RCBO tripping time

[safesinbad]

I've just installed an outside supply using 10mm 3core swa cable supplied by a 32A 30mA RCBO. Trips at around 12ms on 1x (cant remember exact reading), 27mA on ramp and >40ms on 5x which does not comply. The run of the supply cable is about 40-50 metres. I have tried 3 different RCBO's on the circuit and still nothing on 5x test. They work fine when i tested them with the ring main. The outside supply cable insulation resistance was also ok (>299Mohm) and the Zs was ok. Any ideas????

 

[spark1]

Which end of the circuit did you test at ?

 

[ericmark]

It seems wrong way around at X1 it could be expected to be over 40ms and at X5 passing but not other way around. Assuming lower of + and - reading in both cases only conclusion is fault with tester.

Have you tried testing another RCD to compare reading?

 

[Spark123]

You should always test an RCD in isolation - things like connected equipment and the capacitance of the cable can effect the reading given on your tester.

 

[safesinbad]

RCD 1x should be less than 200ms this doesn't mean it should be greater than 40. I tested the circuit at the furthest point.

The tester works fine, recently calibrated.

 

[ColJack]

how long did you leave between the 1x test and the 5x test?
on a run that long it may take a while for the cables to "charge up" again with the capacitance.. ( I know it sounds daft but on long runs with an IR test it can take several seconds for the wires to "charge" with the reaging rising from a low megaohms to a high...

 

[JohnD]

but on the AC supply, cables don't charge up with capacitance

I find it difficult to grasp how the 5x was slower than the 1x. They will usually trip in less than 1 cycle of the supply, as the current increases to the tripping point. My MEM RCBOs are usually between 12 m/s to 25m/s at 1x, and about 12m/s at 5x

 

[Spark123]

RCD 1x should be less than 200ms this doesn't mean it should be greater than 40. I tested the circuit at the furthest point.

The tester works fine, recently calibrated.

300ms for a BS EN 61009 device.
200ms for an old 4293 type device.

 

[safesinbad]

RCD 1x should be less than 200ms this doesn't mean it should be greater than 40. I tested the circuit at the furthest point.

The tester works fine, recently calibrated.

300ms for a BS EN 61009 device.
200ms for an old 4293 type device.

since when is it 300ms, 17th ed? is 5x still 40ms?

 

[spark1]

Test at the RCBO itself and with load isolated

 

[JohnD]

And to be fair, they are manufactured to trip far faster than the minimum acceptable limit.

 

[Spark123]

RCD 1x should be less than 200ms this doesn't mean it should be greater than 40. I tested the circuit at the furthest point.

The tester works fine, recently calibrated.

300ms for a BS EN 61009 device.
200ms for an old 4293 type device.

since when is it 300ms, 17th ed? is 5x still 40ms?

The maximum required speed of the 1X test is dependent on the British or European standard which it is manufactured to.
The max speed of the 5X test is still 40ms regardless.
Have a peep in GN3 on the RCD testing section if you have a copy.