Help an Aussie understand.
The fuse connected to the spur, where is that physically situated in the installation? alongside the outlet, back in the switchboard, or somewhere else?
and do you guys still use fuses, or is that your name for a breaker?
A ring circuit has two actives in the bottom of the main breaker and two neutrals in the neutral link?
The fuse connected to the spur, where is that physically situated in the installation? alongside the outlet, back in the switchboard, or somewhere else?
and do you guys still use fuses, or is that your name for a breaker?
A ring circuit has two actives in the bottom of the main breaker and two neutrals in the neutral link?
To spur off a RFC with multiple outlets, you must have a Fused spur as the first outlet then your socket outlets as described in the diagram posted earlier, the fuse in question will be a cartridge fuse housed in the fused spur unit max size 13 Amps, hence the max allowed in the socket outlets you feed from that Fused spur unit will be limited to 13 Amps, the RFC may still be protected via a MCB at the CU, does the existing RFC have RCD protection? Hope that makes sense.
No Mate not imbedded in the socket The switched fused spur unit is a separate unit, roughly the same size as a socket, used for fusing down when you are connecting lower load, difficult to explain to a non Brit, the fi/use is of the type used in 13Amp UK plug tops, google "switched fused unit" it may explain "a picture is worth a thousand words" as they say
switched fused spur connection unit - Bing
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We use both fuses and circuit breakers. Any new consumer unit will be populated with MCBs or RCBOs. Appliance plugs and fused connection units will have fuses.
Fuses are also useful when you need discrimination between upstream/downstream devices.
The fuse is not embedded in the socket, it is held in a faceplate accessory which has the same dimensions as a standard 13A socket outlet.
A spur is a double socket or a single, so taking two singles us wrong in my book
No it isn't technically correct at all. I understand your theory but nevertheless it is incorrect advice.
I said it is not technically correct. But if I was doing an EICR two doubles on a spur would be a code 2, two singles would be a code 3. If two singles were butted together they would look like a double, a couple of meters of cable between and suddenly it's a different ball game. Not saying it's compliant but in practice there is no difference whatsoever, the regulations are not statutory and deviation can be justified where equivalent safety is achieved.
You said not technically correct but acceptable. A two gang socket is type tested with a load of 20A (14A and 6A) across the outlets and whilst in practice this may not be the case it is fact. Based on this a two gang socket will draw no more than 20A, argue this with British Standards. Two one gang sockets have the potential to draw 26A. To apply a departure you could not guarantee a lesser standard of safety is provided by using two one gang sockets.
Because they we've got a 32amp ring main. And appliances with wiring that are designed to handle 13amps max(often less) so we stick a fuse in the plug to protect the appliance, saves on copper.
'Based on this a two gang socket will draw no more than 20a'!!….. Does it have a current limiter then?? A twin socket can, and will, have two 3kw 13a appliances plugged into it just the same as two singles because the plug fits both. The type testing is based on average loadings likely to be applied in average circumstances, the same average circumstances apply whether it is a twin or two singles. British Standards can say what they want, Joe Public will never ever be heard to say. " Ah, two 3kw appliances I need to use, I cant plug those into a twin because it'll only take 20a, I'd better find two separate singles to plug them into".
As I said in practice this may not be the case.
Sure, you are down sizing the fuse so that socket alone can't exceed 13 amps, while the rest of the circuit can. But one needs to ask "why"? Why not just use the protection set aside for the ring circuit? It is still part of the main circuit as an overall load, so why does a stray socket suddenly need it's own fuse?
and why a ring circuit? sure, it splits the load, but why not just make 2 separate circuits? you have already run the cable back to the switchboard. That way you have two separate circuits, both sharing the load of all the sockets... but you have the added advantage of only tripping one circuit at a time, instead of losing power on everything.
I guess it's because the UK wiring systems are the envy of the World!!
I replaced quite a few burnt out MK logic sockets that have been used with 2 x 10A+ loadsI believe MK claim their twin sockets are good for 2x13A loads
"Why?" only applies when the spur is to feed more than one point. A fused spur enables a single cable (2.5mm) rated at < the 32a source OCPD to feed any number of points because the load is limited to 13a. Two twin sockets on an unfused spur would have a load potential exceeding the current carrying capacity of a single 2.5mm cable which could result in thermal damage to that cable.
Take a look at the diagram in post 4 all will become clear
This doesn't make any sense at all. Two unfused sockets doesn't equal "unprotected", it is still protected by the 32 amp breaker (just like all the other sockets on the ring circuit). All you are doing is limiting that socket and any connected after it, to 13 amps. it is still part of the 32 amp circuit.
If two fused sockets is going to exceed the load potential of 2.5 mm, then what do you think all those other sockets going to do to the current carrying capacity of the 2.5 mm in that circuit?
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because we cheap and want to save money on copper and circuit breakers.
Strange opinion - fuses have many uses. Think of discrimination/where you have a submain fed from a fuse.
It doesn't, and I never said Bs7671 says two singles equals one double. I said in my opinion there is no difference in practice because both allow the connection of any two 13a appliances with a 13a plug.
You are completely missing the point. A ring is protected by a 32a breaker because each socket on the ring is effectively fed by TWO 2.5mm cables, not one. If you reduce the supply cable to ONE 2.5mm with a spur off the ring then the load carrying capacity of that part of the circuit is effectively halved, it's no longer capable of carrying 32a. That's why the spur cable would need to have a reduced overcurrent device to protect only the spur if it supplies more than one twin outlet.(or more than one single to be in compliance with the guidance in 7671.
It clearly does say one single or one double. Look in the top/left square, my friend.
The trouble is, anyone can change that single to a double at a later stage... you now have two doubles.
You do know the current carrying capacity of 2.5 mm is a lot more than 13 amps, right? You can easily use a 20 amp breaker to protect a full set of double sockets on a single 2.5 mm circuit.
The fuses are there to protect the flx of the appliance as well, which will always be less than the 2.5mm ring cable (2 x 2.5mm!)
Different fuses for different appliances.
Most common are 13A for larger appliances, and 3A for lamps, tv’s etc.
If a fault develops in an appliance, and We didn’t have a fuse in line, the flex could melt before any 32A circuit breaker senses the over current.
The uk did used to have 15A and 5A unfused plugs but they went out of regular use decades ago.
( I will be corrected on that, I’m sure, as these unfused plugs are still used in some specialised places)
Different fuses for different appliances.
Most common are 13A for larger appliances, and 3A for lamps, tv’s etc.
If a fault develops in an appliance, and We didn’t have a fuse in line, the flex could melt before any 32A circuit breaker senses the over current.
The uk did used to have 15A and 5A unfused plugs but they went out of regular use decades ago.
( I will be corrected on that, I’m sure, as these unfused plugs are still used in some specialised places)
Well 15A unfused round-pin plugs are quite common in stage lighting, but it is true they are not often found in a domestic property nowadays.
Dorman and Smith I believe that's the makers name utilised the fuse as the live oin on their plug tops, some of the old Council houses had them, my Mum and Dad's house had them in Bath the houses were built at or during the end of WW2
This is where the problem is. We would have 20 amp breakers on each power circuit, which allows 20 or more outlets (not connected in a ring). doesn't burn out the flex before tripping the breaker. You can piggy back off other outlets, connect 3 other outlets from one. You guys made it too hard and complicated.
More than 20 outlets seems a bit excessive on one 20A breaker. But you seem to know better than us.
And don't worry, we design circuits so that the protective device trips well before cables start to overheat. Our regs are quite exacting on that matter.
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