This is the paperwork for said shower, I can't see anything about boilers, combi or not ??? https://www.dropbox.com/s/1oysj8fn8rrj3su/1060736_w2_f_mira_sport_max_10.8_kw.pdf
I once made this mistake. Turned the electric shower on and the combi boiler came on at the same time! The hot water flow from the electric shower was brilliant !!!!! (kept it to just myself and the electrician). Tappy,
Yeah - 'cos you didn't want to land yourselves in very hot w... ok, I'll stop there . @@@tumbleweed@@@