Boilerists to the forum…
Grant combi oil boiler – It triggered its overheat lockout after a voltage drop caused the circulation pump to stop.
I could hear water boiling in the heating loop / heat exchanger, and the whole lot was too hot to touch. I let it all cool down and then topped up back to 1 bar, and everything seems normal, but as it’s fairly new I’m wondering if it’s worth getting it checked over?
(Not my boiler but my mum’s, installed a couple of years ago. A fault at the electrical substation caused the voltage to fall to about 140V for a few hours, and unfortunately the boiler fired up to top up its hot water side.)