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Topic Title: Tripping Stype RCD
Topic Summary: 100mA S type trips 30mA doesn't
Created On: 01 May 2014 06:27 PM
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 01 May 2014 06:27 PM
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Avatar for Grobbyman.
Grobbyman

Posts: 320
Joined: 14 August 2005

New installation.

3 phase supply, lewden 100A 100mA S type 3 or 4 pole RCD.

Only one circuit connected to DB.

Via lewden 10A 30mA RCBO.

Lighting in 1.5 supplying 4 x Deluce non corrosive 2 x 27W LED units.

Switched in pairs.

Any one pair on OK.

Sorry meant to mention both incomer and RCBO tested OK no trips on 0.5 and 310ms on Stype at x1, 18.5x1 and 28.5x5 on RCBO.

Regards
George

Second pair switched in trips Stype incomer and not RCBO.

Any combination of 2 stays on any combination of 3 trips incomer.

New circuit, IR all 299Mohm, R1R2 0.42 and 0.54, Zs 0.64 and 0.76.

Any ideas?.
 01 May 2014 06:49 PM
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OMS

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What is the means of earthing ?

Have you tried a ramp test ?

Why type is the 100mA S RCD - ie AC or ?

Regards

OMS

-------------------------
Failure is always an option
 01 May 2014 07:07 PM
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Grobbyman

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Pmb so tns in my eyes.
AC type.
Sorry didn't get round to a ramp test.
Got fixated on why the 30mA wasn't going first.
Regards
George
 01 May 2014 07:08 PM
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Grobbyman

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Sorry, meant PNB so tns in my eyes.
AC type.
Sorry didn't get round to a ramp test.
Got fixated on why the 30mA wasn't going first.
Regards
George

Edited: 01 May 2014 at 07:17 PM by Grobbyman
 01 May 2014 07:19 PM
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OMS

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OK - just be aware that devices in accordance with BS EN 61008 of 100mA S type and 30mA do actually have a very small overlap

The 100mA Type S tripping characteristic will overlap the 30mA device in a region of around 40 - 80mA and in the time window between 130 and 180mS.

So you really need to do a ramp test to see what each device is doing.

Other than that, the numbers look OK, so you may just have a duff RCD - have you tried shorting the 100mA device to see if the problem influences the 30mA RCBO (which I assume is single pole)

I'd be suprised if you could get enough inrush current or leakage from 4 LED luminaires to be a problem, but worth checking leakage currents in addition to the functional test above.

Regards

OMS

-------------------------
Failure is always an option
 01 May 2014 07:25 PM
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Grobbyman

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OK thanks OMS.
Back in the morning so I'll go from there.
Thanks again.

Regards
George
 01 May 2014 08:11 PM
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AJJewsbury

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With electronic load, I wonder if there's a d.c. component to the leakage. If both the RCBO and RCCB are AC types then neither are guaranteed to trip out on leakage with a d.c. component - but that's not a guarantee that they won't either. I wonder if the 100mA unit is 'noticing' more of the d.c. component than the RCBO is....

Just 4 fitting tripping out a 100mA unit feels a bit dodgy anyway. No possibility of a N-PE fault somewhere?

- Andy.
 01 May 2014 08:16 PM
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Grobbyman

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Don't think so Andy.
Only Cct connected.
All IR reading over 299Mohms.
Regards
George
 01 May 2014 11:44 PM
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mapj1

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little worried you say "three or four pole" RCD - as the lamps are single phase (and so I presume is the 30mA trip) it is essential that the neutral current goes back through the three phase RCD too and cancels the total phase current - or it will see an imbalance and quite correctly operate. I assume you meant is 4 pole sensing. Is it possible that either the bit of neutral line between the two RCDs is actually earthed, or that the incomer RCD is wired up so that it is not really neutral sensing properly. (or less likely neutral sensing correctly but not live sensing on an offending phase.)
If you have a clamp-on meter you can confirm the equality or otherwise of L and N currents as seen at the in an out leads of the two RCDs.
worth a quick check anyway.
regards
M

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

Edited: 01 May 2014 at 11:51 PM by mapj1
 02 May 2014 06:05 AM
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Grobbyman

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No wired as 4 pole and all neutrals OK.

