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Topic Title: Have I gone mad or did i just hear that right ? No plastic fuseboards.
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Created On: 01 October 2014 03:20 PM
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 28 February 2015 01:02 PM
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sparkingchip

Posts: 9953
Joined: 18 January 2003

I had a knee trembling moment yesterday as my legs wanted to turn on their heels and run.

Down in the cellar of a HMO I needed to isolate the cooker circuit and the thought went through my head "I wonder when the RCD test buttons were pressed?"

I pressed the RCD without incident then moved to the first of four RCBOs.

I pressed the RCBO test button and it buzzed, then there was a bang, smoke and the smell of charring plastic followed by more buzzing another bang more smoke and a even stronger smell of burning plastic.

This is it I thought as I threw the main switch, I'm actually going to see a plastic consumer unit go up in flames in front of me whilst I'm in a dark windowless cellar by myself, I retreated to the bottom of the stairs ready to sprint as best I can to the van and back to get my dry powder extinguisher.

I waited a short time and as nothing erupted I then removed the RCBO from the CU to find it had contained the arc.

I put the whole incident down to lack a lack of regular RCD testing with no one doing it in the last two and a half years since I last did it.

It does make the old knees tremble though!

Andy
 28 February 2015 10:38 PM
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napitprofessional

Posts: 452
Joined: 08 March 2008

At least it blew up whilst YOU were pressing the button - electricians have no value in the industry so no great loss!

If a member of the public is hurt or killed that`s another matter - mind you, Emma Shaw (22) was unlawfully killed in 2007 and exactly the same practices continue to this day ....

-------------------------
B. Eng (Hons) MIET
 28 February 2015 10:51 PM
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leckie

Posts: 4317
Joined: 21 November 2008

Now that is a thought! We'd encourage customers to press the test button. Andy did it and nearly got fried.

I remember doing an RCD test a few months back as part of an EICR. The rcd passed the meter tests, so I pressed the test button. The RCD went bang and a hole burnt through the front of the device.

Maybe it's not as safe as we thought to press the button!
 01 March 2015 04:23 AM
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GeoffBlackwell

Posts: 3793
Joined: 18 January 2003

There have been product recalls concerning this problem - the bang can be quite impressive .

Regards

Geoff Blackwell
 01 March 2015 10:33 AM
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mapj1

Posts: 9346
Joined: 22 July 2004

The test button puts a resistor across the outgoing live to incoming neutral to create an imbalance, but to keep the size down, the resistor is small and only rated to handle the mains for a very short duration. IF the breaker doesn't open fast enough, the resistor catches fire, which is a disappointing design weakness.
The use of a thermally fused resistor, or a higher wattage one, both are standard parts, would have added a few pence to the bill of materials, so obviously was not done in some cases.

-------------------------
regards Mike
 01 March 2015 12:01 PM
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mistercohen

Posts: 30
Joined: 28 October 2011

Is it possible that the increase in fires within CU's within recent years could be explained by the increase in the number of high current joints within the CU's.
Imposed by the requirements of the regulations to add more RCD's and to split the installation up into chunks.

Yes each chunk has a lower current than the main switch.

100 amp DP incomer CU had typically 5 high current joints the split load CU could have 10 and the high integ 3 way split load could have 14 all depends on where and how much power hungry equipment is connected.
From my time at college many years ago I remember calculation MTBF and MTTF and every joint and every component added decreases the Mean Time To Failure and Mean Time Between Failures.
Also the increase of current hungry loads such as showers going from 7kW toward 12kW.

I do also want to add my voice to the chorus singing out against the registration bodies (and the fiasco that is part P) that have proliferated whilst the standard of workmanship and depth of knowledge, in my opinion has fallen.
Not generally noticable on this forum I might add
 01 March 2015 07:14 PM
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Zoro

Posts: 300
Joined: 31 July 2011

There is nothing wrong with Plastic Consumer units that are compliant with BS/EN 60439-3 or BS/EN61439, they do not burst into flames, they are safe,independent testing has proved this.

Certain Manufacturers are blaming ALL plastic consumer units and stating that CU's should be steel, in an attempt to cover up the fact that they did not bother to make them non combustible as required in the BS/EN standard.

Obviously there are millions of these things that should be recalled, changes to Equipment Specifications should not be made in Installation regulations.

This has only been done, because the bodies that set Equipment Regulations would never agree to the changes now in BS7671, as there is nothing wrong with the specification of BS/EN 60439-3 and BS/EN61439-3.


This is verging on fraud.
.
 02 March 2015 10:20 AM
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napitprofessional

Posts: 452
Joined: 08 March 2008

Originally posted by: Zoro

There is nothing wrong with Plastic Consumer units that are compliant with BS/EN 60439-3 or BS/EN61439, they do not burst into flames, they are safe,independent testing has proved this.



Certain Manufacturers are blaming ALL plastic consumer units and stating that CU's should be steel, in an attempt to cover up the fact that they did not bother to make them non combustible as required in the BS/EN standard.



Obviously there are millions of these things that should be recalled, changes to Equipment Specifications should not be made in Installation regulations.



This has only been done, because the bodies that set Equipment Regulations would never agree to the changes now in BS7671, as there is nothing wrong with the specification of BS/EN 60439-3 and BS/EN61439-3.





This is verging on fraud.

.



Verging on fraid?

Most definitely - but from which side of the legal fence?

How on earth can a consumer unit enclosure be "certified" as compliant with a standard yet fail (spectacularly) when tested independently?

Both Electrical Safety First and BEAMA appear to have stated that poor workmanship is causing the "loose connections" within the consumer units - yet some manufacturers only refer to loose connections as the root-cause of the fires ....

