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Topic Title: EVERY DAY A SCHOOL DAY
Topic Summary: Self Testing RCDs
Created On: 15 May 2013 10:31 PM
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 15 May 2013 10:31 PM
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John Peckham

Posts: 7371
Joined: 23 April 2005

I am teaching the 2394 course at the moment and last night I did a session on RCDs and how to test them. Tonight one of my students brought in to college (show and tell) a self testing RCD. He is fitting these at the moment to street comms. cabinets. The RCD self tests and re-sets every 90 days. It also will re-set after tripping after a set pause period.

I have heard of self re-setting RCDs and seen pictures of them but I had not heard or seen a self testing RCD.

The device has a small metal lever under the operating toggle handle that powers the device to the on position after the self test or a nuisance trip. If the RCD does not re-set a signal is sent by the comms. cabinet, it has standby batteries, to a remote station.

So whilst no doubt other forum members will no doubt say they are as common as muck it was something new for me.

Nice and cold and windy tonight so we went outside to play earth electrode resistance testing.

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John Peckham

http://www.astutetechnicalservices.co.uk/
 15 May 2013 10:43 PM
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peteTLM

Posts: 3119
Joined: 31 March 2005

just had a google on this and could only find one, and even that didnt have a picture of it. It also had only a mobile number as a contact, so not so sure about this one................

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Lack of planning on your part doesn't make it an emergency on mine....

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 15 May 2013 10:54 PM
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rocknroll

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Yes they been around for a while, generally known as 'auto resettable RCD's', you will find them appearing more and more in our on-street charging points, to protect against damaged or incorrectly wired leads and car sockets, tampering etc;

regards

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"Take nothing but a picture,
leave nothing but footprints!"
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"Oh! The drama of it all."
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"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
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 16 May 2013 05:56 AM
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ebee

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Well John,
I`m common, I`m muck but I never seen one.
Only heard them mentioned on here previously.

Can think of a few disadvantages though.

Horses for courses methinks.

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Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 16 May 2013 09:55 AM
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OMS

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Quite common on the big public lighting PFI's or DBFO's - it's the balance regarding safety and the fact the designer doesn't want the drunk leaning on the cabinet risk but the lender doesn't want the "non availability" risk.

It's a device deployed for a purpose - is it a good idea - in principle, yes - but it'll take a while yet before the wiring regs catch up with the cutting edge of worst practice, when these find themselves into the more general market.

Regards

OMS

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Failure is always an option
 16 May 2013 10:48 AM
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KFH

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I did a test on a plug in RCD and it flew through the automated tests, 1/2, *1, *5 at 0 and180 all with good trip times, the only problem being I had not reset it even once, it was resetting itself almost instantly every time, I even ran the tests again as I could not believe it. The customer, who was watching, binned it. Was I mistaken and it was in fact one of these new fangled auto resetting ones :-)
 16 May 2013 11:11 AM
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ebee

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PFI's or DBFO's

Agghhh.
Too many abbreviations!



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Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 16 May 2013 11:44 AM
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OMS

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Originally posted by: ebee

PFI's or DBFO's

Agghhh.

Too many abbreviations!

[IMG][/IMG]


Sorry

PFI - Private Finance Initiative

DFBO - Design, Finance, Build, Operate

The system I was involvd with is the Gewiss Auto Test with Restart

BS 7671 compliant - still not sure ?


Regards

OMS

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Failure is always an option

Edited: 16 May 2013 at 11:52 AM by OMS
 16 May 2013 12:02 PM
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ebee

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No problem.

Actually I guessed the PFI one.



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Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 16 May 2013 12:17 PM
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AJJewsbury

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BS 7671 compliant - still not sure ?

530.3.5 ?
- Andy.
 16 May 2013 02:03 PM
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AJJewsbury

Posts: 11268
Joined: 13 August 2003

Hifly posted this a while back: http://www.electric-works.co.uk/CAT06_011_CT_EN.pdf - might be of interest still.
- Andy.
 16 May 2013 04:59 PM
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OMS

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Originally posted by: AJJewsbury

BS 7671 compliant - still not sure ?


