RCD with variable ms an mA settings

[Bradley6969]

Hi, been looking at variable RCDs as came across one at a job, settings range from 30mA to 3 Amps and ms from no delay to 3 second delay can someone explain please? As if I come to test my tester only goes up to 1000mA also some I’ve seen are set on like 0.5 seconds which isn’t an RCD meant to trip within 500ms? Thanks

 

[Marvo]

Variable time and residual current setting allow for horizontal and vertical discrimination when more than one RCD is installed. Also with commercial and industrial application there might be a need to strike a balance between how critical a circuit is and what level of user safety is provided.

Discrimination

 

[snowhead]

also some I’ve seen are set on like 0.5 seconds which isn’t an RCD meant to trip within 500ms?

Have a think about that one and if thinking doesn't sort it, then Google will.

 

[DPG]

I'm sure you asked this same question before about RCD times in mS and seconds. If you check how many milliseconds are in a Second you will see the answer to your question.

 

[Taylortwocities]

Marvo, absolutely. And thank you for that link. Discrimination between RCDs is something I keep banging on about (I had an arguement with my lecturer at college about this when I did the 236, quite a while ago).

In fact, discrimination between current-limiting devices is a technique that is not taught or understood (or ignored) any more. So many times I see an external circuit coming off a 13A FCU, fed into a "garage" CU and the sockets cabled as a ring final and "protected" by a 32amp MCB. Pointless.

But its a rainy morning and I'm feeling maudling.
Where's that Jack Daniels....

 

[Bradley6969]

So I’ve come to a factory, it’s set at 500mA with a time delay of 0.5 seconds, my tester only allows up to 500ms I can’t say it’s failed when it’s set above my tester limits? All I can do is test with no time delay then add that to the time delay it was set to so I’m at a lost cause? Or do I test with no delay put NA in RCD X1 box but tick RCD to say it’s operating?
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Have a think about that one and if thinking doesn't sort it, then Google will.

He doesn’t help I need to understand
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I'm sure you asked this same question before about RCD times in mS and seconds. If you check how many milliseconds are in a Second you will see the answer to your question.

Yes but I don’t understand what to put
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Variable time and residual current setting allow for horizontal and vertical discrimination when more than one RCD is installed. Also with commercial and industrial application there might be a need to strike a balance between how critical a circuit is and what level of user safety is provided.

Discrimination

Thanks, I don’t understand how they should be tested at more than 0.5 seconds delay as my tester will only test upto 500ms? That’s if the RCD is tripping greater than 500ms

 

[DPG]

Sorry, I may have misunderstood the question.

 

[Bradley6969]

Sorry, I may have misunderstood the question.

Ok no worries

 

[Wilko]

Hi - if that delay is adjustable, perhaps temporarily set it at a few lower delays confirm it trips as expected. The 500ms setting would remain unverified, but its likely to work. Record your all test values.

 

[Bradley6969]

Hi - if that delay is adjustable, perhaps temporarily set it at a few lower delays confirm it trips as expected. The 500ms setting would remain unverified, but its likely to work. Record your all test values.

Thanks, and yes that’s what I’ve done is tested with no delay so I’m basically just testing at 500mA with no delay, I just wanted to see what else people do as I can’t verify at 500mA with a delay of 0.5 seconds and for instance I got 100ms with no delay if I add that to my 0.5 delay which means 600ms but I can’t prove it will trip at that, I’ve looked at manafacturs instructions and they say a threshold of 20 percent so 600ms would be acceptable all I’m going to do is NA the RCD trip time and tick the box then note in comments
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I take it there are testers out there which will let you test higher than 500ms? Unfortunately my Martindale doesn’t

 

[snowhead]

If the RCD settings are outside the range of your tester then you will need an (very expensive) alternative tester that does cover the range.

As Wilko has said you could alter the settings to your testers max, but that doesn't guarantee that the RCD will work as originally set.

 

[Bradley6969]

If the RCD settings are outside the range of your tester then you will need an (very expensive) alternative tester that does cover the range.

As Wilko has said you could alter the settings to your testers max, but that doesn't guarantee that the RCD will work as originally set.

I have done my testers max is 500ms as it’s a time delayed RCD, and yes in all honesty it’s only protecting another panel which has the same RCD just set to achieve selectivity for all outgoing circuits thanks for your help I just wanted to see what people do in a similar situation

 

[Bradley6969]

Hi, someone at work saying my tester should test above 500ms am I right in saying that it doesn’t

 

[David Prosser]

Don't you set the current then meter times and displays how long it takes to trip ?

I think my Megger times out at 2s or 2000ms. If you set your tester to "no-trip" 50% it should then tell you what time your meter will run to.

 

[Bradley6969]

Don't you set the current then meter times and displays how long it takes to trip ?

I think my Megger times out at 2s or 2000ms. If you set your tester to "no-trip" 50% it should then tel you what time your meter will run to.

Yes I do, maybe I haven’t notice, but what I usually do is set to what ever mA eg 500mA and if time delayed then you switch to (S) but looking at it my tester actually tests to 2000ms on half times so I may have found my problem?
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I just didn’t think it will trip half times so never tried?