correct crimp tool sorts it. Of course no connector lasts for ever. But a decent one a lot longer.
I've got a few ratchet tools for those RBY terminals. None is adjustable.
While true for things like your example of taking a feed to run a light fitting from a 32A socket circuit, its not universally true... For example, an unfused 2.5mm^2 spur from a 4mm^2 radial protected by a B32 MCB.
There is also some nuance in "protect" here. The fusing etc must provide fault protection to the whole circuit, but may not be required to provide overload protection to it all. (a spur from a ring circuit being one example - the 32A MCB will provide fault protection for the single run of 2.5mm^2 cable on the spur, but not overload protection. That job is delegated to the design limitation on the spur of only feeding one single or double socket).
With 6A lighting circuits, the cable sizes are over specified anyway with regards to maximum operating current (for reasons of mechanical durability, and limiting voltage drop).
If its the one I am thinking of[1], none of the connectors failed at the full rating of the cable. In fact they all survived well beyond a significant overload - ultimately the cable failed before the connectors
- although that was a moot point since nothing had any insulation left on it at that point (90A though a 2.5mm^2 wire)
[1]
I'm now more puzzled than before. I could look at the book but its not to hand.
Earlier it was said "No, cable should be the same size throughout the circuit. 1mm is actually adequate for most 6A lighting circuits in houses where the cable length isn't too long."
I thought this wasn't true at the time. Can we confirm that as long as the smallest conductor is still fault and overload protected by a MCB, then all is well?
RCBOs are OK for a new installation but probably wouldn't fit on the Wylex board fitted c1992, judging by the space occupied by the MCBs. I'd definitely go for 100mA/30mA RCDs and then RCBOs in a new installation.
As a general principle you would normally have just one size of cable in a circuit, but there are some exceptions as highlighted.
Which bit?
Yup generally. Fault protection in particular is the one critical, must be done at the origin of the circuit, requirements.
If you have a TT installation that is about right (assuming that the
100mA RCD is time delayed if in series with the 30mA RCD).However it will soon be a requirement for lighting to have 30mA RCD protection on new installations. Although this has pretty much been the case since the 17th edition came out.
That's a pity - I've had an experience of enough of a shock to make me jump back - in darkness (assuming that the lighting RCD tripped) I could have suffered an injury on various edges etc.
I can't recall if my 2 RCDs are in series or not; I suppose if 2x30mA are in parallel, then the lighting should stay on if there's a fault on the ring.
Which has always seemed a little superfluous in domestic premises with single phase supplies.
Red - Brown Black - Blue
There's no mistaking which is live or neutral in either case.
SteveW
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