Your boiler is limiting the temperature of the water being sent to your hot water cylinder, which typically means the water won't get as hot as usual.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: Limitation of cylinder charging temperature in celsius
What causes this fault?
This fault occurs when the boiler detects that it cannot safely heat your hot water cylinder to the requested temperature, often due to a conflict between the boiler's settings and the cylinder's actual heat demand. It is typically caused by a faulty temperature sensor or a thermostat that is sending inaccurate data to the boiler's control board.
DIY fix possible
Locate the hot water temperature dial or digital setting on the boiler control panelAdjust the hot water target temperature slightly to see if the status clearsCheck if the hot water cylinder thermostat is set higher than the boiler's output limit
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like D.78 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.