Using wiring for attic light socket as plug socket?

[John Rumm]

Indeed... although it does depend on what the main circuit is protected with. There are some 10A lighting circuits about which will offer more scope.

[Roger Mills]

Except that that will take out the lights, too - plunging the attic into darkness!

Unless you make up a short extension lead with an in-line 13A socket at one end and a more appropriate plug at the other.

[Muddymike]

In article , Muddymike

This is a DIY group. Not every DIY person has a full grasp of professional terminology including myself. He made the situation perfectly clear in the first sentence (which I notice has been clipped out) explaining what he wanted to do.

Asking, what type of double plug socket? May have been constructive, commenting "Make your mind up, a plug or a socket? They are two different things." Just makes the writer sound like a smart arse with nothing to contribute!

That remains my opinion.

Mike

[fred]

In article , Muddymike writes

Professional terminology like 13A socket ;-)

Actually you're quite right and it's a helpful reminder, never a negative without a positive[1], so it's fine to make a correction but only after offering a solution or constructive suggestion on the problem at hand which was not done in the case you pointed out.

My bessie mate has the 'plug socket' mental block and I am have no reservations about ripping the piss out of him over it but he is a software engineer and so cannot be expected to have a grasp of the real world.

[1] There are no prizes for finding instances where I have failed to do this but I sit suitably reminded for the future.

[Dave Plowman (News)]

Plug, pins, penis?

[Johny B Good]

Electrically speaking, you can wire a 13A socket straight off the lighting wiring without compromising safety, provided the lighting circuit remains fused at its 6 amp maximum limit.

If you're fitting a 13A socket in the loft or attic, it's usually for the purposes of providing power to something like a masthead amp or TV aerial distribution amp both of which would be more than amply served by a half amp fuse[1] which minimises the risk of a house fire should a fault develop on the (now fused) 13A socket spur.

Of course, there still remains the risk of a fire from a fault in the amplifier kit itself but, provided it has been designed to the mandatory safety requirements for such 'domestic appliances' this aught to eliminate such risk. The only problem is that, unlike a radio or hairdrier, it is operating 'out of sight' of any human supervision.

I'd be inclined to mount such devices on a metal shelf with heat resistant deflectors (steel sheeting) to stop any flamage from reaching any flamable construction materials and, for good measure, install a loud smoke detector above, but to one side of said kit, ideally with a repeater just outside of the loft hatchway or attic doorway.

In my case, that last bit of paranoia has remained merely an idle inclination to this day (although I might try the smoke alarm idea).

[1] If you needed to provide power for powertools, you'd just plug in a suitable mains lead extension into one of your regular 13A sockets unless you were planning on turning your attic into a workshop (in which case we wouldn't be discussing the use of a lighting circuit feed for a 13A socket now, would we?).

Fitting a 13A fused box in the spur feed to the 13A socket allows you to fit a half or 1 amp fuse which will be more than ample for the socket's intended purpose yet reduce the risk of a fault on the spur from blacking out that lighting circuit. It's just a matter of "Good Practice" and common sense to splash out on such a 'luxury item'.

The same applies to fusing up 30A ring main circuits with lower rated fuses when appropriate. My top floor ring main currently has a 15A fuse link fitted because the only loads are my son's "HiFi" and widescreen TV and computer stuff with no 2kW electric fan heaters in sight.

The 15A fuse link has never blown in the past 7 or 8 years since I downgraded the circuit to a "15A Ring Main". The risk of a fire in the ring main circuit, though slight enough to be deemed acceptable according to the regulations is now somewhat safer again.

I like the principle that you can replace a large fuse link in an existing fuse carrier with smaller rated fuse links (Wylex CU) since it makes it very simple to downgrade the ciruit capacity on an as needed basis without compromising safety (in this case, boosting safety), since it's a trivial exercise to refit the original larger fuse should the smaller one blow due to unanticipated overload.

[Johny B Good]

+1 And, if possible a half amp fuse (the actual draw for a typical aerial amplifier will be way less than 0.1A). The lower the better in this instance.

[Bill Wright]

From Day One of my self-employment I've used 3A fuses to protect TV amplifiers etc. I've always bought a big bagful. During my recent month-long stock room clear out I found three large bags of 3A fuses, all partly used. In volume terms I'd say I have over a litre of 3A fuses. It seems unlikely that I will need these for my domestic requirements.

Bill

[Bill Wright]

Some electricians always used a fit a 2A socket in the loft for us. I put a little amp in every loft on an 80 dwelling job, and I got pretty adept at fitting them liddle plugs. It worried me that there was no plug top fuse but the experts waved their hands airily and assured me that there wouldn't be a problem.

Bill

[Johny B Good]

I suspect such circuits would only qualify for the higher 10A rating when completely wired up with Pyro cabling and appropriate fittings. a more likely scenarion in commercial premises rather than in premises of the domestic persuasion (i.e. a house) where the limit has always been 6A fusing at the CU panel afair.

[Bill Wright]

That can't be right. Software engineers don't have mates.

