MEM Memera 2000 RCD Trips out

[RogerJohn]

Since the beginning of the month ( so nearly four weeks now ) my RCD has been constantly tripping out. I've had an electrician check out the system - he couldn't find any fault with either the board or the sockets - having spent half a day testing everything. We had EDF Emergy test their supply - nothing (although the board did trip out while he was here maybe four times leaving him shaking his head)!
We've isolated eveything. The usual suspects - boiler - fridge/freezer - you name it. I Even went around the house this morning clearing out the cobwebs from inside the light sockets - 7pm tonight, guess what....
There is absolutely no pattern to when it will trip. If I switch off one of the circuits and it trips when I turn it on, the next twenty times I repeat the action it won't!!! It'll even trip maybe three or more times when we're in bed, but then it'll go a day or two when it won't do that either. I am at a complete loss as to know what to do. Please Help Help Help.

 

[baldelectrician]

have had this before with a mem 2000 rcd. turned out to be a supply fault.

do your lights flicker more than they used to?
is your supply overhead?

the voltage dropped and the rcd tripped.

 

[ricicle]

Did the electrician test the RCD itself?
Have you any evidence of vermin?
Any chance there could be some water leakage onto a socket/switch/joint-box anywhere?

 

[RogerJohn]

Thanks for the prompt replies.

No flickering of lights ( in fact that was one of the first things the guy from EDF asked when he checked the supply up to the meter). The supply is underground - in from the street.

There is no visual evidence of mice etc and I've been around the house and can't see any water or even damp patches anywhere. My wife was here when the electrician came and she thinks he did check the RCD, but I'm not sure coz I wasn't here. What he said was that the power was strong and constant - whatever that means!

 

[ColJack]

these things are invariably hard to find the cause of..

by "isolated" do you mean just turned the breaker off or actually removed the wiring ( live neutral and earth ) from the CU terminals?

many people who claim to have "isolated" a circuit just turn the breaker off then scratch their heads when a neutral earth fault still trips the RCD..

the best cure for these things is John's favourite thing inthe world.. RCBO's..

remove the RCD and fit RCBO's to just the circuits that need them..

if one trips then it's that circuit and you've at least narrowed it down..


there is certainly a market for "RCB BUSTERS..." where a datalogger could be hooked up and left for a few days to do it's thing.. recording voltage spikes and drops, leakage curents and triping events..

i saw something on merlin gerin's website about a "pulse logger".. not sure if that's the sort of thing..

 

[RogerJohn]

Phew! Am just a punter so don't understand what you suggest. By isolating all I've done is ,Item by Item, remove the plug fom the socket of each appliance until the RCD blows and it did evey time. And I've done that to everything in the house.
I will get another electrician in to check this over - I'm light years beyond my basic skills, but any direction that I can point him towards to solve this problem without having to re-mortgage would be appreciated!

 

[fireman22]

roger, i had a simular problem at my mates house. rcd tripped randomly no pattern etc. it was a different make to yours however. i tested his rcd with and without wiring i couldnt make it trip etc. my tester showed no fault with his rcd. this went on me going back and forth. then i bought a new rcd fitted it in and problem has gone. so maybe worth just changing rcd at least you will have a starting point and can then rule out the rcd. if your electrician has an understanding with his wholesaler they might even allow him to take it to do a test for you without a charge.

 

[RogerJohn]

Thanks Fireman22 for the reply.
If I'm honest, I feel it might be the board as well, so I'll take the advice and get an electrician to try out a replacement RCD unit - will keep you posted.
Again, thanks too all.

 

[Lectrician]

these things are invariably hard to find the cause of..

by "isolated" do you mean just turned the breaker off or actually removed the wiring ( live neutral and earth ) from the CU terminals?

many people who claim to have "isolated" a circuit just turn the breaker off then scratch their heads when a neutral earth fault still trips the RCD..

the best cure for these things is John's favourite thing inthe world.. RCBO's..

remove the RCD and fit RCBO's to just the circuits that need them..

if one trips then it's that circuit and you've at least narrowed it down..


there is certainly a market for "RCB BUSTERS..." where a datalogger could be hooked up and left for a few days to do it's thing.. recording voltage spikes and drops, leakage curents and triping events..

i saw something on merlin gerin's website about a "pulse logger".. not sure if that's the sort of thing..

There is no cure for this - and fitting RCBO's is certainly not a cure

A sparky who can work an insulation tester, and know how to correctly use it to find these types of fault is what the OP needs.

 

[ColJack]

so my phrasing was bad..

i meant "the best way to FIND and cure these things...."

rcbo's help by not tripping every circuit on the board after the RCD.. so it norrows the search down significantly..

also most RCBO's that I've seen have the neutral connected through it and break the neutral also.. making "isolation" easier..

as for using a insulation meter to find the fault..

that's not always going to be possible..

the rcd might be tripping due to voltage drop when a neighbour cranks up his welder..
it might be tripping when water gets inside of an outside light... if it's been dry for a few days when you go then the fault will have dried up.. no sign of it..
it might be a stray neutral strand on a dangly metal light fitting that swings a little every time someone opens a door..
it might be a cable run accross central heating pipes that has worn through the neutral but only touches the pipe when someone steps on that particular spot..

or any number of possible reasons..

any good sparks will do a test on the cables to see if it's an insulation breakdown or just a straight short.. but once that's been ruled out and it still trips then theres a problem...

 

[JohnD]

RCBOs are great!

Although you can get MEM DP RCBOs, the common ones are only SP, and they fit into the same space as the MCB.

But they are a handy way to identify a particular circuit with a fault on it, and avoid the inconvenience of losing several circuits due to a fault on one.

They can also get round the problem of slight earth leakages from multiple circuits accumulating to enough to trip the RCD.

How many circuits are in your CU; what are they; which are the ones that go through the RCD? Do you have any spare ways in the CU? Which side are they?

If the boiler goes through the RCD, have you tried turning off the DP switch or FCU that supplies it? This is the time of year for heating to be turned on, and water in the boiler r pump often causes an electrical earth leakage.

Also try turning off the immersion heater and cooker at their DP switch. Pretty well all other appliances have a plug you can pull out.

 

[securespark]

Don't forget:

Floodlights, outside electrics...

 

[RogerJohn]

Thanks again for the suggestions.
I opened up and checked every light switch, pendant and ceiling fitting in the house and did any tidying necessary - though other than some exposed cable(now snipped and re connected) there were no apparent faults.
I've switched (and unplugged) every appliance including the central heating and fridge freezer etc - it still blows. At one point I disconnected every appliance in the house (Apart from the lights) - It still blew. Tonight it's blown 6 or seven times already and it's only 7 18pm.
I'm hoping the sparks due to come this week may have some success - will definitely pass on the advice offered - see how it goes from there.
Thanks

 

[JohnD]

"How many circuits are in your CU; what are they; which are the ones that go through the RCD? Do you have any spare ways in the CU? Which side are they? "

you are talking as if even the lights go through the RCD - this is undesirable. you only need the sockets and electric shower (if any) to go through it.

IF it is a Live/earth fault (but not if it a a Neutral/Earth fault) you will probably be able to isolate it by turning off the MCBs for most of your circuits; then, if it still happens, turn off the remaining ones and turn on jsu one (usually the lights) of the others.

If it still trips with all MCBs off, it is prorobably a Neutral/earth fault.

Can you think of any nails or screws into walls or floor that might have penetrated a cable?

Do you suppose you have rodents gnawing the cables, especially under the floor?

 

[securespark]

At one point I disconnected every appliance in the house

Now try disconnecting from the CU - each circuit in turn that is on the RCD.