spur on a spur in the loft lighting circuit

[KevinPeters]

Hi all
I am pretty sure of something but I just want to check.

Currently I have taken a spur (via a junction box) off the lighting circuit in the loft. From the JB, there is a FCU with a 3A fuse, then from that is a triple socket (right underneath it, also with a 3A fuse). I have a suitable warning label on both the socket and the FCU.

I would like to spur another triple socket off the first. My understanding is that this is ok, because they are on a fused spur.

Please confirm that this would meet current regs.

Thanks
Kevin

p.s. in case you are wondering, I have a modem, switch, telephone base station, aerial booster and server attached - total load is well under 3A.

 

[ericmark]

No not permitted.

314.1 Every installation shall be divided into circuits, as necessary, to:
(i) avoid hazards and minimize inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance (see also Section 537)
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation
(v) mitigate the effects of electromagnetic interferences (EMI)
(vi) prevent the indirect energizing of a circuit intended to be isolated.
314.2 Separate circuits shall be provided for parts of the installation which need to be separately controlled, in such a way that those circuits are not affected by the failure of other circuits, and due account shall be taken of the consequences of the operation of any single protective device.

It is early in BS7671:2008 and what it is saying is overloading a socket should not cause the lights to fail.

Yes I know it is common for the TV booster to be feed from the lighting circuit the same goes for the bathroom fan. Well one must use some common sense and for these items drawing milliwatts then turning a blind eye may be OK.

In the main because we use ceiling roses which are only rated at 5A we can only supply the lighting with a 6A MCB. The MCB likely is a B type so under fault conditions it is likely the B6 MCB will trip before a 3A fuse.

If you use a 1A fuse then maybe it will rupture before the MCB trips but 6 sockets from a lighting circuit must be OTT.

OK today it is no longer illegal to run non lighting items from a lighting circuit pre-war many were fined for doing that. But it is not really a good idea.

 

[dhutch]

Im mainly interested by what six items your planning to plug in with a total draw of less than 3amps? Thats a lot of TV boosters, network hubs, nas drives....

Daniel

 

[JohnW2]

No not permitted. ... 314.1 ... 314.2 ... what it is saying is overloading a socket should not cause the lights to fail. ... Yes I know it is common for the TV booster to be feed from the lighting circuit the same goes for the bathroom fan. Well one must use some common sense and for these items drawing milliwatts then turning a blind eye may be OK. ... If you use a 1A fuse then maybe it will rupture before the MCB trips but 6 sockets from a lighting circuit must be OTT.

You're essentially saying that there should never be any sockets on a lighting circuit (at least, not on a 3A fuse), since one could obviously overload the circuit with just one socket outlet, let alone 6. However, as you say, common sense is often necessary, and I think that most people would accept very small, essentially 'fixed' (often 24/7) loads as not representing significant risks of circuit overload. If the OP's list did not include 'server' (which could mean anything, and hence needs clarification), I might be tempted to invoke 'common sense' in this case.

In terms of pragmaticism, what one always has to remember is that if someone is persuaded not to do as the OP has proposed, there is then often a risk that they will simply plug in a 6-way extension lead into one of the existing sockets!

Kind Regards, John

 

[KevinPeters]

Thank you for your answers everyone.

Daniel: you will find the items I would like to power stated in my post.

John: To clarify server, I essentially mean a NAS, i.e. < 50w max.

Eric: I would agree with John that your interpretation would not permit anything plugged into the lighting circuit, which would go against the recommendations that I have seen it is OK to plug low load devices in as long as you:
1. use a 3A fuse in an FCU
2. Label it with a warning.

Now admittedly, I have taken it to extremes with a triple socket and mutiple devices, but from what I can tell I am still (currently) compliant with the regs. I agree that going to 6 sockets will take it to the other side of 'common sense'.

However, as John has rightly pointed out, I am currently using a 4-way power strip on one of the sockets anyway.

TBH I am just about under 1A with everything attached as they are all low-load and permanent fixtures.

