How to deal with RCD tripping - external noise

[Sharpend]

Haven' t read all the posts so forgive me if I'm only repeating something that has already been said.

Daba, it's simple, you get the tests that you keep saying that you'll get done, obtain all evidence to support your argument, you then write to the head office a strong letter outlining the problem that you are having and when it started. You state how disappointed you are with them not being prepared to eliminate their part in this. You then tell them that you will if necessary employ independant specialists to investigate and should the results of this investigative work determine that their part of the installation is at fault then you will be seeking further legal proceedings to recover costs and compensation for the duress you have endured.

Address the letter to the MD, then sit back and wait. It's surprising the response you can get once you get above the multiple layers of monkeys that regurgitate the company patter. You must insist on making contact with those above the monkeys otherwise your attempts will be futile.

Be prepared to carry out what you put in the letter, many times from my experience it is not necessary to have to, but you do t let them tho k that you won't.

 

[SPECIAL LOCATION]

Have you organised getting your house wiring tested yet?

Have you had your RCD tested yet? (Inc Ramp test)

Is it over sensitive? or all within spec?

well neither am i unsure about that - perhaps our more enlightened members can explain how turning off some substantial load 150m down the line can cause an L-N imbalance strong, and long enough to cause my RCD to trip, because without a shadow of doubt, that is what is happening !

RCD's do not need STRONG or LONG imbalances to trip...

That is the whole point!..

they are designed to trip within a very short time on a very small leakage current to stop people getting an electric shock....

i.e an imbalance of 30ma, or 0.03 of an amp

less than half a second duration..

Typically (depending upon type) within 200ms 300ms or 500ms with time delayed RCD's

Many modern appliances have a certain amount of natural leakage e.g. some desktop PC's & their monitors...

Many manufactures recommend that some cookers are not connected via an RCD...

If you had do have some electrically leaky appliances and a poor quality earth before.. (higher resistance)

less imbalance current would flow...

If you now have a better quality earth... your natural leakage current could have increased ..

{Lower resistance = Higher current!}

If your RCD is a bit oversensitive.. with a poor earth it may have been less susceptible to tripping ....

You have clearly convinced yourself that your installation & RCD are fine ..

But so far you still have not proved it to be within the tolerances of BS7671!

Step back...

Test your installtion..

Then come back with some facts..

I would probably try swapping the RCD, or temporarily fitting some other RCDs and splitting the installation to see if other RCD's trip!

But either way you are NOT looking for something Strong or Long causing your problem..

It is Small and Short!

:C

 

[steptoe]

Bang a rod in and go TT for a week or two, if that cures it then the fault is probably yours.

 

[daba]

Not been back for a while - guess I thought I was getting a hard time from some.

The DNO did their own tests on my house - no problems. They {sort of} ramp tested the RCD, it was a bit primitive being that they could only switch to 10, 15, 20, 25, etc mA, but my RCD didn't trip at 15, but did at 20. I don't think the instrument they used could tell the response time.

They said it was too sensitive. Legrand told me no : a 30mA trip should NOT trip at 15, but anything above it meets with the relevant BS spec., and i've read that spec as well.

But I had the trip changed anyway - paid for by the DNO, and at the same time another "wiring check" done by H.A.S.T.E. (The DNO organised this). I have their check sheet in my possession and the engineer said everything was good.

The new RCD is a different part number than the one it replaced - I'm told the old device has been superseded, but it is supposedly to the same spec.

I guess if I don't have any more nuisance trips I could say that the original trip was "over-sensitive" even though it meets the BS spec., but I have more than enough evidence that another consumer fed from the same sub-station caused me this grief, and the DNO should be investigating why the impulse is being put onto their supply grid in the first place.

The DNO is even saying they have no record of plans of a new supply cable being installed past my property, they told me this while I'm looking at the fresh tarmac strip in the pavement, and remembering the power outage while i was disconnected from the old and connected to the new.....

I did a flyer to all the neighbours who might be affected (I followed the fresh tarmac down the street, and I havn't had any replies.

The latest Ze on my installation was 0.24 : compared to the 0.14 I was told in a previous test. Even so it is well below typical....

So it's a waiting game to see if I get any more trips now the new RCD is in place.

---------- Post Auto-Merged at 01:10 ---------- Previous post was made at 01:07 ----------

Bang a rod in and go TT for a week or two, if that cures it then the fault is probably yours.

