How to deal with RCD tripping - external noise

[daba]

Good thinking riggy, NE on something that barely draws current, and it would be irrelevant if he even had a rod or not, would be interesting to find out if Ze was done disconnected.

I believe Ze was measured with all the protected circuits isolated (CB's off), nothing was unplugged in the house. All I have on the non-protected end of the board is the house alarm, and a fridge/freezer, which was replaced for another reason after the problems started. The report shows N-E at 0.35 M ohms for all circuits.

Don't forget Ze has been measured twice now, once by the DNO (0.14 ohms), and once by Haste (0.24 ohms). I think we just have to accept that it is that low.

 

[ParkySparky]

N - E at 0.35 that could well be your problem then! A neutral to earth fault will trip rcd no problem!!!

Every circuit at 0.35 N - E??

 

[OnOff]

The global IR reading isn't really going to identify the circuit that may be causing the problem. Better to isolate and test each one individually surely?

 

[daba]

N - E at 0.35 that could well be your problem then! A neutral to earth fault will trip rcd no problem!!!Every circuit at 0.35 N - E??

Have just spoken with Haste technical about the apparent low N-E reading, and he confirmed that it is a typical figure obtained when testing with CB's closed, i.e. all the devices in the house connected, and is due to all manner of things, including, he said, the main culprits being surge suppression devices built into equipment. He confirmed that the "Limited Electrical Condition Report" is satisfactory in every detail, and I have nothing to worry about.

 

[ParkySparky]

Something's not right! Where did he do insulation resistance test from? Your telling me he's left everything plugged in and insulation resistance tested all the final circuits???????????????????????????????

 

[daba]

Something's not right! Where did he do insulation resistance test from? Your telling me he's left everything plugged in and insulation resistance tested all the final circuits???????????????????????????????

He said it was a test they devised themselves - I'm not going to argue with them.

 

[ParkySparky]

Never heard of anything like it!

Anyone else?

 

[Riggy]

To quote one our illustrious members (KME I think?) "If you haven't found the fault, you haven't done enough testing"

You haven't found the fault, but if you look in the last six or seven post (including your own) I think you're getting warm!

 

[steptoe]

Have just spoken with Haste technical about the apparent low N-E reading, and he confirmed that it is a typical figure obtained when testing with CB's closed, i.e. all the devices in the house connected, and is due to all manner of things, including, he said, the main culprits being surge suppression devices built into equipment. He confirmed that the "Limited Electrical Condition Report" is satisfactory in every detail, and I have nothing to worry about.

its not apparent, it IS low,

its NOT satisfactory, there is either a fault somewhere, or their woefully flawed method of measurement is not a proper test at all,

who exactly agreed to the limitations, and what are they?

He said it was a test they devised themselves - I'm not going to argue with them.

well, its certainly NOT a test recognised by BS7671

Never heard of anything like it! Anyone else?

me neither, its a flawed situation.

Riggy, as you so rightly quoted mr KME, if you havent found the fault you havent done enough testing,

except, it looks as though they may have found the fault and simply decided to ignore it,

0.35 , and there was me thinking anything under 0.5 wouldnt be acceptable........ :|

 

[Steve3948]

Well in the old days 0.5 was acceptable in conduits and trunking anyway.

0.35 will not force the trip out IMHO, not even on a nuisance level unless other leakage is adding to it at some point.

 

[ParkySparky]

Also how did they IR test it with mcb's closed? Surly they would be at least open so no voltage on final circuits?

I still don't know how your tv etc is still working with at least 500v put down it?

I would not trust any test you've had done so far by the sounds of it!

iMHO you need to basically stop being tight and pay for a proper spark to do a proper test, who will give you a proper cert!!!

Before you start blaming some random pub lights for faults which sound to me as though they are clearly in your installation!

 

[davetheglitz]

ohms law - 30mA leakage at 230v - R=V/I 230/0.03 = 7666ohms to cause a trip = 0.00766M.

0.35M may be an indication that something on the system may be breaking down - or an indication that a surge protected extension lead has been left in - but it won't cause tripping.

 

[ParkySparky]

Dave how did they get this reading testing the way has been described though?

 

[Steve3948]

Dave how did they get this reading testing the way has been described though?

Global test, posted above, N-E

 

[the professionals]

it is definitely a dno problem , had this before when a grass cutter would knock r c d out on a property 100 meters away, you need to badger them or get am ex dn o guy out which happened in my case was poor connections on d n o side which i could nt touch.

 

[davetheglitz]

[Dave how did they get this reading testing the way has been described though?

/QUOTE]

I don't know for certain what these guys did, but as a global quick and dirty diagnostic test on single RCD systems I switch on lights - if filament lights are fitted anywhere this will prevent a voltage build up between L and N. I switch off at the main switch/RCD then test insulation at any available socket from L or N to E at 250v (prevents surge devices from kicking in).

Anything less than 0.25M sets alarm bells in my head - then start investigating individual circuits.

Just a thought - PAT test passes as 2M. Six items like this plugged in gives 0.33M insulation to earth.