I guess the answer isn't so clear cut, but what I am trying to achieve does go beyond 'common sense'. Therefore I will leave it as is for the time being. (Next year when I decorate the upstairs hallway I will extend the ring main into the loft).

Thanks again for all your help.
Kevin

 

[EFLImpudence]

I did start replying with the intention of saying that it is just an electrical circuit to which, with proper design, anything could be connected.

However, does table 52.3 prohibit what the OP is proposing?

I.e. if the 'lighting circuit' is in 1mm² conductors, can it be used to 'power' appliances.
Were it in 1.5mm² then it would indeed be just an electrical circuit to which, with proper design, anything could be connected.

 

[JohnW2]

I did start replying with the intention of saying that it is just an electrical circuit to which, with proper design, anything could be connected.

Indeed - which I suppose isn't that far from what I was trying to say.

However, does table 52.3 prohibit what the OP is proposing? I.e. if the 'lighting circuit' is in 1mm² conductors, can it be used to 'power' appliances. Were it in 1.5mm² then it would indeed be just an electrical circuit to which, with proper design, anything could be connected.

Very good point. I think you're right (about 1mm² cable), and I hadn't thought of that one. However, you are at risk of opening up a whole can of worms - unless you would classify extractor fans (or even shaver sockets) as 'lighting'

Kind Regards, John

 

[rjm2k]

unless you would classify extractor fans (or even shaver sockets) as 'lighting'

Or something designed to run off a lighting circuit?

 

[JohnW2]

...unless you would classify extractor fans (or even shaver sockets) as 'lighting'

Or something designed to run off a lighting circuit?

Table 52.3 says nothing about that - it's just 'lighting' !

Kind Regards, John

 

[dhutch]

Sorry, missed the bottom line of the opening post.

I have to admit, I would in the situation, just stick a 6way into one of the exisiting sockets.... either that or I would take a spur from the ring main, which is what I actaully did in my own house.


Daniel

 

[ban-all-sheds]

To clarify server, I essentially mean a NAS, i.e. < 50w max.

Less than 50W for several disk drives, a network adapter, RAID controller, possibly processing power for a filesystem?

Inrush current on startup really less than 200mA?

 

[KevinPeters]

Well I said nothing about several disk drives, network, RAID etc.

So, yes less than 50w.

Let me be specific.: It is an HP Microserver N40L with 2 x 3.5" hard drives. Peak load at startup is 40-50W.

http://www.youtube.com/watch?v=2zbjGywEkTA

 

[ericmark]

I think you need to separate two questions.
1) Will it comply with the regulations? To that the answer seems plain "No".
2) Does it present a real danger and would you do it?

Now here there is a more considered answer. One drops into method statements and risk assessments.

So with the proposed method i.e. a 3A fuse feeding all sockets is there a risk of:-
1) Losing lighting.
2) Danger as a result of losing lighting.

Now in my house stairs and landing are lit by a emergency fitting and there are windows above the doors of each bedroom so losing the lighting circuit would not be a danger.

That is just an example. Now you say 50W max so would seem a 1A fuse would be enough that will give 230W so using a 1A fuse you would be very unlikely to lose lighting due to a fault on the equipment being plugged in.

But clearly we can't tell you to break the rules you must take that responsibility and accept next time an inspection is done it will fail.

 

[JohnW2]

But clearly we can't tell you to break the rules you must take that responsibility and accept next time an inspection is done it will fail.

As a matter of interest, how would you assess the relative risk of doing as proposed and 'the alternative', which would presumably be to plug in a 6-way (or maybe 4-way) extension into the existing socket (and unplug it prior to that inspection!)?

Kind Regards, John

 

[dhutch]

As a matter of interest, how would you assess the relative risk of doing as proposed and 'the alternative', which would presumably be to plug in a 6-way (or maybe 4-way) extension into the existing socket (and unplug it prior to that inspection!)?

Kind Regards, John

Personally I would see that as effectivly the same set up and hence simular risk. The real alternative is to extent the ring main or a spur from the ring main into the attic, or run a spur direct from the CU.

Daniel