Advice on attic additional socket wiring

SierraTango

I'm looking to add another 2gang socket to my attic. There is currently one 2gang socket which looks like a spur off a room below (only one wire going into it), and a mains wired smoke alarm.

Can I add a socket off the smoke alarm? I presume I can't add off the spur. So would the best best be to try run a cable up from another socket in a room upstairs?

seamus

You can't wire a socket off a smoke alarm. Fitted correctly they're wired either off a lighting loop or directly fed back to the board.

You're correct that you also can't extend the existing socket. If it's a ring main, you can take a spur off another socket downstairs. If you're going for a neat job (i.e. it's an attic office or something), would it be worth getting sparks in to fit a new circuit for the attic completely? A bit of cash, but it'll remove any questions.

GolfNut33

seamus wrote: »

You can't wire a socket off a smoke alarm. Fitted correctly they're wired either off a lighting loop or directly fed back to the board.

You're correct that you also can't extend the existing socket. If it's a ring main, you can take a spur off another socket downstairs. If you're going for a neat job (i.e. it's an attic office or something), would it be worth getting sparks in to fit a new circuit for the attic completely? A bit of cash, but it'll remove any questions.

Nothing wrong with tapping into the existing socket IMO.

mloc123

GolfNut33 wrote: »

Nothing wrong with tapping into the existing socket IMO.

Depends... is it a ring or a radial?

Maewyn Succat

SierraTango wrote: »

I'm looking to add another 2gang socket to my attic. There is currently one 2gang socket which looks like a spur off a room below (only one wire going into it), and a mains wired smoke alarm.

Can I add a socket off the smoke alarm? I presume I can't add off the spur. So would the best best be to try run a cable up from another socket in a room upstairs?

The electrician you hire to do the job will know the best way to do it.

2011

Maewyn Succat wrote: »

The electrician you hire to do the job will know the best way to do it.

You would like to think so but unfortunately the quality of RECs varies considerably. Getting information here from experienced electricians / engineers / and other technical professionals provides posters that have only limited experience some understanding of an electrical installation. Sometimes this is used to support a RECs position on something other times it can be used to challenge it.

Maewyn Succat

2011 wrote: »

You would like to think so but unfortunately the quality of RECs varies considerably. Getting information here from experienced electricians / engineers / and other technical professionals provides posters that have only limited experience some understanding of an electrical installation. Sometimes this is used to support a RECs position on something other times it can be used to challenge it.

I was really just making a point that the OP shouldn't do the job himself. Anyone who even considers wiring a socket from a smoke alarm shouldn't perform electrical work of any kind.

2011

Maewyn Succat wrote: »

I was really just making a point that the OP shouldn't do the job himself. Anyone who even considers wiring a socket from a smoke alarm shouldn't perform electrical work of any kind.

Understood.
However putting all your faith in what some RECs tell you would be inadvisable.

Bruthal

The source of the existing socket would need to be checked.

An extra socket can be added to a ring, but the ring needs to include the new socket, as in the new socket becomes part of the ring, rather than a single cable spurred off the ring to the socket.

Once suggestions are being made of connecting the new socket to the smoke alarm, without any understanding of the implications if the smoke is correctly installed already, then its time to get in a suitably qualified person.

Citizenpain

What are you using it for?
Would a long extension cable work? Depending on neat your attic is

adrian92

I would think no problem using the existing socket to supply another socket, unless there is a significant change in load.

Modern loads , generally are very low- we have this ancient system that every socket must supply 3000 watts , when it is usually a few watt of load per socket outlet

2011

adrian92 wrote: »

I would think no problem using the existing socket to supply another socket, unless there is a significant change in load.

It may well be no problem, but as you allude to there may be a “significant change in load” so it needs to be checked.

As I am sure you know the rules limit the number of socket outlets per radial circuit (10 points) as well as the number of rooms they can serve (to 2 not including a hallway). So this would be another reason to check.

Modern loads , generally are very low- we have this ancient system that every socket must supply 3000 watts , when it is usually a few watt of load per socket outlet

Yes, generally. But sometimes they supply larger loads such as electric heaters.

SierraTango

Cheers for the advice. I'd be using it to power a modem and a network switch.

I'll probably give a sparks a shout so, seems like the best idea!

2011

SierraTango wrote: »

Cheers for the advice. I'd be using it to power a modem and a network switch.

From an electrical perspective these are very small loads. However it is always good to check the existing circuit to ensure that it is fit for purpose before modifying it.

I'll probably give a sparks a shout so, seems like the best idea!

Good call.

TheBully

mloc123 wrote: »

Depends... is it a ring or a radial?

Genuine question, what is the issue with running a spur off a ring?

2011

TheBully wrote: »

Genuine question, what is the issue with running a spur off a ring?

Depends on how it is done. Generally a ring is wired using 2.5mm sq. conductors. MCBs rated at 32A would not provided sufficient over current protection to a cable this size. If wired in ring then the high MCB rating is not an issue as the load is shared, but a spured section would not have the benefit of being able to share the load with another cable.

adrian92

About 90 watts added, maximum.
No problem.

Sometimes the rules don't take into account common sense.

2011

adrian92 wrote: »

About 90 watts added, maximum.
No problem.

Sometimes the rules don't take into account common sense.

Sometimes. With respect we have no idea whether it is a problem or not.

Just because the planned new load is small it doesn’t necessarily follow that the entire circuit fit for purpose.

More to the point, it would also be foolish to assume that a far larger kid would never be plugged into the new socket.

adrian92

2011 wrote: »

Sometimes. With respect we have no idea whether it is a problem or not.

Just because the planned new load is small it doesn’t necessarily follow that the entire circuit fit for purpose.

More to the point, it would also be foolish to assume that a far larger kid would never be plugged into the new socket.

Moderator, I fully accept your point, on reflection. No one can know how a power outlet can be used in the future.
I would like to withdraw what I said

2011

That’s ok, it’s not a competition:)

The man that never made a mistake never made anything.