RCD Trip switch too sensitive

[Cornish Maid]

Last night we could hear distant rumbling of thunder, and within a few minutes our trip switch started going every 5 minutes. The storm never got very close, we couldn't even see the lightening, and I'd understand it if it was right overhead. Its always like this - Hubby says someone only has to f@rt 20 miles away and our trip goes!

We do have power to outbuildings, which might make the system more sensitive, but all the wiring is new and we have tried isolated the outside circuit during storms and it makes no difference.

Its a pain having to re-set the trip every few minutes, or wake up in the night to find everything has gone out, when we haven't even had the lightening close by.

Are there varying sensitivities on the RCD trips? Have we got one thats too "touchy"? I appreciate it is there for a reason and you cannot be too careful where electricity is concerned, but seems overkill that it trips so easily.

Any advice please?

Thanks

 

[Lectrician]

Can you take a photo of the offending RCD, and any other consumer units and distribution kit at the origin? Also the meter and service head etc?

I think we need to see exactly what you have before we can advise...

 

[Taylortwocities]

When the new wiring was done, what was the results of the tests done on the RCD? This information will be on the installation certificate that was given to you by the electrician who did the work.

The problem may be with the RCD and an electrician with an RCD tester could run trip and ramp tests to check if the RCD is not operating within the prescribed limits.

Alternatively, there may be a wiring problem, or a problem with some thing (or things) that are connected.

 

[ericmark]

The trips do come with variable sensitivity and time delays but to protect people it has to be 30mA @ 40ms so that option is not open to you.

However not all 30mA @ 40ms are the same. Some makes are better than others at resisting spikes. The speck says it must not trip at 15mA and must trip at 30mA. Some have indicators to show how close to the limit and don't trip until 90% rather than 50% there are also some that auto reset but at £300+ expensive.

The other method is less on each RCD the MCB's are changed for RCBO's which is a RCD and MCB combined.

 

[bernardgreen]

My bet is that an old voltage operated ELCB on a TT supply was not removed when the re-wiring occured and a PME was installed.

Maybe there are 30mA current operated RCDs fitted in the CU but the old ELCB could have been left in circuit as a handy isolator when the CU was changed.

If one side of the ELCB coil is still connected to the earth rod and the other side still connected the CPC then any discrepancy between true ground and the local incoming neutral that exceeds the ELCB's trip voltage will trip the "handy isolator". ( the CPC afte PME conversion will be connected to the incoming neutral )

The photos will give the answer.

 

[ban-all-sheds]

My bet is that an old voltage operated ELCB on a TT supply was not removed when the re-wiring occured and a PME was installed.

And they were well known for tripping during thunderstorms, particularly if the supply was overhead.

 

[Cornish Maid]

Thanks for replies. Sorry, when I said the outside/shed wiring was "new" I meant it was all done at the same time as the whole house rewired about 15 years ago. Prior to that the outbuildings had been DIY wired by the previous "make do and mend" farmer, and every time it rained the old trip went!

We had a leccie out a few years ago to wire up a couple of external security lights for us, and he looked at the RCD setup and just said "Oh some are like that" but didn't offer any alternatives. I am sure other people don't suffer like this every time there is a flash of lightening somewhere in the county! Just pleased its fairly accessible to keep switching it back on again.

I will try to get a photo up later, but for the meantime, details from the trip unit are:

Crabtree 854293 RCCB 80A 30mA List No: 380/030

If that means anything to anyone.

We were not given an installation certificate when the full rewire was done .

 

[Taylortwocities]

I will try to get a photo up later, but for the meantime, details from the trip unit are:

Crabtree 854293 RCCB 80A 30mA List No: 380/030

If that means anything to anyone.

.

That's a Starbreaker 30mA Double Pole RCD.
I guess that is fitted into your consumer unit? Need a photo of that, also a picture of the incoming electrcity supply head (where the sullpiers fuse is housed).

 

[ericmark]

Not all RCD's are the same here is a write up about Eaton Moeller RCD which monitor as well as trip so you have a warning when on the edge of tripping.

They state:- Thunderstorms or other temporary disturbances won't unsettle the digital RCD thanks to an optimised tripping threshold and a type "G" short-time delay which is independent from the supply voltage. In addition, load situations - however close to their designed threshold - will not require additional thermal protection, thanks to the integrated overload protection mechanisms. And regardless of the supply voltage, it will always perform its duty in compliance with the IEC/EN 61008 standard. By taking advantage of the LEDs that indicate the tripping threshold is being approached - but not exceeded - you can undertake corrective maintenance to the system before the situation develops further and thereby avoid an inconvenient interruption to your power supply.

Not a clue on price though. These

Untitled

• ericmark
• 6 Dec 2008
• 34

are very expensive around £350 I was considering using one for a disabled person who could not get under the stairs where the consumer unit was housed.

The problem in both cases is it also means a consumer unit change to take the RCD. So the other option may be RCBO's. But since you talk about a farmer you may well have a TT supply. With a TT supply really you should use double pole units.

I have had a RCD tripping which my RCD meter said was A1. Yet changing it for another one same make and design has cured the problem.

 

[ebee]

One cause of easy tripping can be on a PME system and a break in the CNE (PEN) Conductor .
When I say a break I don't mean a clean break but a fracture that opens up momentarily .
Loose connections on the incoming supply also might be a cause.
I'd still look for an ELCB though

 

[Taylortwocities]

I'd still look for an ELCB though

Why? The item that is tripping is not a voltage ELCB. Its a regular 30mA BSEN 61008-1 RCD. Its one of these THESE

 

[ebee]

ThankYou TTC , I stand corrected on that one.

 

[ebee]

I'd get the RCD tested although I think it rare to find one over-sensitive.
In my experience they either work correctly or fail unsafe (i.e. either not at all or outside the stated parameters). I'd also get the installation checked for leakage.

For example a 30mA RCD correctly tripping at say 16mA with an installation running normally at 14mA would only need an extra 2mA to cause a trip and thereby seem over-sensitive.

Note - I am not suggesting that 14mA is a normal amount of "leakage" for a healthy installation but rather that some installations can conspire to add up the total leakage to a highish figure and we'd not normally be aware of it.


I must say that the digital RCD with warming looks interesting, so thanks for that

 

[westie101]

although I think it rare to find one over-sensitive.

Indeed but as I related elsewhere I had to deal with a nuisance tripping RCD some years ago that would trip whilst the grass was being cut next door. All wiring and earthing checked and correct. Changed the RCD and the problem was solved.

 

[ericmark]

although I think it rare to find one over-sensitive.

Indeed but as I related elsewhere I had to deal with a nuisance tripping RCD some years ago that would trip whilst the grass was being cut next door. All wiring and earthing checked and correct. Changed the RCD and the problem was solved.

I have also had this. The RCD tests as being OK changed anyway and new one had same results with RCD tester, but did not trip all the time. I would always try just changing first before any expensive options were tried.