Whats this mean on a rcd test

[newtothis]

There is a very good video here on YouTube., that explains testing at the CU. The bloke is a bit posh but a lot of his stuff is very good and he explains it all well.
http://youtu.be/ZaAUg75BR5Y

Yeah he's a bit posh alright, I've watched a lot of his stuff too- what makes me laugh is he calls RCDs - ArseyDs.:rolleyes2:

 

[Vitesse]

Yeah he's a bit posh alright, I've watched a lot of his stuff too- what makes me laugh is he calls RCDs - ArseyDs.:rolleyes2:

I think JW!!!!!! is a little eccentric but certainly knows his stuff. His videos on neon screwdrivers are proof on why you should never use them.

 

[newtothis]

Check out Steve Redpath of transeuroengineering - he's gotta be the undisputed king of the flat, monotone delivery.
https://youtu.be/NTZDrRSXtTA
I'm sure he's probably good lad though, it can't be easy presenting vids.

Hmmm just thinking out loud, all these YouTube blokes that are using the socket testers for testing RCDs
The common thing that links them is they're all testing boards with one RCD on them.
Would that make a difference ?

 

[Leesparkykent]

Check out Steve Redpath of transeuroengineering - he's gotta be the undisputed king of the flat, monotone delivery.
https://youtu.be/NTZDrRSXtTA
I'm sure he's probably good lad though, it can't be easy presenting vids.

Hmmm just thinking out loud, all these YouTube blokes that are using the socket testers for testing RCDs
The common thing that links them is they're all testing boards with one RCD on them.
Would that make a difference ?

I done my C&G 2399 with Steve redpath at trans euro. He knows his stuff.

 

[newtothis]

I done my C&G 2399 with Steve redpath at trans euro. He knows his stuff.

Ha ha it's a small world, good job I wasn't being too mean about him.
I watch a lot of yankee guitar learning vids, they tend to have a bit more razmataz about them.
I suppose lecky testing is a more serious topic, cos of the risk of death, and all that.

 

[Deleted member 26818]

Just to add my 2 cents worth.
Yes you can test RCDs at a socket.
However you are more likely to have a fail.
The resistance of the circuit conductors between the socket and the RCD will lower the amperage of the test current, which as we know is only milliamperes to begin with.
When testing RCD sockets, it usual to use the 3 pin plug lead, rather than probes.

 

[davesparks]

The resistance of the circuit conductors between the socket and the RCD will lower the amperage of the test current,

I love it, please can you expand on this a bit more and explain exactly how this works?

There's a chap called kirchoff who would love to hear all about it!

 

[Deleted member 26818]

I suggest you ask Kirchoff himself to explain.

 

[davesparks]

I suggest you ask Kirchoff himself to explain.

It was a joke, which you clearly didn't get!

The test current will not be reduced by the resistance of the conductors. The test current is supplied by a constant current source, not a constant voltage source, so the current will be exactly what it should be.

 

[Deleted member 26818]

If the test current produced by the tester is then subject to resistance between the tester and the RCD, what current would be detected by the RCD?

 

[davesparks]

If the test current produced by the tester is then subject to resistance between the tester and the RCD, what current would be detected by the RCD?

Exactly the same current as the tester produces. Current does not diminish through a circuit.

 

[Deleted member 26818]

Exactly the same current as the tester produces. Current does not diminish through a circuit.

Lol.​Lol.

 

[davesparks]

Lol.​Lol.

What is that supposed to mean? Of you think I'm wrong please explain.
Current does not diminish at it travels through a conductor. If what you are suggesting was true then you wouldn't ever see any current in the neutral!

 

[Dave OCD]

After 7 pages of all this (and yes I know the approved way of testing an RCD), I still like to test the RCD at the circuit/s I've worked on [such as additional sockets for example].
It's just good to know that you're actually simulating a fault where it might actually happen and seeing the disconnection times at the business end of the circuit as it were, gives me additional peace of mind.

 

[davesparks]

After 7 pages of all this (and yes I know the approved way of testing an RCD), I still like to test the RCD at the circuit/s I've worked on [such as additional sockets for example].
It's just good to know that you're actually simulating a fault where it might actually happen and seeing the disconnection times at the business end of the circuit as it were, gives me additional peace of mind.

So you get better peace of mind carrying out the test in such a way that could give a false pass?

Any earth leakage on the outgoing circuits will bias the RCD to trip at a lower test current than if it was tested in isolation.
With a 10mA existing earth leakage the tester could apply 30mA test current to trip the RCD yet the RCD is seeing 40mA before it trips.

 

[Dave OCD]

No I do it at the RCD initially, for the sake of a few seconds I also do it at the end [unless it's a RFC] of the circuit/s in question - with all other final circuits switched off. So assuming the circuit in question has already undergone dead testing and produced good insulation resistance results how can there be earth leakage to confuse the tester ? If anything I'd expect to see slightly higher tripping times at the end of the circuit.

 

[davesparks]

No I do it at the RCD initially, for the sake of a few seconds I also do it at the end [unless it's a RFC] of the circuit/s in question - with all other final circuits switched off. So assuming the circuit in question has already undergone dead testing and produced good insulation resistance results how can there be earth leakage to confuse the tester ? If anything I'd expect to see slightly higher tripping times at the end of the circuit.

If the tripping times change due to the tester being at the end of the circuit then the RCD is faulty. If anything it may be quicker as RCDs tend to get a bit quicker after a few operations.
The tripping time will be exactly the same wherever you put the tester assuming that there is no earth leakage to interfere.
As far as the IR results go, what exactly are you calling 'good'? If there are a number of circuits then their combined insulation resistance may be quite a bit less than the individual circuits

 

[Dave OCD]

Tripping times are never exactly the same, if I'm getting >10 Megohms on older installations I'd say that was good, would expect to see >200 on new wiring though.

 

[davesparks]

Tripping times are never exactly the same, if I'm getting >10 Megohms on older installations I'd say that was good, would expect to see >200 on new wiring though.

Only 200? I'd expect a damn sight more than that on new installations.

 

[Dave OCD]

Yes of course more like >2000 but just based the reply on a commonly used figure- possibly older testers showed >200 as their upper limit ?