rcd circuits tripping out

hi, i have strange fault on my cu, it is in a house i just moved into too which was built in 2000. there is a split load cu with rcd on the one side containing the two ring main circuits. the fault occurs when i put the toaster on in the kitchen sockets , it trips out both circuits on the rcd. i have made some checks and it looks like there is a fault only on the one circuit the kitchen ring main. what i have realise is if you put a light electrical load on the circuit i.e. a lamp then it will not trip but once you use something that uses a lot of power i.e. microwave it trips straight away. i have checked for loose connections / faulty mcb . do you have any ideas on what could be causing this problem?

thanks in adavance for your replies .

So it's a house you have only just moved in to, has this fault always been present? Do you have a record when the unit has installed?
Is there a socket circuit on the second RCD, that you try plugging the toaster into, if so are he results the same both RCDs trip?
If you turn one of the RCDs off, then use the toaster, does the live RCD still trip?

PrenticeBoyofDerry said:

So it's a house you have only just moved in to, has this fault always been present? Do you have a record when the unit has installed?
Is there a socket circuit on the second RCD, that you try plugging the toaster into, if so are he results the same both RCDs trip?
If you turn one of the RCDs off, then use the toaster, does the live RCD still trip?

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As I understand there is only one RCD, presumably a split load board with protected and unprotected ways, as was the norm in 2000.

sparkwright said:

As I understand there is only one RCD, presumably a split load board with protected and unprotected ways, as was the norm in 2000.

Click to expand...

Think you could be correct.

Therefore I would check firstly if the conducts at the board are not loose and the neutrals have not been shared across loads.

Thanks for the replies but it's a lot more complicated , firstly I just moved in two weeks ago so have not really moved in been using the wall paper stripper and some other tools . The power was not cutting out then . Then last week when I switch on the toaster the power cut out on the rcd circuits.

On the cu there are two sockets circuits on the rcd, on the unprotected side I got the lights , cooker, smoke alarms etc.

When the power cuts out the rcd trips so both socket circuits cut out but the switch on the mcb doesn't trip to indicate if it's on the kitchen or living room circuits .

To figure what circuit was causing the rcd to trip I have isolated the one ring main ,plug in the toaster for the other ring main turn it on . From this I see that the fault is with the kitchen sockets .

I can turn the rcd back on and it will stay on but if I use something with a lot of power if switches off straight away.

I can do basic fault finding as did study electrical engineering at college . But have not got the equipment to do the main tests just a multimeter .

The neutrals are on the correct side so this is not causing the fault .

Hope this makes sense .

The problem will be a neutral earth fault on an RCD protected circuit.

Switching off the MCBs will not eliminate cirucits as the MCB only switches the live

Have a look for anything on the ring circuit which could be affected by damp... a fused spur feeding a shed, washing machine, dishwasher, immersion heater, boiler, fish pond etc. Chances are it will be something suffering water ingress

i did think that water ignress could be a issue as one of the radiators was leaking, not a great start in a new home. only problem now is tracing all the cables under the floor boards as the previous owner has made a lot of modifications to the electrics .

thanks

Maybe just maybe, water ingressed caused by the wall paper stripper!