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Topic Title: Testing a lighting circuit fused down off the ring
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Created On: 19 March 2013 05:24 PM
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 19 March 2013 05:24 PM
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Jaywn

Posts: 7
Joined: 22 February 2012

Hi all.

When testing a lighting circuit fused down off the ring do I put it down on the test sheet as a separate circuit or mark it on the sheet that it's a spur?

Thanks.
 19 March 2013 05:34 PM
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AJJewsbury

Posts: 11784
Joined: 13 August 2003

There's always a debate about that one!

For me, it's another circuit, so I'd put it on its own line on the schedule, indented below the ring prefixed with a sort of L mark to suggest it's fed from the circuit above. That way you can list the BS 1362 as the protective device with an appropriate max Zs etc - which is useful if the actual Zs exceeds the ring device's limit. It also means you don't have to feel uncomfortable about bits of a ring containing 1mm2 conductors (table 52.3 and all that).

- Andy.
 19 March 2013 07:09 PM
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daveparry1

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Personally I record the ring figures and note on the mwc/eic that the addition is fed via a fused connection unit from that circuit. As Andy mentions, very often the Zs does exceed the max for the protective device but I still consider it's all one circuit and just hope that anyone that's reading the eic has enough knowledge to understand the results!

Dave.
 20 March 2013 11:23 AM
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primo

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That's cleared that one up then!
I'd be happy with either of the above methods.
 20 March 2013 07:34 PM
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Jaywn

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Thank you all for your answers.
 20 March 2013 09:58 PM
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leckie

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So Andy, you consider a fan fused at 3A from a lighting circuit to be a new circuit as well?
 21 March 2013 09:25 AM
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AJJewsbury

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So Andy, you consider a fan fused at 3A from a lighting circuit to be a new circuit as well?

Certainly.
- Andy.
 21 March 2013 09:34 AM
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zeeper

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I would suggest looking at appendix 15, page 425, bs7671, and then looking up spur in definitions page 34 bs7671 before making up your mind.
 21 March 2013 09:58 AM
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AJJewsbury

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I would suggest looking at appendix 15, page 425, bs7671, and then looking up spur in definitions page 34 bs7671 before making up your mind.

I didn't think the definition of a circuit (page 24) gave much room for manoeuvre. A spur of course can be fused or unfused - the unfused variety would of course be the same circuit. Appendix 15 doesn't explicitly say whether it considers fused spurs to be new circuits or not - despite the usual English meaning, there's nothing in the BS 7671 definition of a final circuit to prevent it supplying other circuits as well as sockets/fixed equipment.

- Andy.
 21 March 2013 11:47 AM
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zeeper

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final circuit to prevent it supplying other circuits


That was kind of what my angle was, how can a final circuit feed another circuit.
I guess you can stretch the regs but I think the guidance of appendix 15 is clear.

may be one day bs will clear this up
 21 March 2013 12:14 PM
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AJJewsbury

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That was kind of what my angle was, how can a final circuit feed another circuit.

I suspect the language dates from the days when each (round pin) socket, machine etc was supposed to have its own dedicated circuits (when radials really did just radiate out from the fuse board) and has been overtaken my "modern" approaches of feeding multiple items from a circuit.

I think the guidance of appendix 15 is clear.

It might not contradict your point of view, but it doesn't seem to contradict mine either

- Andy.
 21 March 2013 12:39 PM
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rogersmith7671

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Quote;
When testing a lighting circuit fused down off the ring do I put it down on the test sheet as a separate circuit or mark it on the sheet that it's a spur?

Put it down on the test sheet as a circuit. If test results (measured at final point) of this particular Spur (a branch from a ring or radial final circuit) are higher than those for the rest of the final circuit, then note these on the report.
You can always refer to any danger this situation may give rise to, on additional comments.

Regards
 22 March 2013 07:17 AM
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zeeper

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If you open up OSG to page 68 ," 7.2 standard final circuits".
Now look down to socket outlet circuits 7.2.2. I think again this gives a clear indication that a spur is part of the final circuit.


just one more point, GN3 page 37 mentions higher readings for spurs and says this reading is to be recorded as R1+R2 for the ring final circuit.
 22 March 2013 07:23 AM
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leckie

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Well if a spur via fused spur is considered an extra circuit that would make for a lot of extra work on a certificate!

