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Topic Title: MK RCBOs AND RCDs
Topic Summary: Interesting facts.
Created On: 21 March 2013 04:36 PM
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 21 March 2013 04:36 PM
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John Peckham

Posts: 7253
Joined: 23 April 2005

I have 70 warden controlled flats to test at the moment. I tested these 5 years ago and all the defects found then have been rectified with MK Sentry boards fitted to each flat. One 6A RCBO for the lighting and a 63A RCD protecting the sockets, cooker and door bell Tx.

I have so far I&Ted 32 flats.

2 out of 32 63A RCDs have failed not even tripping on the test button and not on a meter test.

Out of 32 RCBOs 23 have tripped on X5 at 10.2ms. which I thought was interesting*. I am used to getting very consistent readings on Merln RCBOs but surprised by MK.

* So interesting that I nearly spilled my Ovaltine from my tartan flask all over my beige anorak but luckily it went on my purple flares.

I will let you know how I get on when I have test all the other flats.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 21 March 2013 04:50 PM
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AJJewsbury

Posts: 10964
Joined: 13 August 2003

2 out of 32 63A RCDs have failed not even tripping on the test button and not on a meter test.

Not really a statistically significant sample size, so we should be careful of drawing too many conclusions - but 2/32 is 6.25% - which seems remarkably close to the 7% failure rate we were told about some years ago - slightly better even!

perhaps I'll get around to pressing the T button at home tonight....

- Andy.
 21 March 2013 04:56 PM
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Jobbo

Posts: 904
Joined: 08 July 2010

John

What did the results of the EICs say, for the remedial works undertaken?

One of our calibrated robin test sets has the same test results for 1x and 5x RCD tests, regardless of make or model. Think it's a 1620 model.

Perhaps I'll press my 'T' button too
 21 March 2013 05:19 PM
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BrucieBonus

Posts: 621
Joined: 20 February 2007

I bet you your tartan flares (or was it your corduory flask..?) that the test button has never been pressed since you were last there

Do you think this could affect it?
 21 March 2013 05:30 PM
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John Peckham

Posts: 7253
Joined: 23 April 2005

Andy

Yes a small sample size so of no great statistical value. When I have done 70 flats it may be a better indicator.

Jobbo

The EICs are on site so I may have a wade through the pile just to see what was recorded before. i am getting variations on my meter and it is calibrated and OK on the my test box.

Brucie

The RCDs were not there last time I PIRed the premises.. New consumer units fitted directly after. Yes I very much doubt if the test buttons have been pressed in the last 5 years. Any way it's a tartan flask and corduroys are only worn at weekends in the country!

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 21 March 2013 05:39 PM
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dbullard

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Joined: 02 March 2006

John, Dopke manufacture the MK range, I had a problem with some MK ones a few years ago and since have stopped using them due to the poor quality of the MK boards.

I had noticed that some of the ones that I had tested the tripping times between x1 and x5 were milli seconds apart at times or if from the same "batch" for instance 19.8 and 19.0 for the x1 and x5 respectively, and virtualy the same on the reverse test.

Regards

Daren

-------------------------
..... Dont pee in my pocket and tell me its raining ......


www.quest-electrical-sw.co.uk
 21 March 2013 05:47 PM
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OMS

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Personally, I wouldn't put any mileage into the idea that somehow a x5 test should achieve a faster disconnection than a x1 test in the sense that more current means faster disconnection - all you would expect is to be less than 40mS and 300mS respectively - that fact that they are much "closer" or quicker at x1 than expected isn't relevant

regards

OMS

-------------------------
Failure is always an option
 21 March 2013 06:59 PM
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dbullard

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Point noted OMS,

I am only concerned as you pointed out that they trip within the specified times allowed by BS 7671.

I usually have more Hagar failures per year than any other manufacturer, usually on average it is around 10 Hagar failures to any other, even though pretesting button pressing never helps in many cases

Regards

Daren

-------------------------
..... Dont pee in my pocket and tell me its raining ......


www.quest-electrical-sw.co.uk
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