My Mains fusebox keeps tripping at between 3am and 6am every

[plugwash]

RCBOs are the answer

they are certainly an answer at least for TN systems and possiblly for TT systems where all circuits start from the main board (though i'm dubious about having an unprotected live on the CU busbars in a TT as there is a high chance some idiot will stick a MCB on it) but in a TT with multiple boards its hard to avoid a main RCD (though you can use something like a 300ma or higher type S).

also 1 module rcbos don't tend to isolate the neutral and should therefore be avoided downstream of another RCD.

 

[JohnD]

Yes, but I was thinking about the aggregations of small leakages (SP RCBOs assuming they are P-E not N-E leakage) which individual circuit RCBOs are good for.

The TT would still need an S-type but hopefully you would trap all the leakages on their source circuits so they could be identified and dealt with.



I know I am thought to have an obsession with RCBOs hence the small type

 

[plugwash]

The TT would still need an S-type but hopefully you would trap all the leakages on their source circuits so they could be identified and dealt with.

if the leakage is spread out (e.g. lots of old appliances) then that may well not happen.

having said that he probablly has only 3 socket circuits so if all fixed stuff and lighting can be tested and eliminated then one of (say) 3 30ma rcbos should go before a 100ma type S.

 

[Pensdown]

Because we are dealing with a 100mA RCD I would be very surprised if it was an appliance/all appliances. Also the OP said he has fed all appliances from a 30 and it stayed in.

I think I would bite the bullet and change the RCD. If it still tripped and the fault can't be narrowed down to one circuit then it will may well need a sparks.

 

[securespark]

Trouble is, with an intermittent N/E fault, it is very difficult to track down.

I've been doing testing today, and I've been lucky, because my fault is between L/E, so is isolatable via the MCB's..

I had an RCD intermittently tripping. I auto-tested it from an outlet, and it failed the 1/2 x test.

Testing the RCD in isolation produced perfect results, with 10ms difference between +ve and -ve cycles, as an MEM RCD should be.

So there was something in circuit causing the RCD some grief. Having isolated all the breakers on the board, I switched them back on one by one until a circuit reinstated caused it to fail again. That circuit was a garage CU submain.

Upon isolating all the Garage CU circuits, and establishing that the RCD was testing fine, I switched on the MCB's one by one again until I got a failure.

Have now isolated the fault to an extension ring circuit, and will go back tomorrow to continue investigations.

 

[Pensdown]

If the OP turns all of the MCB's off then he has said the RCD stays in. From that I would rule out a N-E fault?

 

[RF Lighting]

There often needs to be some load on an installation before an RCD will detect a N - E fault.

 

[Pensdown]

Yep, I'd missed that possibility

 

[securespark]

There often needs to be some load on an installation before an RCD will detect a N - E fault.

Not my experience!!

With the circuit MCB off, what happens when you cut simultaneously through N & E?

 

[whistler]

* Can someone explain why the main switch trips and not the individual circuit breakers!!!!!!

Your RCD will trip to an earth leakage which may be a very small current.
The MCD's will only trip when the current exceeds the rating of the mcd.

I'm thinking low temperature (3am to 6am probably coldest part of day!) may be affecting something.


Edit : Sorry only read page 1 of this thread. Didn't relaise there were 5 pages! .The question has of course all ready been answered.

 

[Spark123]

There often needs to be some load on an installation before an RCD will detect a N - E fault.

Not my experience!!

With the circuit MCB off, what happens when you cut simultaneously through N & E?

On a TN-CS with all of the circuits isolated or not drawing power it is possible to short N-E on an RCD protected circuit without tripping the RCD. When enough power is drawn from any of the circuits (RCD side or non-RCD side) the RCD trips.

 

[diablo1952]

There often needs to be some load on an installation before an RCD will detect a N - E fault.

Not my experience!!

With the circuit MCB off, what happens when you cut simultaneously through N & E?

On a TN-CS with all of the circuits isolated or not drawing power it is possible to short N-E on an RCD protected circuit without tripping the RCD. When enough power is drawn from any of the circuits (RCD side or non-RCD side) the RCD trips.

the RCD has not tripped now for a couple of days, we have noticed today that the Microwave is not plugged in so will try this. I have put the 30ma trip on every plud without anything tripping it, so it seems that we have to wait for it to trip again. Have tried a 100w light bulb wired L and E this trips the RCD.Will post a picture when I find the Camera ??
Paul

 

[diablo1952]

To all that assisted me in my RCD problem

It is now cured

This morning aroung 6.30am the RCD tripped
so I tried initially switching it back on ( Did not workk )
So I switched all the MCB's of then switched the RCD on ( It switched on )
then i switched each MCB on and one of them tripped the RCD.
I had marked each MCB so that I knew what was on it.
The MCB was for the Dishwasher/Tumble Drier/Freezer/Washing machine and Fridge Greezer.
I unplugged the all and reset the RCD
When I got to the freezer ( Plugging them in one by one ) it tripped the RCD. When this RCD tripped before it allowed me to reset it afer 60 secs, but this time it was a solid fault.
I will post a picture of the Fuse box when I find the Digital camera.
Your forum is superb and thankyou for all your help , I have picked up many tips from you all.
THANK YOU
Paul

 

[securespark]

Glad you sorted it!!

Just one thing......















What's a

Fridge Greezer.

???