Slow rcbo times ??

[burntwire]

No but no load and nothing plugged in, Why would this be an issue ?

 

[Spark123]

Any capacitance in the cables, RFI filters etc etc can have an effect on the reading. Odd that it should trip when you plug your tester in as opposed to direcly connect it to the RCBO as the test should cause a 30mA leak regardless of where it is connected in the circuit.

I'd try them in isolation, possibly even take another RCD tester with me to try.

 

[burntwire]

OK Thanks , because none of them tripped out this way I assumed it may have been normal for an RCBO to behave like this,

 

[Spark123]

Nope, if they don't trip then as an RCD that is a fail
As there is more than one though makes me suspicious that the L probe was onthe wrong terminal or the instrument is playing up.

 

[JohnD]

I have MEM pods at home and they all trip in good time. I do not have the results to hand though but yours sound strangely slow. I think you may be able to find "typical" trip times on the MEM website.

 

[RF Lighting]

Dodgy set of 'flying leads' on your test kit, but your plug in lead is ok?

 

[ricicle]

I have experienced this before and it turns out the Neutral probe was not touching the terminal properly on the outgoing side of the RCBO. The tester did not pick this up as it must have stayed energised via the earth connection.

 

[burntwire]

Thanks for your replies, my tester is due for calibration next month so i may snd it off early !! thanks again

 

[Spark123]

What make/model of tester is it?

 

[hairyben]

I have experienced this before and it turns out the Neutral probe was not touching the terminal properly on the outgoing side of the RCBO. The tester did not pick this up as it must have stayed energised via the earth connection.

Thats exactly what I was pondering, does the OP have correct voltage readings across all 3 conductors on his tester? Probe tip shrouds removed?

RCBO's can be a b---- for this, many won't accept insulated screwdrivers either.

 

[burntwire]

Its a Metrel 61557, I did have a voltage reading so im still confused !! going back on Wednesday so will try again !

 

[Spark123]

Don't know about Metrels, maybe RF can comment? The Megger MFT 1552 I have will do RCD tests with only the L and E leads connected.

 

[ricicle]

The problem I encountered above was with the Metrel Easitest.

 

[RF Lighting]

Give me an hour, and I'll go try it with mine.

 

[RF Lighting]

Now this is curious.

I have just carried out an official scientific DIYnot experiment.

32A 30mA Merlin Gerin RCBO supplying one of my garage ring finals.
Using my calibrated metrel instaltest 61557

Here are the tests I tried.

1. L&N connected straight to RCBO. E not connected. Display shows "PE" and will not test.

2. L connected straight to RCBO. E connected to earth. N not connected. Display shows "PE" and will not test.

Thus I conclude it was not a missed connection to neutral.

3. L&N connected straight to RCBO. E connected to earth. Circuit still connected to RCBO. 1/2xI<delta>n = ok. 1xI<delta>n = >300mS (No trip so it will not try 5xI<delta>n)

4. L&N connected straight to RCBO. E connected to earth. RCBO tested in isolation. All tests OK.

5. L,N,E connected to a socket outlet using plugtop lead, with same load on ring as in test 3. All tests ok.

How odd.

It will not trip when a load is connected, and the tester is applied direct to the RCBO terminals, yet it will when using the plug in lead.

I didn't take any IR readings for the circuit, but they are not really relevant for this experiment.

For some reason the forum software does not support the <delta> symbol