---------- Post Auto-Merged at 20:34 ---------- Previous post was made at 20:12 ----------

Thought this might help

http://www.talk.electricianforum.co.uk/question-answer-board/890-upstream-residual-current-device-bs-en-61008-tripping-2.html

 

[daba]

[Dave how did they get this reading testing the way has been described though?

/QUOTE]

I don't know for certain what these guys did, but as a global quick and dirty diagnostic test on single RCD systems I switch on lights - if filament lights are fitted anywhere this will prevent a voltage build up between L and N. I switch off at the main switch/RCD then test insulation at any available socket from L or N to E at 250v (prevents surge devices from kicking in).

Anything less than 0.25M sets alarm bells in my head - then start investigating individual circuits.

Just a thought - PAT test passes as 2M. Six items like this plugged in gives 0.33M insulation to earth.

---------- Post Auto-Merged at 20:34 ---------- Previous post was made at 20:12 ----------

Thought this might help

http://www.talk.electricianforum.co.uk/question-answer-board/890-upstream-residual-current-device-bs-en-61008-tripping-2.html

OK guys - I'm backing out of the discussion about N-E impedance testing : Haste did it the way they did it, and I'm quite sure they know what they are talking about, like I said I'm not arguing, especially as they say I've passed with flying colours.

It seems as though you all have your own ideas, and you all test things in different ways, and I appreciate there's more than one way to skin a cat (or was it rabbit?).

But it doesn't help my situation you all barging in and pointing fingers - what I need now are ideas on how this could be happening that I can bounce on the DNO, because I am beginning to think they have no idea how to be a DNO, or don't know what DN they are O for, if you get my meaning.

We have determined that another consumer is affecting my installation, and I have correlating data to prove this.

I have changed a perfectly good trip (according to the manufacturer and BS).

Haste have "passed" my installation. The DNO asked for the tests to be done, and they are paying for them, so I can't ask them to come and do "proper" tests, so if the DNO won't accept their findings, then they must ask them to revisit and do tests that they will accept.

So the cause of the trips is external - i.e. there is a disturbance (an impulse) that is finding its way into my protective RCD device and causing a L-N imbalance of > 15mA

The DNO must now take responsibility for this and FIX IT !

We are now 5 months since the problem started - where will it end..?

---------- Post Auto-Merged at 00:40 ---------- Previous post was made at 00:25 ----------

its not apparent, it IS low,its NOT satisfactory, there is either a fault somewhere, or their woefully flawed method of measurement is not a proper test at all,

who exactly agreed to the limitations, and what are they?

well, its certainly NOT a test recognised by BS7671

me neither, its a flawed situation.

Riggy, as you so rightly quoted mr KME, if you havent found the fault you havent done enough testing,

except, it looks as though they may have found the fault and simply decided to ignore it,

0.35 , and there was me thinking anything under 0.5 wouldnt be acceptable........ :|

The DNO organised the test, the DNO payed for the test, and if the test wasn't to BS, then that is not my problem. I hear you all, if Haste are conducting tests that are not BS approved, then how can they have any credibility? My guess is they do the "quick, cheap, unapproved" test, then investigate further if the reading is lower than typical - and it's just a guess, so don't quote me.....

However, if the DNO accepts the test results, and actually does something to fix the problem, then i'll be happy.

 

[steptoe]

The DNO do NOT work to BS7671 so that is irrelevant to them.

Haste have NOT done a proper or recognised test,

I dont know what else you want to hear.

 

[daba]

N - E at 0.35 that could well be your problem then! A neutral to earth fault will trip rcd no problem!!!Every circuit at 0.35 N - E??

That doesn't surprise me at all, considering the neutrals are all connected to a single fat bus-bar in the CU, and there is no switching on the neutrals - I would expect that N-E was consistent across the board.

---------- Post Auto-Merged at 00:53 ---------- Previous post was made at 00:51 ----------

The DNO do NOT work to BS7671 so that is irrelevant to them.Haste have NOT done a proper or recognised test,

I dont know what else you want to hear.

I want to hear some ideas how the DNO could have done streetworks in such a way that an impulse from another user on the grid is tripping my RCD - simple.

---------- Post Auto-Merged at 00:54 ---------- Previous post was made at 00:53 ----------

The DNO do NOT work to BS7671 so that is irrelevant to them.Haste have NOT done a proper or recognised test,

I dont know what else you want to hear.

What BS do the DNO have to work to ?

 

[steptoe]

None AFAIAA ESQCR is their reg.

First thing you need to do is a proper OR test before you can go accusing other people of anything. Only my opinion mind,

But that test result for your property proves nothing, you could have a DNO fault, or you could have an internal fault, that test has NOT ruled you install out, that is what makes it worthless,

Do you really want to get this sorted, or just to blame someone?

Get an independent test done and bill the DNO for it if it probes your install to be A-Ok .

---------- Post Auto-Merged at 01:02 ---------- Previous post was made at 01:02 ----------

Ootherwise you will.end up in circles