Intermittent RCD fault

[esspeegee]

I attended a call out to look into the cause of intermittent tripping of an RCD which covered about 10 circuits. New property so everything under 12 years old. I took the cover off the board and tested the Wylex 30mA RCD trip times with my Fluke. All satisfactory. After this I pointed, using my WDE driver, to the RCD, while talking through the problem with the customer. Although my driver didnt touch the RCD, it tripped. I thought it was a co-incidence, but I repeated this several times and every time the blade of my driver got within 4mm of the RCD it tripped. If I used my finger or the driver handle, it didnt trip.

My driver isn't magnetic (as far as I can tell).

Im going to change the RCD before stripping out the many circuits but wondered if anyone had any feedback on this? The CU cover is metal and I wonder if it, like my driver is interfering with the RCD internals?

Thanks for any feeback

Simon

 

[SLIPSHOD & SLAPDASH]

No idea, but i am interested to know your results.

 

[NozSpark]

Maybe the ferrous tip and blade of your driver is interfeering with the electromagnetic field around the RCD?

 

[esspeegee]

I suppose it must be, but the board cover is metal, so wouldn't there be a risk of that interfering too? Its a snug fit after all. I have tried to get the same effect on a couple of other RCDs and they don't trip. The questions is, I suppose, does this sound like it might be a dodgy RCD and the cause of the tripping?

 

[steptoe]

its a weird one all right.

did you do any IRs, or a ramp test?

my first course would be to change the RCD too, then see what happens.

any chance its a dodgy copy?

 

[esspeegee]

I did do a tripping time test from a socket to make sure it wasnt tripping on 1/2 rated value and the RCD behaved perfectly. I didnt do any IRs or a ramp test because I was taken aback by the behavior of the RCD when my screwdriver came close to it after taking the board cover off. As the fault is intermittent I cant easily identify a suspect circuit. And as I said, the RCD behavior threw me. I'd say its not a dodgy copy and there have been no problems since the install 12 years ago.

 

[Nicky Tesla]

Have you tried putting a black cloth over the RCD so it cannot see you pointing?

 

[springcrocus]

It's got to based around interference to the magnetic field. Maybe you were charged up, as in static electricity? Just because your 'driver is insulated, it can still induce a voltage in something. Think about how capacitors/condensers work. Get your client to try the same trick, or wear different clothing and try again.

---------- Post Auto-Merged at 23:10 ---------- Previous post was made at 22:04 ----------

Thinking on a bit more, I reckon your RCD is sitting just below its tripping point with the standing earth leakage and your influence is tipping it over.

However, I don't think an RCD should be that sensitive to outside influence so it may well be faulty.

 

[esspeegee]

There might be an intermittent fault in one of the circuits. I haven't started to look yet because I was taken aback by the behaviour of the RCD. Judging by the feedback so far this seems an unusual incident.

I moved the blade of the driver around the RCD but it only ever tripped when 4mm away from the front face and below the test button. And let me stress I didnt need to make contact with it to cause the trip. And I repeated the problem a dozen times so its not like I've imagined it. The RCD didnt trip when I touched it or used the handle of the driver.

It must be the metal of the driver interfering with the magnetic field inside the thing and that is odd enough to warrant swapping the RCD. I'll re-evaluate my options then.

In the meantime thanks a bunch for the feedback. At least no one has called me a total idiot so I feel reassured I haevnt missed the bleedin obvious

Simon

 

[Steve3948]

Have you tested your driver to see it has not become magnetised ??

 

[esspeegee]

I just tried, and it has the tiniest bit of magnetism. Just enough to pick up tiny nails. That must be the cause, but I have tried several other RCDs and they haven't tripped. Do you think the original RCD is over sensitive or is this a typical response for some design RCDs? I'm feeling a bit foolish now...

 

[steptoe]

what I would like to try would be a ramp test of the RCD,

1 with NO loads connected, inc N&E disconnected too

2 with normal loads connected,

if you dont have an earth leakage meter this would show up fairly accurately how much leakage is on the present system, and just how close to tripping the RCD is presently.

it will also show just how sensitive the RCD is,

I had one last week that was tripping on x1/2 test, even though the ramp was showing 18mA, with loading on it was tripping at 4mA, so there must have been a leak of approx 14mA on the system already,

so very close to knockover point, turned out to be a dodgy fridge.

 

[Evans Electric]

There might be an intermittent fault in one of the circuits. I haven't started to look yet because I was taken aback by the behaviour of the RCD. Judging by the feedback so far this seems an unusual incident. I moved the blade of the driver around the RCD but it only ever tripped when 4mm away from the front face and below the test button. And let me stress I didnt need to make contact with it to cause the trip. And I repeated the problem a dozen times so its not like I've imagined it. The RCD didnt trip when I touched it or used the handle of the driver.

It must be the metal of the driver interfering with the magnetic field inside the thing and that is odd enough to warrant swapping the RCD. I'll re-evaluate my options then.

In the meantime thanks a bunch for the feedback. At least no one has called me a total idiot so I feel reassured I haevnt missed the bleedin obvious

Simon

Oh OK then ..... You're a total idiot !!!

---------- Post Auto-Merged at 18:20 ---------- Previous post was made at 17:41 ----------

Let us know your conclusions , I suspect a new RCD will solve the problem but its a strange one . Speak/ email to Wylex Technical !!! Probably cause another recall !!!

We had a tripping problem after fitting a new Crabtree Starbreaker which I've posted about before. We spent ages trying to find what was tripping RCD on a split- load , it tested out OK . We decided for some reason it was something within the heating electrics , left heating isolated, two days later it tripped again . Leaving elderly lady without half her electrics.

So I swear at the offending RCD and tap it lightly with a driver and it trips , so I flick it with finger and it trips !!!

The lady was there and she says "Oh it does that when the front door slams " :shakehead :shakehead:C

 

[esspeegee]

Update for anyone interested. I replaced the RCD like for like. (Wylex WRS 80/2) The new one didn't trip when my driver was close or even touching it. And the intermittent trip that led to the call out in the first place has not occured since.

Simon

 

[springcrocus]

Update for anyone interested. I replaced the RCD like for like. (Wylex WRS 80/2) The new one didn't trip when my driver was close or even touching it. And the intermittent trip that led to the call out in the first place has not occured since. Simon

It's nice to see someone close a thread with a result. Well done, that man. :Applaud

 

[steptoe]

right,

what we need now is this RCD sent on a round robin of members to see if we can replicate the fault,

whoi is up for it?

I personally want to see if it really is voodoo!