9Kw pool heater, earth rod, seasonal drought + total tiling

[Ace1]

My neighbour had a 9Kw inline (in-pipe) water heater fitted - cables look well installed, with trip protection as requested by the heater installers.
On connection it pulled the house trip.
They suggested (rightly or wrongly) to install a separate supply before the house distribution panel - this was carried out by an electrician.
They returned when the owner was absent, re-installed the heater, and apparently the trip pulled, but it's not clear cos there were no witnesses - but they left with the heater.
1 year later they are to return (job has been paid for - ouch!)

Clearly the heater itself could have been duff.
However, I'd be interested to learn your thoughts on whether a 'bad earth' could be responsible, due to the fact that:
1. They only have one rod (and no transformer connection - TT)
2. It's fitted in-house (and tiled over ie. only entry cable is visible)
3. The entire garden/enclosed courtyard is tiled (water drained away)
4. We suffer seasonal drought

Having spent some time researching this (to get an overview), it appears(?) that a bad earth could cause tripping, but could also prevent tripping, depending on the protection used.

Time to get some firm advice from the community, in order to inform him of both the general risks/problems of a bad earth - the risk that a short could electrify the pool - and the possibility (or not) that the earth can't take the 9Kw connection, so causing the trips.

Note: there is no available surrounding land for multiple test stake testing.

 

[Engineer54]

Haha!! ... I think i know what you mean, but having that problem ''every'' time you do a rod install must be a real downer for you sparks out there!!! Ever tried using a rod enhancers?? I think a Bentonite slurry might be your best choice in an non-compacted sand situation, maybe with some further enhancing chemicals if you don't have any water table catchment situations to worry about.... Just a thought!!!