Connecting many low-power mains devices (wall warts etc) to single mains socket

[NY]

I have a room that I use as a study. It has only one single mains socket (the other is on the opposite side of the room and would require a long trailing cable to reach the desk area).

I currently have a PC and LCD monitor, and wall-warts for various low-power devices (router, phone, security camera, headphones etc) plugged into a series of multi-way socket blocks (there is a 6-way with two 4-ways plugged into it).

Obviously the overriding factor is that the total current does not exceed 13 A, and when I measured it, it was about 3A.

But is there any safety issue with lots of plugs, via multi-way socket blocks, all going back to a single wall socket? Is there any advantage in having the single socket changed for a dual one and plugging half the appliances (via socket blocks) into one socket and half into the other? Is a single socket block with 12 sockets in any way safer than a 6-way with two

4-ways plugged into it?

[Dave Plowman (News)]

The safety issue is more likely to be tripping over that rat's nest. ;-)

[tabbypurr]

none of those options are a safety issue

NT

[Harry Bloomfield]

NY formulated on Friday :

No safety issues, unless the adaptors are maybe cheap Chinese items. Mainly it will look untidy, but better/safer than a long trailing lead across a walking space.

[Martin Brown]

So long as you stay inside the maximum current rating and don't start plugging kettles and fanheaters into them it should be fine as long as you don't trip up over the cables. You can get 8 way socket blocks.

You might find some advantage in having one smart socket so that when the PC is powered down all the other peripherals are switched off too. Some devices have surprisingly high standby currents...

I caught the church once with two 13A kettles plugged into a mostly still wound up extension cable relying on their deity for protection. The 13A plug was mad hot and the rolled up cable insulation melted!

Apart from tripping up over the rats nest of cables no not really.

[John Rumm]

In terms of total load its fine.

There is a more general danger with cascaded extension leads that the earth loop impedance can rise too much, and then in the event of a fault (say crushing a flex under a chair leg), the fault may not be cleared fast enough to prevent something getting too hot and catching fire. Having said that, with short leads that's unlikely.

It would be neater (and possibly less of a trip hazard). It would also arguably be safer - but its hard to quantify how much. Its probably only worth doing for neatness.

[Brian Gaff]

To be honest the only issues I've found on doing this are trip hazards with the cables and dodgy connections in the socket bars crashing things.

Brian

[Brian Gaff]

However do beware the next person plugging in a fan heater to one of the trailing sockets and either overloading the fuse or more likely, crashing the computer every time the thermostat operates! Brian

[Graham.]

It's fine, and there is even an argument that says a trailing socket bar is safer for wall-warts than plugging them directly into wall sockets.

You sometimes can't be sure that the approval stamps etc. on imported wall-warts are genuine, and without breaking them open there is no way to see if they even contain an internal fuse. The wall socket is probably fused at 32A at the CU, you wouldn't want that to be the only overload protection for your wallwarts. at least with a trailing bar you know there is a 13A fuse in the plug, and in your case I would swap it out for a 5A for further protection.

[Bill Wright]

Leave it all plugged into one socket then there won't be any confusion if you need to kill the power quickly.

Bill

[spuorgelgoog]

I think so, because of earth loop impedance as Mr Rumm states. I made a 10- way block with 5 x double sockets and a plank.

Or sir may wish to spend £25 quid on a ready made one

p/PL14407

or less

PL15128

Owain

[Alan]

Surely that is what the 13A plug fuse is for?

2.5 Ohms max ZS for a 13A fuse, almost double the requirement for a 32A circuit.

[John Rumm]

It much depends on the lead lengths (and a little on the quality of the sockets etc). In the case of short multi-way leads its very unlikely to be an issue unless the circuit feeding the socket is well out of spec.

For a 13A fuse you probably want 95A of fault current to be sure of being inside the typically required 0.4 secs disconnect time. So that means about 2.4 Ohms at 230V. You could lose 1.44 ohms off that before you even get to the plug on 32A circuit at maximum length.

So 40m is about your limit. Use multiple cascaded leads and it could be quite significantly less due to the extra plug and socket connections.

[dr.s.lartius]

Electrically, I expect no problem. Ensure that the other socket is visible and accessible, and that anyone who has cause, real or imaginary, to use e lectricity in that room for other purposes - handymen, family, friends, you rself, etc. - uses only that socket.

As you seem to be doing, daisy-chain as little as reasonably possible.

If possible, mount all of the distribution on fixed boards. Group the conn ections so that whatever you want always on is separate from what you switc h off at night, etc.

Be aware that one can now buy small three-way switched adaptors - cubes wit h one male BS1363, three females, a trio of switches, one blank side.

ASIDE - caveat on adaptors : I have one - 4-way switched plus straight-thro ugh - from a moderately respectable supplier. Electrically, seems OK. But I ran a 2kW fan heater on the straight-through for a while - and later fou nd that the heater would not unplug from the adapter, except by tool-assist ed brute force. Evidently one pin had made poor contact, and the body of t he adaptor was thermoplastic.

[Steve Walker]

From what I have heard, it is not recommended to daisychain multiple multi-way sockets as it can increase the earth impedance and breach fault trip times. Two into one won't be a problem though.

SteveW

[NY]

No, I would only have two levels of multi-way sockets and not go beyond that. I much prefer flat multi-way blocks rather than the older style of cubic blocks that can feed three plugs, because I've found those sometimes running a bit hot with something like a 1.4 kW vacuum cleaner.

Sadly our house is of an age where all the sockets are single rather than dual, and are not very sensibly placed within rooms. For example the bedroom that I use as a study has only one wall where a bedhead could be placed, because of windows on one wall, fitted wardrobe on another and chimney breast from fire downstairs on third. And yet neither of the sockets in that room are on the bed head wall (for reading lamps) and one is behind a door where it is unlikely any device (lamp, etc) might be placed. Hence my problem with having to power all the paraphernalia of modern life from a single socket (the one behind the door is no use to man nor beast, except for transient things like plugging in the hoover).

Oh, and I'm aware of the rat's nest problem. I really *must* coil/bunch up the longer cables to keep them as far away as possible from my feet under the desk. Trouble is, as soon as you do that, you find the you need to unplug and move something, hence needing to undo the Velcro ties that are keeping everything tidy - I think it's a sub-clause of Sod's Law that you never need to move anything until you've tied all the cables back to keep them tidy :-)

[Dave Plowman (News)]

Best not to daisy chain, but feed as radials from one.

[Clive George]

If you're feeling keen, you could shorten the leads to the correct length so no velcro or coiling/bunching.

[Andrew Gabriel]

You need to add the resistance of the appliance flex too. The rules don't really allow for extension leads. Hence the max length of an extension lead is 12m for 1.25mm², and 15m for 1.5mm² cable (PAT testing guidelines). Rules don't allow for adding of contact and fuse resistances either, hence a reason not to daisy-chain them, and they're almost never the quality of a proper 13A wall outlet.

I managed to pick up a few from an old employer for peanuts where the extension lead sockets are actually MK 13A round panel mounting sockets, but these were damn expensive to make, and the company manufacturered them itself. There was enough space inside to add a mains relay per socket, so I have each socket individually switchable via my home automation.

[John Rumm]

Indeed, although that's a bit harder to factor without knowing what is plugged in.

Yup, I expect my 50m 1.5mm^2 JoJo lead is probably out of spec more often than its in it! ;-)

Handy...