Heating engineer advice

JSouthern

Please would any heating experts advise what damage the heating engineer could have caused to our boiler. He isolated the boiler, turning off valves to the heating so that he could decide whether a pressure drop (0.5 bar a week drop) was within the boiler itself, or whether a pipe in the heating system has a leak. He had previously recharged expansion vessel, said pressure valve is dry, and said heat exchanger 'looks' okay.


Trouble is he left the hot water working after the valves were isolated, and told us we could keep using hot water. Within a few hours the pressure was at zero. The water kept working afterwards and the engineer came back a few days later to tell us that the gauge had gone over the top because the hot water had caused the pressure in the boiler to rise too high. (Nowhere to put the excess heat from HW as the central heating was isolated). A few blogs say the hot water shouldn't be used in this situation. We used HW 5 days while isolated. My query is - what harm will this have caused the boiler apart from it needing a new pressure gauge on.

Water and heating are now both off for another 4 days, boiler is isolated with red tape on it saying do not use, until he comes back to see whether the pressure in the boiler drops again. (He has fitted a new gauge and repressurised the isolated boiler to 2). What problems might he have caused by the hot water overheating to the extent that the gauge went over the top and broke... in case he says we now have more faulty parts in addition to pressure dropping. Knowledgeable advice greatly appreciated. Thank you. Jan