Bill

[Johny B Good]

Assuming we're dealing with 'modern' lighting circuits which are required to include a protective earth, if you're going to use a FIVE AMP fuse inline, you might as well forego the luxury of such a fuse box connection altogether for your 13A socket spur and just use an ordinary joint box to tap into the lighting circuit.

The 6A fuse or CB at the CU will still provide the same level of fault protection on the lighting circuit and exceed safety requirements for the attached 13A Socket circuit. With a 5A fuse you're just as likely to see the 6A fuse blow (or CB trip) at the CU as you are the 5A cartridge fuse in the spur fuse box.

The extra fuse protection only makes sense with 3A or lower rated fuses fitted. You can always fit a 13A[1] fuse on a temporary basis to allow you to use a powertool or whatever that draws just less than the

6A limit on the lighting circuit with all bar the one lamp switched off whenever you want to avoid the hassle of digging out and setting up a mains extension cord from a regular mains socket. [1] If you're going to swap out the regular 1, 2 or 3 amp fuse, you might as well fit a 13A fuse and work to the 6A limit of the lighting circuit protection.

[Capitol]

Mine is on a 10A ring.

[meow2222]

2A and below suffer much more frequent failure, I expect one of the reasons for the choice of 3A fuses in the 40s.

no :)

Biscuit tins are relatively easy to apply. Snip & bend back the 3 tabs for each hole. They restrict airflow, so a signifcant fire size cant happen. Things can get hot, but fire heat wont add to it significantly.

I've seen whole flats here running on a 5A feed. A pain, but workable. In eastern europe its standard practice to have an 8A feed to flats.

NT

[John Rumm]

10A is well within the capability of even 1.0mm T&E in some cases, and 1.5mm T&E in most.

There used to be a restriction on not using SBC and SES lamp fittings on such circuits, but that was deleted with the issue of the 17th edition.

10A is used domestically as well... I have certainly met it a few times.

[John Rumm]

Well you have two considerations in these cases: overload protection and fault protection. Since its one fixed appliance with little scope for a user to change or alter it, then you can legitimately ignore the possibility of overload. Fault protection must be provided, but you can normally demonstrate that with a small MCB at the origin of the circuit, it will provide adequate protection for even relatively lightweight appliance flexes on your 2A plug.

[Bill Wright]

On one occasion we had a small domestic amp (of reputable make) develop a fault which caused it to make the nearby carpet smoulder (we'd supplied it and left it inside the TV cabinet, but the customer had re-arranged things and screwed it to the skirting board.) The amp had obviously got very hot indeed. It was of a type with a thin walled steel case inside a black plastic case, and the latter had melted quite a bit. The amp had not blown the plug fuse, which was 3A. The smell had alerted the customer when he came home and he had disconnected the power.

Incidentally I've told this before on here, but there was the young mum who, offended by the smell coming from the masthead amplifier power supply, and concerned that it might burn the baby's fingers, wrapped it in towels.

Bill

[Johny B Good]

Well, not being an electrician by trade, I've been unable to find any references to the regulations, only anecdotes regarding 10A lighting circuits (including the use of a ring lighting circuit) so I can't quote 'chapter and verse' as to whether this is an acceptable departure from the regulations or not (I know some leaway exists within the regulations but this seems to be quite a large departure to my mind).

All my knowledge comes from when, with the assistance of a retired electrician (a family relative), I totally rewired this 3 story 6 bed Victorian semi-detached house back around 1983.

This is where I learned about the CU fusing regulations with regard to ring mains, lighting circuits, high power spur feeds to things like cooker points and power showers as well as to the requirement to provide a dedicated 15A fused feed to the immersion heater (classified as a fixed connected load requiringa high temp flex connection between the heater element terminals and the switched terminal box on the end of said dedicated feed). Plus I also learned about the earth bonding requirements of all exposed metalwork (pipework, stainless steel sinks etc).

It isn't exactly rocket science for someone experienced with electronics kit and a well founded knowledge of electrical theory. Once you understand that the fundamental protection provided by the fuse links (MCBs) in a CU is essentially to protect the permanent cabling and fittings it's easy to see why 5A was chosen for lighting and up to 30A for ring mains with 45A protecting 4mm FT&E cabling to a cooker point and other similar heavy duty loads.

A small 3 bed semi can manage with just a single ring main circuit and a single lighting circuit plus cooker point and immersion heater feeds so could be nicely served by a 4 fuse CU with a set of fuses comprising of 5A for the lighting, 15A for the immersion, 30A for the ring main and a 45A for the cooker point.

In a bigger property, you'd be well advised to fit a 6 way CU so you can split the lighting across two circuits, each with their own 5A fuse rather than the ill advised use of a 10A fuse on a single circuit (even when 1.5mm cabling is used - the ratings on the fittings are all based on the protection of a 5A fused supply). Obviously, the second extra fuse position will allow two seperate ring mains to be provided.

When we first moved into the current property, it didn't have a cooker point so I was able to wire up three seperate ring mains (ground floor, first floor and second floor mains socket supplies).