530.3.5 ?

- Andy.


Yes, I was comfortable that we met the requirements (or we wouldn't have specified it) - it just sat a little awkwardly on my shoulders, if you know what i mean - particularly with regard to 411.3.3 - something counter intuitive to it really

Regards

OMS

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Failure is always an option
 16 May 2013 05:03 PM
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Parsley

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I haven't had a chance to look at it this yet but the word automatic reclosure caught my eye.

http://newsletter.voltimum.co....f60dc78x12680935x1116

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 16 May 2013 05:41 PM
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AJJewsbury

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it just sat a little awkwardly on my shoulders

I know what you mean - something that's there to disconnect doing connecting....

But on the other hand, it's meant to test the circuit using max. 100uA before re-closure - which probably has the edge over the householder (or maintenance electrician) manually resetting the RCD without checking anything first. The self-test facility probably means it's more likely to open when required in the first place than a conventional RCCB too.

Maybe the question is: what's the effect on the human body of getting say 3 jolts in a row (say 40ms at a time, a few seconds apart) - is it the same as getting one 40ms jolt or does the effect accumulate, so it's (say) the same as one 120ms jolt?

- Andy.
 16 May 2013 06:09 PM
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OMS

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Originally posted by: AJJewsbury

it just sat a little awkwardly on my shoulders


I know what you mean - something that's there to disconnect doing connecting....

No problems with auto reclosers - they were common in my previous life - it's the small almost disposable nature of thes ethough - quality is most certainly an issue.

But on the other hand, it's meant to test the circuit using max. 100uA before re-closure - which probably has the edge over the householder (or maintenance electrician) manually resetting the RCD without checking anything first. The self-test facility probably means it's more likely to open when required in the first place than a conventional RCCB too.

Agreed - we convinced ourselves of that to be honest - it's just that slightly nagging doubt that persists


Maybe the question is: what's the effect on the human body of getting say 3 jolts in a row (say 40ms at a time, a few seconds apart) - is it the same as getting one 40ms jolt or does the effect accumulate, so it's (say) the same as one 120ms jolt?

I'd say the gap between was long enough for the effect (on fibrilation at least) not to be accumulative - more generally - I don't know - it's not something we generally consider is it.

Where's David Cockburn when you really need him


- Andy.


Regards

OMS

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Failure is always an option
 17 May 2013 09:11 PM
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GB

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I am not familiar with these self testing units so may need to do a little catch up next week but where does the test button causing actual mechanical operation of the device fit into this? as i thought it was the mechanical malfunction of the device after sitting for years on end in the same position which was a major issue, with testing of older units proving a high percentage would not operate under fault ie seized!!
or as I am now typing and thinking does the self test function actual cause the unit to trip and then the auto re-set comes into play.
Oh I need to catch up.....quick
 17 May 2013 10:17 PM
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John Peckham

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Joined: 23 April 2005

GB

Yes I have heard and seen information on auto resetting RCDs but the 90 day self test function was new to me. The device I saw was made by Gewiss and it auto trips every 90 days and then re-sets itself. The auto test facility is marked on the device as complying with BS7671.

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John Peckham

http://www.astutetechnicalservices.co.uk/
 19 May 2013 06:37 PM
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M.Joshi

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Joined: 10 January 2003

Whilst on the subject, thought I'd post this video I have watched before - someone's (dangerous) school project!

http://www.youtube.com/watch?v=jMesP5T4_bc

This comment below the video is very appropriate:

andk1987 - Lemme know how that auto reset feature goes when youre laid on the floor knocked out still in contact with a faulty appliance or otherwise and you continue to get shocked´╗┐ because you thought itd be a great idea to pretty much render the safety feature inoperable.


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M.I.E.T - Forfeited this due to The I.E.T's ridiculous membership rules!
 26 May 2013 07:50 PM
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andk1987

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Joined: 26 May 2013

Ha ha that was me..... someone showed it to us on a training course and i had to have a look when i got home.... muppets tho
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