Interesting that, in the consumer electrical sector, recalls have been initiated for far,far less .... perhaps it would be appropriate for Electrical Safety First to comment as they are desperate to take on the role of product recall champions?

I am sure that the fact that both ESF and BEAMA are industry funded in no way causes any conflict of interest.

-------------------------
B. Eng (Hons) MIET

Edited: 02 March 2015 at 10:34 AM by napitprofessional
 10 January 2016 04:57 PM
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jonnyblagwind

Posts: 1
Joined: 10 January 2016

did we ever get to the bottom of what to rate a plastic CU in a EICR? i saw some people saying C1 earlier i'd say its more a C2 though as a danger under fault conditons ie:bad termination
 10 January 2016 05:37 PM
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daveparry1

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Doesn't comply with current regs. is the worst it could be given in my view?
 10 January 2016 05:42 PM
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Spark68

Posts: 26
Joined: 20 April 2012

Originally posted by: daveparry1

Doesn't comply with current regs. is the worst it could be given in my view?


That was my understanding too Dave, C3 seeing as they still complied until Jan 1st 2016.
 10 January 2016 05:48 PM
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leckie

Posts: 4317
Joined: 21 November 2008

This article goes through most scenarios, including codes if required under certain circumstances
http://professional-electricia...-mythbust-amendment-3/
 10 January 2016 06:00 PM
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Spark68

Posts: 26
Joined: 20 April 2012

Cheers Leckie, I had already seen that link
 10 January 2016 07:40 PM
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GLMelectrical

Posts: 71
Joined: 05 January 2016

Originally posted by: jonnyblagwind

did we ever get to the bottom of what to rate a plastic CU in a EICR? i saw some people saying C1 earlier i'd say its more a C2 though as a danger under fault conditons ie:bad termination


its a 3

poor terminations identified would be a 2

its a bit like the no RCD for portable equipment thing isn`t it...say you have a 3036 board..and it complied when it went in (times, barriers & enclosures etc)...but theres no RCD for finals....you could fail...say the downstairs sockets final circuit for lack of RCD for additional protection....but not the board...(the solution in this case would be to fit an RCD socket outlet for an outlet identified as being used for portable/outdoor equipment)

but I digress
 10 January 2016 09:21 PM
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leckie

Posts: 4317
Joined: 21 November 2008

It is probably no code and just a comment in the majority of circumstances. I posted a link to Hagers take on this. NICEIC,ECA, etc, take the same view, so its probably worth reading the article before jumping to conclusions.
 11 January 2016 09:13 AM
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Zoomup

Posts: 3265
Joined: 20 February 2014

Originally posted by: sparkingchip

I had a knee trembling moment yesterday as my legs wanted to turn on their heels and run.



Down in the cellar of a HMO I needed to isolate the cooker circuit and the thought went through my head "I wonder when the RCD test buttons were pressed?"



I pressed the RCD without incident then moved to the first of four RCBOs.



I pressed the RCBO test button and it buzzed, then there was a bang, smoke and the smell of charring plastic followed by more buzzing another bang more smoke and a even stronger smell of burning plastic.



This is it I thought as I threw the main switch, I'm actually going to see a plastic consumer unit go up in flames in front of me whilst I'm in a dark windowless cellar by myself, I retreated to the bottom of the stairs ready to sprint as best I can to the van and back to get my dry powder extinguisher.



I waited a short time and as nothing erupted I then removed the RCBO from the CU to find it had contained the arc.



I put the whole incident down to lack a lack of regular RCD testing with no one doing it in the last two and a half years since I last did it.



It does make the old knees tremble though!



Andy


Hello Andy,
I had a brand new Newlec out of the box R.C.B.O. do exactly what yours did. It must have been the test resistor overheating and blowing up as the device did not open its contacts. I will now only connect R.C.D.s and R.C.B.O.s in series, (different makes) especially on TT systems as I no longer trust just one device to operate effectively.

It is VERY worrying. More of China's best no doubt.

Z.
 11 January 2016 11:43 AM
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potential

Posts: 1630
Joined: 01 February 2007

....and if old and new RCBOs and RCDs are going bang when the button is pushed, is it reasonable to demand that the householder regularly tests them?
 11 January 2016 02:27 PM
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mapj1

Posts: 9346
Joined: 22 July 2004

"IMPORTANT - This installation, or part of it, is protected by a very badly made device which sometimes flies off the wall if an earth fault develops. Test quarterly by pressing the button marked 'T' or 'Test'. The device should switch off, probably, or blow up, and should then be switched on or replaced to restore the supply. If the device does not either switch off the supply or blow up when the button is pressed, seek expert advice.

Oh yes, MORE IMPORTANT Wear Suitable PPE to perform this test."





Does it really need a product standard to insist on safe self-fusing test resistors - they are soo expensive after all.

10p is about twice the price of the non self fusing, flammable kind beloved of the RCD makers
edited to fix link to right sort of resistor TE RR series 4700 ohms..

Sigh, until then more stuff to live in the understairs cupboard and get removed every time the meter man comes.


-------------------------
regards Mike


Edited: 11 January 2016 at 02:41 PM by mapj1
 11 January 2016 07:03 PM
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GLMelectrical

Posts: 71
Joined: 05 January 2016

Originally posted by: potential

....and if old and new RCBOs and RCDs are going bang when the button is pushed, is it reasonable to demand that the householder regularly tests them?
well....if its wong chong RCDs/RCBOs going pop...then its a switchgear issue....not plastic enclosures

the same could be said of poor/soft terminals...
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