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Topic Title: Switched neutrals
Topic Summary: Domestic problems
Created On: 24 February 2010 09:49 PM
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 24 February 2010 09:49 PM
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aspiringspark

Posts: 15
Joined: 14 October 2007

Hi Guys, your input ...sil vous plait:-
2 storey domestic property, re-wired in the 80's, at the time TT overhead supply. Main bonding to water pipe in 6mm approx. 10m from CCU, routed via void between ground floor ceiling and 1st floor flooring. Supply has since been changed to PME, each power pole between Tx and property having been earth staked.

The initial concern of the client was that the low energy lights would continually flicker when supposedly off.

However....
Problem 1 is that the upper and lower lighting circuits would appear to have the neutrals switched as opposed to the phase wire
I guess that swapping the phase and neutral wires at the ccu for the offending lower circuit (the upper being accessible in the loft), and then re-sleeving to the correct colours (also at all accessories) would be an allowable option, but what about the inevitable junction boxes covered by carpets and chipboard flooring? Surely the wiring to these must also be correctly identified?

Problem 2 is more of an action to upgrade the main bonding to 10mm.

Client may wear small disruption to property to upgrade bonding, but is not keen to have all flooring ripped up to find hidden junction boxes
to change wire colours.

As the property was wired to presumably the 15th edition, were the wire colours of the time as definitive as they are with the 16th & 17th?

Is there a better solution?

Your comments would be very welcome. Thank you.
 24 February 2010 10:17 PM
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deleted_1_poheZ

Posts: 295
Joined: 12 December 2007

Why worry about junction boxes under the floor? I would just note it on the eic and perhaps make it apparent what you have done to anyone working on the fuesbox. In these situations i ask myself does what i am doing/done make the installation unsafe

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http://southamptonsolar.co.uk
 24 February 2010 10:31 PM
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CarlCosby

Posts: 484
Joined: 16 March 2009

Originally posted by: aspiringspark


The initial concern of the client was that the low energy lights would continually flicker when supposedly off.

Ive come across this, a switch live came loose in a 2 way pull switch which caused this affect. It can also happen if the wiring is done a certain way. Buying better lamps tend to deal with this, assuming the wiring is ok.



However....

Problem 1 is that the upper and lower lighting circuits would appear to have the neutrals switched as opposed to the phase wire

Have the two light circuits been wired to the switches first using double pole switches, and then a single T&E wired to each light? If so then switching the neutrals could cause the low energy lamps to flicker, buying the more expensive make of lamp should fix this, or connecting the neutrals in a connector block (so they are not switched) and changing the DP switches for the 1way, 2way switches should also fix (assuming I have hopefully guessed right your situation)

re-sleeving to the correct colours (also at all accessories) would be an allowable option, but what about the inevitable junction boxes covered by carpets and chipboard flooring? Surely the wiring to these must also be correctly identified?

There's no need to cause damage just to get the wiring colours sorted out under the floor. Make a note of this on the test cert.



-------------------------
Regards
Carl
 24 February 2010 10:50 PM
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Dale76uk

Posts: 412
Joined: 04 February 2010

why dont people use correct terminology?
phase = line
main bonding??? = main protective bonding conductor

We're supposed to know what we're talking about!!
 24 February 2010 11:02 PM
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rocknroll

Posts: 8878
Joined: 03 October 2005

There's always a 'newbie' smart-ass on any forum.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 24 February 2010 11:05 PM
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alancapon

Posts: 5789
Joined: 27 December 2005

Originally posted by: rocknroll
There's always a 'newbie' smart-ass on any forum.




Regards,

Alan.
 24 February 2010 11:05 PM
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Phillron

Posts: 1209
Joined: 18 January 2007

Originally posted by: Dale76uk

why dont people use correct terminology?


We're supposed to know what we're talking about!!




main bonding??? = main protective bonding conductor

That depends on whether you are doing or describing




phase = line
Nothing wrong with that ,they can both have washing before the name
or current after if you prefer

Old habbits die hard
 24 February 2010 11:19 PM
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Dale76uk

Posts: 412
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you'll have to elaborate phillron.....'That depends on whether you are doing or describing'
 24 February 2010 11:29 PM
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Martynduerden

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Originally posted by: Dale76uk

We're supposed to know what we're talking about!!


Does that not suggest that you don't? Main bonding Or Main Protective Bonding Conductor(s) surely you know what the guy means? if he said Earthing that may require clarification ..but I'm sure the context would give the game away Lee!
I thought this was a forum for the initiated ...wrong again I see

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Martyn.