The basement was catered for by fitting 3 single outlet 13A sockets onto the CU backboard each fed off the 3 ring main circuits so that the freezer we kept in the basement could be readily powered from any one of the ring main circuits as an insurance against any protracted outage that might arise due to faults or planned changes in the ring main wiring.

The freezer no longer resides in the basement but the 'diversity' of this setup is still very handy although I have installed an extra twin outlet wall socket away from the CU, connected most likely to the 1st floor ring main circuit (but I'd have to take a gander at the fuse cover labelling to confirm this - but it seems the most logical choice of ring main so I'd be surprised if it were otherwise since the same logic would have dictated my original choice).

When it came to replacing all the VIR cabling in conduit lighting wiring, we knew it had to be split across two lighting circuits. As it happened I bought a couple of 100m reels of 1.5mm FT&E for this job and used nearly all of it.

The Mortgage company had held back £1000 of the loan on account of the state of the lighting circuit wiring but when I delved a little deeper into the state of the rest of the wiring, I discovered the house had two ring circuits and a mix of spur fed outlets randomly distributed about the property (one ring main fed half the ground floor sockets and half the first floor sockets and the other ring main fed all the 2nd floor sockets but with a length of heavy duty rubber sheathed appliance cord being used instead of the regulation FT&E.

What had started out as just a lighting circuit 'rewire' developed into a complete rewiring of the whole house. The job was essentially an exercise in re-organising the randomly fed sockets into 3 distinct ring mains.

Since the top floor was the only proper ring main in the whole house, I replaced the rubber sheathed flex with 2.5mm FT&E to bring it up to standard then dropped a very long mains extension down to the kitchen with another extension lead into the basement to power the freezer whilst I stripped out most of the 'ring main' wiring to the ground and first floor sockets, sorting out the recovered lengths of FT&E so I could rebuild the ring main circuits using shortest lengths first.

This minimised the need to add extra cable to the point where I was able to beg the extra 20 or so metres from my dad thus reducing the cable costs to nil with only the new dual gang 13A sockets as the main parts cost.

It was a lot of work to sort it out but I felt it just had to be done in the interest of safety (it's not good having sockets in the same room powered from different fuses in the CU). needless to say (after sorting out the earth bonding) I had no trouble getting the job certified and the extra grand released by the Mortgage company.

I suspect anyone trying to get their house wiring certified whilst they have a 10A fused lighting circuit in the mix will have a hard time trying to convince an inspector that it is within regs and standard wiring practice.

With many house owners now using CFLs and LED lamps in place of most of the originally fitted 60 and 100 watt incandescent lamps, I think any such 10A lighting circuits could now be 'downgraded' to 5A fuse or

6A mcb protected circuits without any problems.

Other than 'special cases' I think anyone with a 10A fuse protected lighting circuit should downgrade to a 5A fuse for their own peace of mind just on safety grounds alone. Using a 10A fuse, even in a larger domestic property is probably unnecessary with modern lamps these days.

[Tim Watts]

On Wednesday 12 February 2014 03:44 Johny B Good wrote in uk.d-i-y:

10A lighting circuits are "standard" (by the wiring regs) as are 16A (though the latter are almost unheard of domestically).

I have designed by house with 2 x 10A lighting circuits, type C breakers on 1.5mm2 cable to make the system a) able to cope with upto quite a lot of lighting; b) more trip resistant when lamps fail.

I saw no real disadvantages to doing it that way - I prefer 1.5mm2 cable over 1mm2 as I find the latter a little flimsy.

[Johny B Good]

I guess I used 1.5mm at the behest of my "Consultant", probably on account of the fact that we'd need well in excess of 100m of cabling.

According to my "Consultant", the maximum fusing value for lighting circuits was 5A and I accepted this as gospel. Since this protects the ceiling rose and pendant fittings (cordage and lamp holders) as well as the cabling and switches, it seemed to be a logical and sensible restriction (the lower the fuse rating you can use without risking frequent 'fuse blowing' events, the safer it is).

In the past 3 decades since I re-wired the house, I've not had to change a lighting fuse and, afair, only one ring main fuse the one time I carelessly refitted a socket plate onto a new socket I'd added to the ring main (framing fault).

TBH, I can't see the point of mcbs which can have their own peculiar 'failure' modes. A good "Old Fashioned Wylex CU with fuse bridges does the job perfectly fine.

When it's just a matter of resetting a mcb to deal with a mystery intermittent overload, you're more inclined to let things slide than when you have to keep changing fuse links (and rewire the blown fuse links to keep pace with demand).

Fuse protection inclines you to "Do The Right Thing" straight away and fix the actual problem rather than to put it off until you get hold of a "Round Tuit" or have saved up enough money to pay a 'professional' electrician to sort it out for you.

If, like most householders over the past 15 years or so, you have changed a good portion of your tungsten filament GLS lamps over to CFL or LED lamps, you might find that a 6A mcb will now suffice for the reduced loading.

It's certainly worth checking out this possibility since the lower trip value mcb will reduce the risk of a house fire from very small to vanishingly small and it is _this_ hazard such protection is designed to eliminate in the first place.