Hello,
I have bought some round pin plugs to use with table lamps. I bought the 5A variety as I can't seem to find the 2A ones: have they gone out of fashion?
I've never used them before. I was expecting them to be identical to mains three pin plugs but with different shaped pins. However, I see that there is no fuse inside. Is there a reason for this? You can get
2A and 5A fuses, so why not bring them up to date and fit a fuse on the live pin, as with 13A plugs?Thanks.
Round pin plugs preceded what you call "mains three pin plugs" and were never fused, being used on (mostly) radial circuits where the protective fusing was done in the consumer unit (or fuse box as it was known then). The increased use of appliances and the development of the ring main to serve them meant that local plug top fuse was essential for adequate protection as the consumer unit protection is to protect the ring main, not the individual appliance connection. Small 5A plugs are still for sale to connect lights etc to lighting circuits that are protected by a low (usually 5A) fuse anyway. This prevents normal applicances being plugged in. What you should
*not* do is connect a small round pin socket to a ring main! They should be connected to the normal lighting circuit or a fused spur off the ring main with a 5A fuse (or lower). all AFAICR and IMHO
Yes. I don't think they were ever particularly common. 5A and 15A are / were used for theatre wiring. 2A isn't a good match for a 5/6A lighting circuit.
They are unfused because they were wired on radial circuits which had the correct fuse at the fuseboard.
Owain
TLC still sell the 2 amp ones
There are (were?) fused ones available more recently from MK, but I don't know if they still do them. They weren't ever fused back when they were the normal plug type.
2A ones could be used on circuits fused at up to 10A (this was the common setup for commercial lighting). I'm not sure, but I suspect the 5A ones (and definitely the 15A ones) were allowed on circuits fused at up to 15A.
My father said that when he was young tehre were 'heating' sockets and 'lighting' sockets. later these became the 15A and 5A round pin sockets but in the early days there was more variety.
he said the 'heating' sockets had cheaper electricity than the lighting ones and you were not allowed to plug a lamp into a heating socket - not sure when that ended.
Robert
'13 amp' plugs have a fuse in them because the actual circuit is 32 amps. Round pin plugs are meant to be used on a radial circuit where the protection at the CU is correct for the outlet - ie if it's a five amp plug the MCB should be 5 amp too. They're normally used for things like lighting outlets - and lighting circuits are commonly 6 amp radials. If you wish to fit one to a final ring circuit it should be protected by an FCU with suitable fuse.
2 amp three pin are still readily available - TLC have them in most of their ranges. But since they use the same 1 gang size as 5 amp it doesn't make much difference.
You can still get them at B&Q - even the smaller branches.
AIUI they're preferred for theatre lighting /because/ they're unfused. Not so easy to change a plugtop fuse when the light's on a gantry 20 foot up above a stage. (Of course circuit protection is - or should be - arranged elsewhere.)
IIRC the current availability is 5A and 3A, not 2A.
Both are available, but are not fused.
They never were. Their use in lighting circuits coincided with the CU introduction and properly fused spurs..lighting is not normally wired ring, so there is no reason to fuse the CU AND the plug, as all the wires in question can take the full 6A rated current.
i.e. the reason 13A plugs are fused is on account of ring mains: in theory you can e.g. deliver 32A to a ring main socket, which is in excess of the cable rating to the device.
I am not sure what the current use of 3A stuff is. But its probably restricted to switched fused spurs or similar.
Yes - they're all radial circuits from the dimmer pack, each channel of which is protected.
No, it's 15A, 5A, 2A, as always. (There used to be a 30A too.)
Well, the 2A sockets were used on 5A and 10A circuits.
Nothing to do with ring circuit -- it's because the circuit's fault and/or overload protection is out of scope for the appliance flex, and applies to ring and branch circuits.
I can't imagine what you're referring to.
I hadn't realised they had got around to sleeving the pins on them until I saw the TLC illustration.
Can't think why the OP seems to be wanting to go down this route.
Useful for things like table lights on dimmer circuits - if you have them on 13 amp plugs 'someone' may plug in an appliance that overloads the dimmer.
On a trip to the US, I was staying in a rented condo. Some electrical appliances semed to only work intermittently.
I traced the fault....
The place was full of dual 110v outlets. Some of these dual outlets ( not all ) had one output fed from the light switch on the wall. The intention was to have lamps around the room come on with the light switch.
This didn't work, because all the lamps were plugged into regular unswitched outputs, and required you to go around switching them all on manually at the lamp ( with the horrible rotaty-rotaty US style lamp switches ). The TV and other things OTOH switched on and off with the 'non-functional' light switch!
After a half-hour with a test lamp, I was able to determine which outlets were switched, and which were not. Re-plugging the appliances to the appropriate sockets, and suddenly everything works as expected. The light switch on the wall now actually brought on the lamps in the room.
There was nothing to distinguish the switched from unswitched outlets, except trial and error.
On subsequent trips, I have come across this often, but now recognise the problem straight away!
Presumably there's nothing inherently bad about doing so, though -
*provided* that the fuse for the appropriate ring is chosen accordingly?
I still have a 1942 letter from the power company on just that topic
heating
AWEM
=A0 London SW
Or just switched table/etc lights - to stop people plugging a fan heater into a lighting circuit.
Yes, really: even if you were to protect your ring main at 2A or 5A to suit the unfused round pin socket, it would violate the Principle of Least Surprise, and Sod's Law says someone would come along and replace the fuse or breaker with a 30/32A one "because it's a ring main (innit)".
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