Regards
George
 02 May 2014 09:10 AM
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Grobbyman

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Here are the figures.
S type ramp 65mA.
Rcbo ramp 25mA
Lights each pair draw 0.45A with 0.5mA leakage.
Changed S type for main switch.
Rcbo does not trip.
Ramp still 0.25mA.
Current draw with both lamp sets on 0.88A
Leakage 1.1mA.
New S type on the way.
Regarded
George
 02 May 2014 10:47 AM
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Grobbyman

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Same fault second unit.
Must be fittings.
Connected socket circuit on 20A rcbo.
Running chargers and tools and not tripping s type.
George
 02 May 2014 03:20 PM
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mapj1

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Assuming no mistakes, then the only way this can make sense is if there is a leakage from the LED fittings that does not show on your meter (well only as 1,1mA ), but still upsets the type S.
It could be very short duration high amplitude pulses if the LED units are using fast switching supplies internally. (If the meter and RCBO are measuring average but the S-type responds to the peaks, they could all be in spec.)
Its a bit of a long shot and if so, its a bit poor really, and I'd expect the lamp fittings to fail the EMC requirements for CE marking if so. Assuming you have no more sophisticated test kit you could try bringing a longwave radio along side the fitting and listenging for nasty noises to test this theory.
If it turns out this is the case it may be that some kind of RF filtering is needed to keep the interference in the light fittings from getting out, but its not nice to have to do that - if designed well such filtering should be on the inside already. Are they a well known brand?
Some makers are more helpful than others- it may be worth a call to see if they have a technical bod.
regards M

edited for appalling taprotting

-------------------------
regards Mike
 02 May 2014 04:03 PM
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weirdbeard

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Originally posted by: Grobbyman
PNB so tns in my eyes.



What's the purpose of the 100ma TD RCD?
 06 May 2014 01:49 PM
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AJJewsbury

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What's the purpose of the 100ma TD RCD?

705.411.1 (iii) perhaps? I'm guessing, but PNB = single consumer Tx - therefore rural. Multiple 'non corrosive' fittings - doesn't sound domestic - so rural, non-domestic, so a farm at 1st guess (I could be wrong of course ... I usually am).
- Andy.
 06 May 2014 03:34 PM
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Grobbyman

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On the nose, Andy.
New chemical dosing unit.
Sorry been away for the Bank Holiday.
Waiting to hear from Deluce, probably in vain.

Regards
George
 07 May 2014 10:28 AM
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Avatar for KFH.
KFH

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I had exactly the same problem with a HF fluorescent tripping a 100mA S type (single phase) but not the local 30mA RCD. Turned out to be a faulty S type that did not like the transients from the fluorescent. Having fininsed after much testing and another visit with new RCD, everything working and demonstrated to customers wife, the customer phones me that night to say the fluorescent that was tripping the RCD did not work. 40 mile round trip to replace, the HF driver was faulty.
 08 May 2014 05:55 PM
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weirdbeard

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So it's a chemical dosing unit on a farm? .... and so far the lights and socket circuits are on RCBOs? .... I'm still wondering what the 100mA TD RCD's purpose is??
 08 May 2014 06:05 PM
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OMS

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Well 705.411.1 (iii) might be one reason

705.422.7 might be another

Regards

OMS

-------------------------
Failure is always an option
 08 May 2014 06:29 PM
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weirdbeard

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Originally posted by: OMS

Well 705.411.1 (iii) might be one reason



705.422.7 might be another



The RCBOs mentioned seem to cover those requirements with the info provided by the OP so far......
IET » Wiring and the regulations » Tripping Stype RCD

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