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Current draw should only be affecting the cables, the cables should be protected by the breaker. The earth resistance path through the pipe should be low as the pipe is a fair bit of metal.
If you've replaced the CU they should have tested the circuit resistance and importantly the insulation resistance of the wires i.e. is current passing between the conductors or from a conductor to earth because of faulty insulation as that would be a common cause for tripping.
The elements themselves are known to cause tripping because of insulation resistance failure but in this case it's mostly rusting of the element allows water in the tank to connect with a conductor? How often are you replacing thermostats and are they testing faulty when tested? It's pretty simple to test a thermostat.
Airhead-
Thanks for this info, v useful.
Have replaced the element a few years back - old one had no rusting - and the problem has continued at same frequency.
Thermostats replaced every 12-18 months, does seem to be during winter they fail with more frequent use. I’ll look at testing the failed one I’ve just taken out. The pattern is that once they trip, they’ll trip again in a week or so, then more and more frequently, until replaced.
CU has a certificate, and the person who installed cleared up a few other problems in the flat (1970’s build, legacy problems from previous) and this was flagged as an issue to test/address, but has continued since it was done, maybe 3 years ago.
Chopsicle
Any thoughts on this, gratefully received,
I have a hot water immersion tank, for washing up and x2 daily showers and the thermostat (standard 18” with temp dial) keeps tripping until eventually needing replacing. This happens every 12-18 months, and the trip switch thing has evidence of sparking/slight blackening around
Have replaced everything; consumer unit (its on separate ring), heating element, timer, cabling from timer > element, but still keeps happening. ….any ideas what I could do to prevent and stop burning through thermostats?
My only thought is the wiring which hasn’t been replaced, is old in-concrete-wall inside pipe conduit, and is only live (red) + neutral (black) with the pipe it’s run through being the earth. Could the draw of a modern element through older cables be causing this to happen?