BoilerFaultCodesYour boiler is not running at its full heating capacity, meaning it may struggle to keep the house warm because it is stuck on a lower heat setting.
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: Heating part load error
What causes this fault?
This occurs when the boiler's internal software has been manually restricted to a lower heat output than what the property actually requires. It is often caused by an incorrect setting during installation or someone accidentally lowering the maximum power limit in the digital menu, preventing the boiler from ramping up to full strength.
This issue is most noticeable during the first cold snap of winter when the boiler is suddenly unable to meet the increased demand for heat.
DIY fix possible
Locate the user control panel on the front of the boilerNavigate to the 'd.0' setting in the installer level (refer to manual)Check if the kW output has been set too low for your property size and increase if necessary
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.0 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.