I'm already TT, have been for over 20 years, it appears as though being TT is to my detriment

 

[steptoe]

Not been back for a while - guess I thought I was getting a hard time from some.The DNO did their own tests on my house - no problems. They {sort of} ramp tested the RCD, it was a bit primitive being that they could only switch to 10, 15, 20, 25, etc mA, but my RCD didn't trip at 15, but did at 20. I don't think the instrument they used could tell the response time.

They said it was too sensitive. Legrand told me no : a 30mA trip should NOT trip at 15, but anything above it meets with the relevant BS spec., and i've read that spec as well.

But I had the trip changed anyway - paid for by the DNO, and at the same time another "wiring check" done by H.A.S.T.E. (The DNO organised this). I have their check sheet in my possession and the engineer said everything was good.

The new RCD is a different part number than the one it replaced - I'm told the old device has been superseded, but it is supposedly to the same spec.

I guess if I don't have any more nuisance trips I could say that the original trip was "over-sensitive" even though it meets the BS spec., but I have more than enough evidence that another consumer fed from the same sub-station caused me this grief, and the DNO should be investigating why the impulse is being put onto their supply grid in the first place.

The DNO is even saying they have no record of plans of a new supply cable being installed past my property, they told me this while I'm looking at the fresh tarmac strip in the pavement, and remembering the power outage while i was disconnected from the old and connected to the new.....

I did a flyer to all the neighbours who might be affected (I followed the fresh tarmac down the street, and I havn't had any replies.

The latest Ze on my installation was 0.24 : compared to the 0.14 I was told in a previous test. Even so it is well below typical....

So it's a waiting game to see if I get any more trips now the new RCD is in place.

---------- Post Auto-Merged at 01:10 ---------- Previous post was made at 01:07 ----------

I'm already TT, have been for over 20 years, it appears as though being TT is to my detriment

well,

I'll eat my hat

how certain are you that you are TT and you have a Ze of <1 ?

I'll eat my hat if that is the case,

that means you are right beside the substation.

someone somewhere, is either telling you porkies, or you are making assumptions.

---------- Post Auto-Merged at 01:30 ---------- Previous post was made at 01:28 ----------

BTW, they should be giving you an Ra measurement if you are TT , Ze is pretty much irrelevant.

 

[SLIPSHOD & SLAPDASH]

I'm already TT, have been for over 20 years, it appears as though being TT is to my detriment

headbang headbang headbang

 

[steptoe]

yet more mind reading we were expected to do

 

[OnOff]

Only just read this thread.........did we ever know/see what the "RCD" that's been replaced was? The fact that it was said to be "superseded" makes me wonder if it was an old voltage (rather than current) sensing (VOELB) jobbie.......

---------- Post Auto-Merged at 11:26 ---------- Previous post was made at 11:18 ----------

SORRY, my mistake. just re-read that it was a Legrand and seemingly f***ed so they replaced it......nothing a proper ramp test wouldn't have picked up on.....(got a head full of transient voltage thoughts at the moment!)

 

[daba]

well,I'll eat my hat

how certain are you that you are TT and you have a Ze of <1 ?

I'll eat my hat if that is the case,

that means you are right beside the substation.

someone somewhere, is either telling you porkies, or you are making assumptions.

---------- Post Auto-Merged at 01:30 ---------- Previous post was made at 01:28 ----------

BTW, they should be giving you an Ra measurement if you are TT , Ze is pretty much irrelevant.

I'm very certain I'm TT - there is no link to the main fuse from the earth bar in the consumer unit - an earth cable exits out the wall and down a steel conduit and is terminated to an earth rod. TT is ticked on the H.A.S.T.E. Electrical Condition Report, and Ze ohms is quoted as "237V @ 0.24". I'm not going to argue with a measurement done by Haste. FWIW the test equipment used was a Megger Model 1552, serial number quoted on the report, so almost certainly is calibrated and certified.

The substation is actually nearer to the pub than I am to it - I did a closer inspection of the ground-works they did, and it looks very much like the pub takes a different feed from the sub-station then the one I am on - which is even more confusing if the disturbance from the pub is going into the substation on one feed, and coming out again on another to trip my RCD. Perhaps the overlay installation team have left an underground connection in place between the two feeds - I don't know, and I don't think they know either - according to them they haven't installed a new supply cable past my house.... so why did they dig a trench and fill it back again?

I'm not understanding why you think my impedance to earth being low implies that I'm next to the substation?? My impedance is what it is by virtue of being TT isn't it? My path to earth doesn't relate to physical location of the substation.

I'm making no assumptions here, believe me.... I have just stated the facts to the best of my ability. Obviously I want this nuisance dealt with, and now that Electrical Condition tests have been done, can we at least agree that the problem is theirs, not mine ??

