Yes, I think you read the question essentially correctly. Something, assumed to probably be the outside installation, has caused an RCD to operate, taking out the freezer, once last year and once this year, and the OP was asking if there is some device which could prevent an outside fault killing the freezer.
If one were designing from scratch, the solution would obviously be simple enough - simply to arrange things such that the freezer and outside wiring did not share the same RCD/RCBO - either by having them protected by different RCDs or for one of them to have its own RCBO, fed from a non-RCD protected supply. Whether any of those solutions could easily be implemented in the OPs home we don’t know; he was obviously hoping that there would just be some device that could protect the outdoor supply and discriminate reliably against the RCD protecting the freezer etc. - which we are agreed is not possible.
Quite. I don’t think the OP was suggesting that the pump, per se, caused the trip - indeed, there’s no reason why torrential rain should affect something which is already submerged
Rather, I think he was suggesting that other things in the outdoor wiring (switches, JBs) had been affected by the severe rain.Quite so. If it’s only happened twice so far (once during a holiday), the chances of it happening again during a holiday are probably very small - quite probably little/no greater than the risk of the freezer itself failing. As I’ve said before, I seem to have been very ‘lucky’ with RCDs/RCBOs. I have lived with something like 12 of them for many years and there have been few, if any, occasions on which one has tripped without good reason, nor have any of the ‘with good reason’ trips ever happened when the house was unoccupied for a significant period of time.
Kind Regards, John
