RCD tripping problems

[gavin.sibley]

Hello all,

I'm having a problem with a nuisance tripping RCD, ran an RCD test on a board and results showed that RCD was knackered, swapped this out for new and tester again failed to trip the RCD, however customer is telling me of nuisance tripping 6-7 times a day whenever they try to use an appliance.

Is there any fault in a system that could cause an RCD not too trip under test, but yet trip whenever an appliance is being used. I have done all other tests on circuit and all show reasonable results for age of installation.

Thanks,
Gavin

 

[AdieB]

Where are you testing from? CU or at socket outlet?

 

[AdieB]

Sorry just noticed you tested at board. Try testing at socket outlet, some memshield do not trip if tested at board may have a similar problem.

 

[gavin.sibley]

Tried from both socket and board with same results...

 

[markc123]

Firstly if your 'new' RCD has failed to trip on testing, you need to be replacing it again...that's obviouslly if you meant it failed to trip at 1x and 5x on both cycles.

Secondly, yes - faulty appliances can take RCD's out...i would advise on PAT testing the appliances that seem to be causing the nuisance tripping.

 

[gavin.sibley]

Yes that's exactly what I meant, problem is, it trips with every appliance in the house and the shower, that's why I was wondering whether there was any sort of wiring fault that could cause this problem?

 

[Tuttle]

Could it be a neutral fault?

 

[telectrix]

that's what i'm thinking. retest RCD with both load L and N dissed. if it trips then, it's a wiring fault, poss. a N-E fault that inhibits your tests but causes tripping when under load.

 

[Octopus]

What is the Ze of the install?

 

[gavin.sibley]

Ze from what I can remember (haven't been there for a few days as customer has been away) is around 0.15ish. There is a circuit in the install which is showing a dead short between all three conductors, although this is obviously switched off in the board, could this fault possibly be the cause of the RCD failing to trip?

 

[Tuttle]

Ze from what I can remember (haven't been there for a few days as customer has been away) is around 0.15ish. There is a circuit in the install which is showing a dead short between all three conductors, although this is obviously switched off in the board, could this fault possibly be the cause of the RCD failing to trip?

I would try disconnecting the neutral of this circuit

 

[bertt]

Hi,
If you use an 30mA/RCD 1P + N The protection for group circuit will function as a cumulative effect of these circuits is true.
-Check if RCD is fail-safe or not (only 30mA or 30mA OR AND 63A as specifications on module(please take a picture for me of CU).
-Check the CU open box for any trace (visual verification connection) of MCBs overheating as part of the group. (Flashlight head, screwdriver ..)
-You could take the measure of voltages before and after MCBs with high loads running. Different values ​​are indications of failure or penetrations of the insulation. For this verification task.
Other not yet IR tests.
Thank you.

bertt.:sorcerer:

 

[Silly Sausage]

Ze from what I can remember (haven't been there for a few days as customer has been away) is around 0.15ish. There is a circuit in the install which is showing a dead short between all three conductors, although this is obviously switched off in the board, could this fault possibly be the cause of the RCD failing to trip?

If the N and E are still connected at the board, the RCD will trip as soon as any load is applied.
Disconnect that circuit completely.

 

[Octopus]

Ze from what I can remember (haven't been there for a few days as customer has been away) is around 0.15ish. There is a circuit in the install which is showing a dead short between all three conductors, although this is obviously switched off in the board, could this fault possibly be the cause of the RCD failing to trip?

Hum, maybe a clue here. Did you have everything unplugged/isolated?

EDIT: When did the tripping start, on what circuit, who's been meddling?

 

[guest119]

Ahhhh the weekly rcd tripping thread, late this week though.
This will no doubt follow the route of all the others where the blind lead the blind and the senior knowledgeable sparks are ignored when shouting IR test.

 

[Darkwood]

Just seen this thread ...... yes no doubt we have a poor insulation resistance and wont effect the rcd until circuit is loaded had this myself with any load plugged in trips rcd and the fault was found on a lighting feed that had been trapped ..... best way to quickly find it is if you are lucky enough to obe able to repeat the tripping yourself by using the shower or plugging in a load then do this and one by one disconnect all the other circuits in the board repeating the load test.... if it still trips with all other circuit fully disconnected then the issue is your circuit your loading.

To note! This problem can also be brought on by a circuit not on the rcd or even on another rcd or rcbo. It sounds counter-intuitive but took me 3hrs first time i came across this but only 10mins now to source offending circuit if of course you have the same problem, the last time i resolved this issue the customer had used 3 other Electrical companies who all failed to isolate the problem but experience is key here as i went in and left within half hour and fault resolved.

 

[markythesparky]

Yes that's exactly what I meant, problem is, it trips with every appliance in the house and the shower, that's why I was wondering whether there was any sort of wiring fault that could cause this problem?

Is it wired backwards. I remember a sparks wired a Crabtree on the wrong way round once and it stayed on until any appliance was turned on.