---------- Post Auto-Merged at 02:28 ---------- Previous post was made at 02:11 ----------

yet more mind reading we were expected to do

If you refer to me stating that I'm TT then I told you that in post #44

---------- Post Auto-Merged at 02:34 ---------- Previous post was made at 02:28 ----------

Only just read this thread.........did we ever know/see what the "RCD" that's been replaced was? The fact that it was said to be "superseded" makes me wonder if it was an old voltage (rather than current) sensing (VOELB) jobbie.......---------- Post Auto-Merged at 11:26 ---------- Previous post was made at 11:18 ----------

SORRY, my mistake. just re-read that it was a Legrand and seemingly f***ed so they replaced it......nothing a proper ramp test wouldn't have picked up on.....(got a head full of transient voltage thoughts at the moment!)

The DNO tested it : No trip at 15mA : Trip at 20mA : They didn't quote response times to me. My interpretation is that those figures met with the BS spec.

They made me obtain a new trip, and Haste (instructed by the DNO ) installed it last Sunday : The trip they took out was a Legrand 086 31 : the trip i got to replace it was a Legrand 089 12 - The supplier said it was "a part number change", but it could be a different design - I make no assumptions on that.

 

[Steve3948]

If you are on a Rod where is your neighbours either side of you ??

 

[pewter]

We had a customer with the same problem.

Few years ago when we had snow, the customer would wake up to a cold house as the boiler circuit had no power. The customer a rich city trader wanted it fixed , at any cost.

We moved boiler to unprotected side to keep him warm. We tested everything, moved things around.

DNO put a meter on to see what was happening. They said there side was ok.

We tested more and moved more around. Got DNO back to put meter on.

Eventually DNO admitted it was there problem, fixed it externally . Paid all the costs for us testing and mucking about .

It took months to get it all sorted out.

 

[daba]

If you are on a Rod where is your neighbours either side of you ??

I'm an end terrace...

 

[Steve3948]

I'm an end terrace...

So does your neighbour next door have a rod also, how far is it from yours.

 

[ParkySparky]

Daba do you know how the earth fault path works even on a TT system?

Why do you think the distance to the substation has nothing to do with your Ze or Ra if your TT?

 

[daba]

So does your neighbour next door have a rod also, how far is it from yours.

I can see the earth cable coming out of their house, but it disappears under the "lawn" travelling in the direction of my house. I lose site of it after about 3 feet. I can't see the top of an earth rod, but I can also see a second newer earth cable - it looks like they have a second rod added, and the cabling loops into one then the other. But as I said, the rod(s) themselves are buried. My rod is to the side of the house, a distance of approx. 35-40 feet.

---------- Post Auto-Merged at 11:26 ---------- Previous post was made at 11:21 ----------

Daba do you know how the earth fault path works even on a TT system?Why do you think the distance to the substation has nothing to do with your Ze or Ra if your TT?

All I know is there is residual current imbalance going through my board > 15mA which trips my RCD : I have no idea where that current is going to earth. As far as I am concerned, the RCD is doing the job it was designed to do, detecting an imbalance and protecting me and my kids from a possible electric shock.

 

[steptoe]

Im not convinced this is purely TT, Ive seen quite a few and never anything with a 'Ze' that low! That is truely an amazing reading for a 'TT' !

 

[daba]

Im not convinced this is purely TT, Ive seen quite a few and never anything with a 'Ze' that low! That is truely an amazing reading for a 'TT' !

Maybe it's because the ground is heavily laden with coal dust... These are miners terrace houses, the area was extensively mined up until the 50's as I understand it.

Somebody's got to be the lowest - do I get a prize ?

---------- Post Auto-Merged at 12:14 ---------- Previous post was made at 11:40 ----------

Im not convinced this is purely TT, Ive seen quite a few and never anything with a 'Ze' that low! That is truely an amazing reading for a 'TT' !

No sign of an earth via the incoming fuse and link...

See pic

 

[ParkySparky]

Im not convinced this is purely TT, Ive seen quite a few and never anything with a 'Ze' that low! That is truely an amazing reading for a 'TT' !

Maybe he waters the lawn alot

I just can't believe that the pub car park lights switching off is tripping your rcd!!!

 

[Riggy]

How about you've got a neutral to earth fault in your property?

Assuming Ze wasn't done properly, this would account for the unbeleivably low reading, and your RCD tripping if the pub lights somehow raise the neutral voltage for a fraction of a second.

 

[steptoe]

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.