RCD ramp testing.

[EddieCurrent]

Hello All,

I would like some help with an RCD 'tripping' problem please.
No apparent pattern to when it trips, but has been tripping since new split load c/u was fitted @3-4yrs ago.
(Home has 4-5 fridge/freezers and quite a lot of pc equip ! I am thinking earth leakage).

The RCD tripping 'times' are all ok, and seem quite normal. However, the meter I used has a ramp test function, and I found the 30mA RCD was tripping at 15-18mA.
I thought this to be a bit low, so I replaced the RCD and now I am getting a reading of @21mA.

What sort of figure would you expect to get from the tests ??? I thought @27mA

(I still think its a dodgy fidge/freezer )

Thanks in advance for any help or abuse
Ed.
123 too.

 

[dingbat]

21mA is entirely normal for a 30mA RCD.

 

[JohnD]

Are you testing at the RCD with all circuits disconnected, or at a socket? There is bound to be a bit of background leakage and any transient currents will add to this and possibly give nuisance tripping.

Is the cooker or the Immersion heater on the RCD?

Of course, if you had RCBOs.....

 

[securespark]

How are you testing the RCD?

Yes, if you get as low as half the trip level, it could cause problems with nuisance tripping.

I like to see a minimum of 18mA really. As long as it's not as low as 15mA, it should not nuisance trip (well, not due to the RCD anyhow).

But you must test the RCD isolation. Remove the neutral from the outgoing side of the RCD. Or remove the neutral from the busbar, or whatever. Then switch off all MCB's on the RCD.

Apply the test probes to the incoming earthing conductor, and the outgoing live & neutral terminals of the RCD, having isolated all outgoing circuits from it.

This way you will get an accurate reading.

As a technical advisor in my company, I discovered 99% of sparks were testing from a s/o which often gave the meter misleading readings and it would fail the test, sometimes tripping on 1/2 x test, sometimes the 5 x test would fail, even though there was nothing wrong with the RCD.

I rang the manufacturers of both RCD's & the test equipment and between us we came to the conclusion that the meter would read stuff in the circuit that would create a misleading reading & fail the test, even though the RCD was healthy.

 

[securespark]

You can go off a person very quickly, John....

 

[JohnD]

heee heee!

 

[securespark]

Looking for another emoticon [one wringing the other's neck]

 

[JohnD]

Well done John, I wish I was as quick as you

 

[securespark]

You must live closer to the DIYnot server.....

Well done John, I wish I was as quick as you

[grudging acknowledgement of the above...]

 

[EddieCurrent]

Thank you for all your help and advice,
it hopefully will be taken aboard.
The test was carried out without appliances dis connected, through a double socket on the first s/o on 1 leg of the ring.
I am outing my fluke 1653 due to my being defined incompetent, but still have a hobby here.
As I only have this meter, and he is a good mate, i can only advise him that he has a dodgy appliance, which is causing excessive earth leakage and that this may( e/l) be causing this ???


Is there a way. other than a process of illum that I could find the cause of this, he has been a good mate and i personally would like to help him out, as he has helped me out b4.
I am not, doing or will have not done a stroke since my failed NIC assesment, this is a m8 thing.



Bernard, Secure, RF, pensdown, adam,ricicle,JD, big,crafty,plug.mst,Ding, I do thank you for all your help and input throughout my 'quest' for knowledge, albeit for a hobby. you are clever guys and having worked as a mate for 20yrs I respect and admire your knowledge and understanding of the 16-17th.

 

[EddieCurrent]

maximum e/l tables ??
spark123 too, sorry if I missed your name to the 'pro's..

Is big spark still about ?

 

[JohnD]

(sounding a bit disheartened)

Steady on, old chap! Nil desperandum!

Most likely there is a backround leakage, very likely from the washing machine, outdoor light, dishwasher, immersion heater and other assorted things that are likely to be wet. Plus the oven.

Chances are if you unplug/disconnect as many as you can of those, you will find the ramp test goes higher before tripping, because it will not be adding to an existing 15mA or so of leakage.

It may be possible to find the culprit(s) and either replace them or move them to the non-RCD side.

You can try your meter on the RCD direct with no circuits connected as well, I bet it will not trip so early.

 

[EddieCurrent]

Cheers JD,

Maybe I should just practice what I squeak, so to speak, if you'll pardon the pun !!


EddieCurrent




Joined: 12 Dec 2006
Posts: 224
Location: United Kingdom
Posted: Thu Mar 01, 2007 2:37 pm Post Subject:

--------------------------------------------------------------------------------

Hello,

Are you sure you should be looking into this yourself ? I think it would be best for your neighbour to get a 'pro' in.
No offence, but you must be very careful, and if you are not confident, or do not have the correct tools (neon drivers should be snapped in half and thrown in the waste bin) you may end up getting yourself in all sorts of trouble, I understand that you are only trying to help a neighbour but how far are you going to go ? have you checked to see if its on an RCD ? How will you test it ?

 

[securespark]

I'll second that, Flash!

I try to show the guys what a difference it makes - let's ramp through a socket and then do the same test in isolation. It does make a difference: usually the difference between a pass & a fail.

If you're looking for leakage, you need a fairly rare bit of kit but it's a godsend. It's a mA- sensitive clamp meter that you clamp on the main earthing conductor & it will register the leakage. By flicking breakers on & off you get an idea what each circuit is dumping down the cpc's. When you've done that, then you can look at individual appliances.

You can hire a lot of test kit these days, but haven't seen these clamp meters yet. I had been given one to trial, but I've returned it since.


Try: http://www.electrorent-europe.com/

 

[JohnD]

?Flash?

BTW, if you have RCBOs, the background leakage is bound to be less, because you have fewer outlets adding their leakages together, just the one circuit on the RCD.