Only a mediocre person is always at their best



www.electrical contractors uk.com
 24 February 2010 11:46 PM
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Phillron

Posts: 1209
Joined: 18 January 2007

Shuks I dont really want to do this ,but Ill do my best

Example


Doing
What the hell is taking so long in that cupboard ?
"I'm doing the main bonding for christs sake"
or we could say
"This main protective bonding conductor is such a tiresome job indeed"

Describing
The earthing conductor has a larger csa than the main protective bonding conductor

Any applause
 24 February 2010 11:48 PM
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Martynduerden

Posts: 3211
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Originally posted by: Phillron


Any applause


well done

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Regards

Martyn.

Only a mediocre person is always at their best



www.electrical contractors uk.com
 25 February 2010 12:12 PM
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Paul1966

Posts: 1538
Joined: 21 December 2004

How is the switch wiring to most of the lights carried out? Is it loop-in at the ceiling fixtures? If so, then surely the mistakes were made at those points during installation, and you could correct everything by just transferring the individual switch drops from each lighting point to the correct side of the circuit. If power is looped through the switches, it should be possible to correct at each switch location. It's going to become more involved if some lights were wired junction-box method though.

Originally posted by: aspiringspark
As the property was wired to presumably the 15th edition, were the wire colours of the time as definitive as they are with the 16th & 17th?


Pretty much, and for many years before the 15th edition too. Red for L, black for N throughout a single-phase installation.
 25 February 2010 02:31 PM
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AJJewsbury

Posts: 11547
Joined: 13 August 2003

Problem 1 is that the upper and lower lighting circuits would appear to have the neutrals switched as opposed to the phase wire

Would seem to be a rather unusual error. How have you identified this? Could it be a simple reverse polarity at a single point, or even mis-identifying faded core colours?
- Andy.
 25 February 2010 04:47 PM
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jockspark

Posts: 195
Joined: 23 February 2008

Originally posted by: Dale76uk

why dont people use correct terminology?

phase = line

main bonding??? = main protective bonding conductor



We're supposed to know what we're talking about!!


anyone else got a problem grasping the terminology ?
most of the guys on here have been in the game 10 years
plus. i have been in the game 35 year its only been line
from 2008 and there is reference to phase in that addition
i think it is clear what the op meant. but there again i am over 25yro
 25 February 2010 05:12 PM
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Paul1966

Posts: 1538
Joined: 21 December 2004

Precisely. You can't easily forget years of use just because some standards committee decides quite arbitrarily to change the "official" definitions at some point.

Look at the IEE Regs./BS7671 definition of "live conductor" for another example. The current definition is not the same as the old definition. Then there's all the changes like an e.c.c. becoming a c.p.c.
 25 February 2010 09:57 PM
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aspiringspark

Posts: 15
Joined: 14 October 2007

Thank you all for your comments, both constructive and corrective!

This was more of a 'can you look at while you're here' situation rather than an actual job. As the property is not within my patch, someone else will be tasked with the fix. The client, as such, requested an insite into the cause of his flickering lights and also the possible disruption (cost) in putting this right.

My quick look involved whipping off a few ceiling rose covers and a couple of wall switch plates, and doing a few polarity tests. It would seem that most switches were wired in 2way mode, using 2way light switches, and that only 1 out of 5 light fittings I tested had the phase wire switched.

Since only 2 of the 5 ceiling roses were wired loop-in, loop-out fashion, I concluded there were obviously hidden junction boxes dotted around.

I also concluded that this must have been a DIY job, hence the strangenous of the wiring and the obvious lack of certification. Ain't that always the case!

By the looks of it:- The main protective bonding conductor to the water pipe will involve a certain amount of floor ripping up, in order to increase its' csa. I don't think surface mounting will be an option somehow.

The upper lighting circuit could be properly fixed, as I believe all the connections are probably accessible in the loft space.

With the lower lighting circuit ,whilst polarity can be sorted with an accompanying note on the EIC, Carl what do you mean by 'if the wiring is done a certain way'? The method you describe using DP switches, or excessive cable length (inter-conductor capacitance), routing etc?
 26 February 2010 11:09 AM
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AJJewsbury

Posts: 11547
Joined: 13 August 2003

low energy lights would continually flicker when supposedly off.

A common problem - often due to the capacitance between L and SL on switch drops allowing a small current to flow when switches off - enough to keep charging the electronics in the base of the CFL and produce a quick 'flash' once enough charge has accumulated. The longer the switch drops, the more likely the problem - 2-way switching almost inevitably means longer drops and so higher capacitance - especially if the "modern" method of using 3&E between switches is used.

A quick search of the forum for "flickering" should turn up a few threads on the subject.

- Andy.
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