This question has been debated in the industry over a number of years. There is an answer … but getting to it is not that simple. This IET Wiring Matters article, co-authored by our Managing Director, Graham Kenyon, discusses the matter, and provides a conclusion. Read the article here: https://electrical.theiet.org/wiring-matters/years/2025/107-september-2025/can-a-3-kw-immersion-heater-be-connected-to-a-13-a-fused-connection-unit-to-bs-1363-4/
The subject has also been discussed in eFIXX news:
