how do you get to 48mm2 ?

Presumably 3off 16mm² - we're told it's tee'd off the supply side of the 1st RCCB in the CU - so if the original internal rat's tails where 16mm² looped through to the 2nd RCCB - then adding another 16mm² brings it up to 48mm² (and probably in an odd shape too).

whether this should be documented as non-compliance with the Electricity Safety, Quality and Continuity Regulations (ESQCR). Would it be appropriate to classify it as (FI), a (C2) defect, or a (C3) defect?

Off the top of my head I don't recall a provision of the ESQCR it would be infringing (unless there was on-site generation, which implies a requirement to meet BS 7671).

Presently, there are no indications of thermal overloading; hence, in accordance with Regulation 433.3.1 (iv), overload protection may be deemed unnecessary due to the fixed load nature of the system

I'd be wary of assuming that just because it hasn't had a major overload so far that it's incapable of doing so in the future, but in general terms yes that regulation might apply (BTW I think it's (ii) in my book rather than (iv)). Really more information is required about the load to be sure either way.  Manufacturer's installation instructions might shed some light too.

Without further information, I'd reluctantly say it would have to be a FI - hence a non-satisfactory, same as C2. Although some extra information (e.g. conductor sizes between RCCB and heater, incl. the c.p.c.) - that should be available to the inspector - might be enough to swing it to a definite C2.

BTW do we know if the 12kW rating is for 230V or 240V?

   - Andy.

how do you get to 48mm2 ?

Presumably 3off 16mm² - we're told it's tee'd off the supply side of the 1st RCCB in the CU - so if the original internal rat's tails where 16mm² looped through to the 2nd RCCB - then adding another 16mm² brings it up to 48mm² (and probably in an odd shape too).

whether this should be documented as non-compliance with the Electricity Safety, Quality and Continuity Regulations (ESQCR). Would it be appropriate to classify it as (FI), a (C2) defect, or a (C3) defect?

Off the top of my head I don't recall a provision of the ESQCR it would be infringing (unless there was on-site generation, which implies a requirement to meet BS 7671).

Presently, there are no indications of thermal overloading; hence, in accordance with Regulation 433.3.1 (iv), overload protection may be deemed unnecessary due to the fixed load nature of the system

I'd be wary of assuming that just because it hasn't had a major overload so far that it's incapable of doing so in the future, but in general terms yes that regulation might apply (BTW I think it's (ii) in my book rather than (iv)). Really more information is required about the load to be sure either way.  Manufacturer's installation instructions might shed some light too.

Without further information, I'd reluctantly say it would have to be a FI - hence a non-satisfactory, same as C2. Although some extra information (e.g. conductor sizes between RCCB and heater, incl. the c.p.c.) - that should be available to the inspector - might be enough to swing it to a definite C2.

BTW do we know if the 12kW rating is for 230V or 240V?

   - Andy.

Hi Andy, must apologize for the current lack of information regarding the voltage rating. Subsequent to a consultation with the client, it has been decided that modifications will be implemented using Henley blocks, accompanied by the installation of an additional two-way consumer unit.