I will be calling electrician!
But. What's you opinion on this,
Fairly large house , the main fuse box keeps tripping, no individual fuse goes,
But I have to turn all off. Reset then back up one at a time. More often that not it will go again while doing this, but it's not always the same individual fuse that makes it go again.
Wait an hour, and they all flip up. And we have it all working.
We do have lots of extensions, so the two plug sockets in living room have 6 devices plugged in etc.
Sound's like earth fault .. but ..
Think carefully and isolate (unplug) anything with an 'element' or motor in it that is normally plugged in. Isolate and test with cooker before above.
Favorites are hobs, washing machines, dryers.
Can you isolate all outside lighting?
You have isolation for upstairs lights, sockets, downstairs lights, sockets, etc?
Also check with disconnected plugtop transformers .. as these run warm and insulation can break.
Agree with Al. If an RCD keeps tripping, it's most likely an earth fault. Maybe "nuisance tripping" ........... ie freezer/cooker/fridge leaking too much current to earth.
I've also found trips to be faulty, and trip at a lower current than they should.
An electrician (with the correct piece of equipment) should be able to identify the faulty electrical item – but it may take them some time and cost you lots. Therefore if you follow AlBags advice, you should be able to determine the item for yourself. It might take a bit longer, but it will save you money.
One motor to consider is the central heating pump, which could be the culprit.
Can't find any leak Al. Might be under the floor. What I don't understand is .......... if I re-fill to 1.5 bar, it goes down to 0.7 in a few hours and stays there. Surely a leak would keep going?
Have you looked at HW Cylinder and coil to see how old it is?
That is one place that can disappear from system without being seen .. into the domestic hot storage.
I wouldn't think it could be underfloor.