wrote:

The whole consumer unit is he

http://i250.photobucket.com/albums/g...e/100_1145.jpg

The strip that fails is he

http://i250.photobucket.com/albums/g...e/100_1146.jpg

The button that flips up is on the far left.

OK this makes it clearer. Looks like you have your "split load" consumer
unit built up from two different CUs. With the lower one being RCD
protected and the top one just having a simple switch (which I presume
also cuts power to the whole lower CU as well).

There are a number of circuits on the CU that are known to be potential
causes of trouble: The hob, cooker, & immersion heater. Moving those to
the top CU might be better (you would need to combine a couple of
circuits on the top one to make space since you only have one free way
up there). Having said that there are many people with "whole house"
RCDs feeding many more circuits than that without any problem. So while
an appliance fault is the most likely scenario, don't assume that the
cause of the trip is minor and should be ignored.

Other than that, your best line of approach is following the fault
finding section in the wiki article.

--
Cheers,

John.

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