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Topic Title: Time delayed 100mA rcd testing
Topic Summary: How do you test them?
Created On: 31 July 2011 08:36 PM
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 31 July 2011 08:36 PM
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deleted_1_infinity2011

Posts: 120
Joined: 12 March 2011

Hi please could i borrow some expertise...

Was testing a house today, TT system, 100mA S type time delayed 100A main switch.

How do you test these to check required tripping times are correct?

Obviously with a normal rcd test it fails as its a time delayed device so how can i check it meets the rquired trip times?

Thanks

D
 31 July 2011 08:43 PM
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KFH

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You test it the same as a normal RCD with a 100mA setting on the tester and the test time should be displayed. I don't have my notes with me and I cannot remember the times required for the different BSEn types but around 200-300mS. If it is fitted in the CU then you will have to test at the output terminals. Amended - Except you do not test at 5 times rating.
 31 July 2011 08:47 PM
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deleted_1_infinity2011

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Thanks i thought that was the case, i got about 210 mS on 1x and obviously 5x will not operate within 40mS so tester does not like it.
Dont suppose you know where the times for time delayed devices are?

Thanks!
 31 July 2011 08:51 PM
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sparkingchip

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5 x 100mA is 500mA too much to inject into the installation without risking impairing safety

Andy
 31 July 2011 09:37 PM
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KFH

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BSEN 61008 should trip in 130- 500mS. Don't have any others to hand. I thought they were in the regs and the OSG.
 31 July 2011 09:50 PM
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ebee

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Daft thing is that with the BS (EN) spec as opposed to or old BS spec then the time delayed one might have a shorter trip time than a non delayed type and both devices still be within spec

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Ebee (M I S P N)

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 31 July 2011 10:13 PM
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jsa986

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What test meter do you have? it will probably display a "s" on the LCD readout when you have it time delay mode. Then it counts down from 5s on the Megar mft

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 01 August 2011 07:38 AM
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spinlondon

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In the current Regulations, the maximum time allowed is 1s, in the 16th the time was 5s.
The tripping current should be no greater than 5x the rated operating current.
As such a 100mA RCD should trip within 1s (5s for 16th) at a test current no greater than 500mA.
 01 August 2011 09:13 PM
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deleted_1_infinity2011

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Thanks all,

I have a megger 1553 cant find a time delay option though!
 01 August 2011 09:24 PM
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spinlondon

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When you scroll through the options, you should be able to switch between G and S. G being General, and S being time delayed.
 01 August 2011 09:37 PM
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hifly

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Originally posted by: jsa986

What test meter do you have? it will probably display a "s" on the LCD readout when you have it time delay mode. Then it counts down from 5s on the Megar mft


I think my fluke counts down for 30 sec's

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 01 August 2011 10:44 PM
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deleted_1_infinity2011

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I never knew that! il be checking it out first thing though thanks!
 02 August 2011 12:08 AM
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jsa986

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Vince, thinking about it, I think your right, it counts from 30s, don't know where I got 5s from??? Either way there is a numerical countdown ha.

Don't come across them very often anymore...thats my excuse ;-)

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 04 August 2011 11:33 PM
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AJJewsbury

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The tripping current should be no greater than 5x the rated operating current.

The 5x current is only a requirement for 30mA RCDs used for additional protection (tripping time <=40ms). All RCDs should trip at 1x (although perhaps more slowly) but not trip at all below 0.5x.
- Andy.
 05 August 2011 07:40 AM
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ebee

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AJJ,
shouldn't 10mA RCDs (if used for personal protection) also operate at 5 x (= 50mA) in 40ms or less?

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Ebee (M I S P N)

Knotted cables cause Lumpy Lektrik
 05 August 2011 08:20 AM
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GeoffBlackwell

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Take a look at Table A3 in Appendix 3.

Regards

Geoff Blackwell
 05 August 2011 09:22 AM
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ebee

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The bit that gets me is that it is theoretically possible for a time delayed RCD to trip before a non delayed type if used in cascade

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Ebee (M I S P N)

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 05 August 2011 10:17 AM
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Legh

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I see quite a lot of the BS4293 100mA S front end RCDs
That makes it interesting when using the modern multi-function testers.

Legh

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 05 August 2011 06:01 PM
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sparkingchip

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Why does the tester count down from 30s to test a 100mA S-type RCD?

Andy
 05 August 2011 11:36 PM
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sparkingchip

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electrical.theiet.org/wiring-matters/15/insp-test-rcd.cfm?type=pdf
IET » Wiring and the regulations » Time delayed 100mA rcd testing

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