Random Tripping on new consumer unit

[RF Lighting]

I would first of all run some tests for trip times and the ramp tests to both RCDs, with the RCDs in isolation. (Having circuits connected can throw up some misleading results).

Have you got an instrument to test the RCD trip times & ramp test?

A ramp test will tell you what the RCD actually trips at. Do both these tests with the RCD disconnected from outgoing circuits, otherwise your results (esp. ramp test) may be inaccurate.

[emoticon=raspberry]

I do not have any instruments to test trip times and ramp test. However I can probably get access to them.

[emoticon=raspberry] x2

 

[securespark]

Drat & Double Drat. Muttley!


Edit: Where's John when you need him? He'd have a raspberry-blowing emoticon...

 

[RF Lighting]

 

[securespark]

The penultimate one looks suitable.

Hmm.....I like the sheep one...

 

[JohnD]

Drat & Double Drat. Muttley!


Edit: Where's John when you need him? He'd have a raspberry-blowing emoticon...

Nope

Hmm.....I like the sheep one...

 

[gw3xjc]

Thanks for your trouble both. Still learning My 100ma trip is definitely not an s type, thanks for the picture! I will try and borrow some equipment later on in the week. I have to go to London for a few days on business but will check it out on my return. The RCD has trip once in 24 hrs.

Will be in contact on my return, thanks again for your efforts

Regards
Roger

 

[Adam_151]

Is it the 30ma that trips? sometimes the amount of leakage to earth through filters in appliances and electronic equipment can tip the rcd over the edge, remember that they trip at about 22ma in reality and computers can dump getting on for 1ma each to earth, and I've measured some of the white goods an applicances in the kitchen at about 2ma

I had a problem a while back, where the RCD was swapped out for one with 80A contacts in, and it must have been more sensitive than the old one (perhaps they make them more sensitive these days, or maybe it was just random tolerances, or perhaps because it was brand new) but we kept getting trips for no apparent reason serveral times a day when something just nudged the electrical balence a little and tipped it over the edge! The solution was to buy an RCBO (MCB with built in RCD) and install this on the non-rcd side of the board and move the kitchen ring circuit to that, the 'background leackage ' was then spread over two RCD devices and the problem went away

 

[JohnD]

RCBOs are great!

Most of my background leakage is from the washine machine.

 

[Softus]

Most of my background leakage is from the washine machine.

I blame the washing machine for my background leakage too (which is always worse after spicy food).

 

[gw3xjc]

Well the rcd has not trip for 36 hours. I agree with you guys that some of the filters can cause a leakage, and believe me with all my electronic gear, 4 computers, ham radio gear there is more than the fair share of filters in this house.

However, as I have had no tripping for 36hrs, it also has not rain for that period of time. Now here's the question I obviously know that if the live leaks down to earth with all its 230volt it will cause a large imbalance and trip the rcd. I know that if you short the neutral down to earth the same thing will happen.

I obviously know that if an outside light had water in it and the live leaked down to earth the trip would blow. Now here comes the question I don't know the answer to--------- If the neutral was leaking down to earth via a damp patch at what point will the rcd trip out. The neutral does not have 230 volt and I would imagine in an ideal world it would be at exactly the same potential as the eath. Some enlighten me gents

I ask this question because my suspicion at the moment is that possibly the outside lights may be the problem. However the live wire has been switch off from them but the neutral will still be connected.

Thanks to everyone who replied

Regards Roger, just come back from a business trip to London, bloody m25

 

[gw3xjc]

BTW Adam, nice one on the two RCDs, i like that idea old boy
Roger

 

[Softus]

...cause a large imbalance and trip the rcd. I know that if you short the neutral down to earth the same thing will happen.
.
.
.
If the neutral was leaking down to earth via a damp patch at what point will the rcd trip out.

Eh? What's the difference between the thing you know and the thing you don't know?

 

[gw3xjc]

Ok Softus I will try an explain my question in a different way to you.
The clue for you was the LARGE imbalance due to a SHORT circuit rather than a LEAKAGE :

I am try to establish at what point an rcd would trip if there was dampness in an outside light fitting for example when it's the neutral leaking down to earth.

If the live was leaking down to earth via a couple of k I would expect the rcd to blow, right? It has 230 volts on with respect to earth. Now I know if I SHORT CIRCUIT neutral to earth the rcd will trip.

What I Don't know is if the neutral was LEAKING to earth via the same scenario as above, a couple of k would it still trip as the neutral only has a very small amount of voltage above the earth potential.
I don't have PME




Regards

Roger

 

[Softus]

Hello Roger

The reason you have the question is that you're confusing yourself with your own terminology. Things should become clearer to you if you consider the question "At what current will the RCD detect an imbalance and trip?".

In case that didn't help, I'll continue...

Ok Softus I will try an explain my question in a different way to you.
The clue for you was the LARGE imbalance due to a SHORT circuit rather than a LEAKAGE :

The reason that this wasn't a clue "for me" is because they are the same thing "to me", but I can see that they're not to you.

If the live was leaking down to earth via a couple of k I would expect the rcd to blow, right?

Assuming that by "k" you mean 1,000 Ohms, then, in your example, the current would, in simplistic form, be (230 Volts / 2000 Ohms ) = 115 milliAmps.

Based on the above calculation, a 30mA RCD (or even 100mA) would be expected to trip, if the current were sustained for long enough. I don't know how you arrived at that conclusion though. Did you guess?

It has 230 volts on with respect to earth. Now I know if I SHORT CIRCUIT neutral to earth the rcd will trip.

If by "SHORT" you mean a sufficiently low resistance for the RCD to trip, then I'd have to agree.

What I Don't know is if the neutral was LEAKING to earth via the same scenario as above, a couple of k would it still trip as the neutral only has a very small amount of voltage above the earth potential.

In your example, if there were no leakages from other circuits supplied by the same RCD, then it wouldn't trip. But it isn't because you've used the word "LEAKING", it's because the resistance, at 2K Ohms, is sufficiently high.

I don't have PME

Does that mean that it's not your time of the month?

 

[gw3xjc]

Softus, I like the joke PME, very good

I apologies for the terminolgy, they are terms used in my field of expertise, sorry about that.

And yes, I fully understand the calculations.

I used the 2k ( oh sorry 2 kilohms, nb 2000 ohms) as an example, it's a figure I picked out of thin air.

Thanks to you guys I have learned a lot about the system and still learning. I will introduce a resistance between neutral and earth and I will see at what point it will trip, any guesses on the resistance that will cause it, i will let you know.

Thanks for your help
Regards Roger.