Boiler, couple of fans, intruder alarm, appliance via sw fused spurs, etc. Sorry but the only time I might add info to a certificate would be if the Zs on a spur exceeded the max value permitted of the circuit protective device but was within the limit for the BS1362 device.
 22 March 2013 09:23 AM
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AJJewsbury

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If you open up OSG to page 68 ," 7.2 standard final circuits".

And what's the definition of a "final circuit"? (the BS 7671 one, not guessed at from ordinary English)? Does it say it can feed only sockets & current using equipment and not another circuit as well?

just one more point, GN3 page 37 mentions higher readings for spurs and says this reading is to be recorded as R1+R2 for the ring final circuit.

For spurs - as distinct from fused spurs - that's perfectly correct.

only time I might add info to a certificate would be if the Zs on a spur exceeded the max value permitted of the circuit protective device but was within the limit for the BS1362 device.

So you're happy to treat it as a separate circuit when it suits you?

- Andy.
 22 March 2013 09:37 PM
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leckie

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I'm not treating it as a separate circuit when it suits me, I'm just saying that there may be an occasion when compliance needs to be confirmed or detailed. Are you seriously telling me you give the details of each addition to a fused spur? Showing the BS1362 rating, cable size, etc, etc? I have seen thousands of certs and have never seen that done.
 22 March 2013 09:52 PM
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AJJewsbury

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Are you seriously telling me you give the details of each addition to a fused spur?

Personally, yes I do. (I don't however write that many certificates and don't have the commercial pressures of most, so I'm in no position to say what you should be doing!)

I see it the other way around though. Say you have a ring, that supplies the CH controls via a FCU. If you treat that as one big circuit, what are you wring on the certificate for cable live/c.p.c. size? 2.5/1.5 or 0.75 to cover the flex I bet half the CH wiring will be in? If you have a spur taken from a JB or back of a socket that feeds the FCU which then feeds the CH (so an unfused spur feeding a BS 1362 feeding a fused spur) which Zs/R1+R2 values do you measure & which do you write down?

Is what you write down sufficient to show compliance with BS 7671 (not just in ADS disconnection time, but in fault and overload protection)?

- Andy.
 23 March 2013 09:58 AM
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leckie

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Very good point Andy........
But, a 3a fused spur on a circuit supplied via an rcd or rcbo would normally cover all wiring to a heating system wired in .75sq.mm flex.

Should we be recording this on the test sheet? Possibly.

What do others think of this? As I have said, I've never seen this done.

Blooming lot more work on the test result sheet!

As mentioned, the only time I have ever recorded this is when the max Zs for the cpd at the con unit is exceeded on the wiring of a spurred supply.
 23 March 2013 10:28 AM
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ebee

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I think it`s clear that we should be doing, not many, hardly any do though.
I am not claiming complete innocence of that offence either, although for a lighting circuit fused spurred off a ring (or radial) I would do (conservatory for instance) .

I`d better go to the naughty corner now.


I`ll admit that say a kitchen extractor or undercupboard lighting I would not.
Because I consider them being "Like" appliances ie just as part p makes it clear that something on a plug can still be fixed mains wiring and a circuit then something that could be on a plug (and often is) could be connected by a switched FCU , be it washing machine, hair dryer etc etc.

-------------------------
Regards,
Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 24 March 2013 05:09 PM
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leckie

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Well I had a look through a few certificates I have done lately and found I had also filled in a minor works for a lighting circuit added to a ring-main via a sw fused spur. However, if this is regarded as a new circuit then it shouldn't have been a MWC but an EIC! So I got that wrong didn't I?

Never seen a gas/oil central heating spurred from a ring shown on a cert except when the heating w as carried out as an addition.

This has got me thinking because I have never been asked during an niceic assessment about this, and that's going back about 30 years and they have seen certificates for thousands of dwellings with gas fired central heating systems wired.
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