Testing BS4293 S type RCD's

[securespark]

Some time ago, I posted here about this topic. I am still trying to get a definitive answer from somebody - ANYBODY - in the trade (NIC, ECA, IEE, Manufacturers etc....)

Has anybody got the same problem??

 

[Jim2287]

What is the problem ?

 

[Spark123]

How do you find out what the rated time delay is on a BS4293 time delay RCD?
BSEN61008/9 Type S RCDs should trip within 130mS to 500mS.

 

[plugwash]

reading the standard would be one way though unfortunately you may have to pay to get hold of it.

 

[Jim2287]

http://www.iee.org/Publish/WireRegs...iring_matters_inspection_and_testing_rcds.pdf


page 3 of 5... says 4293 was replaced by 61008, so should be same as requirements for 61008 S type but ...

page 5 of 5 gives the actual trip times required

 

[Spark123]

It only gives 50% of rated trip time + 200mS to 100% of rated trip time +200mS for a BS4293 though, how do you find out the rated trip time?
BS4293 has been superseded but is still current afaik.

 

[Jim2287]

doesnt the RCD say a rated time delay on it ?

if not... god knows

 

[Spark123]

If it's any concellation I thought they'd say on them too, but being a factory spark have not come across any of them. I believe the Wylex ones are 0.5s delay but that is only hearsay!!

 

[ebee]

The BS ones are within 200mS for non delayed
and
within 50% to 100% of this plus a further 200mS for delayed = 300 to 400mS

BS (EN) are within 300mS non delayed
and 130 to 500 mS delayed

 

[Jim2287]

ye thats what i thought, but its not how it reads on that table
and then i thought, why not just write 300-400 if its not different for other ratings of RCD ?

 

[ebee]

Yes it could`ave been written a little clearer perhaps.

I think the BS spec was better than the BS(EN) version for two reasons:-

1/ Within 200mS not 300mS for non delayed being one reason.

2/ Delayed being 300mS to 400mS allows better chance discrimination over a downstream 200mS device than a 130mS to 500mS might do over a 300mS device being another reason.

Furthermore a factor of three of the tripping current should also be provided for discrimination ie :-

usually a delayed 100mA feeding a non delayed 30mA trip

or ,

in theory anyway (if you can get them) a delayed 30mA feeding a non delayed 10mA trip

 

[Jim2287]

the factor of 3 ... is that why we use 100mA time delayed on TT ?

something strange we found recently .. Contactum dont make time delay RCDs

is time delay a requirement on TT or is it just better practice to have one? ... to prevent lighting circuits going down (this would be a hazard to consumer)

 

[ebee]

Time delay AND factor of 3 gives (should give) a decent discrimination if one RCD is feeding the other for TT giving 100mA time delay for all circuits to compensate of the relatively poor earth connection of earth rods and and then giving additional 30mA non delayed for sockets say.

Another alternative is to use two seperate RCDs and therefore can be non delayed because one is not feeding the other, but you need one (non RCD) main switch feeding them both.

Either option then will give one main switch for the whole installation.

 

[securespark]

Yes, that's the problem. I'm trying to prepare a presentation on testing RCD's, but without knowing the TD's, I cannot say what the pass/fail point is.

How does anybody else here tell if a BS4293 TD RCD has passed or failed??

Nobody can tell me what their BS4293 time delays are. Only one I have come across is labelled with the TD.

Square D - it said Time Delay 60ms.