D.20 Low
Your boiler has reached the maximum allowed temperature for heating your hot water cylinder and is pausing operation as a standard safety limit.
Technical description: Maximum set value for target cylinder
Typical repair cost: £0 (including labour)
DIY fix possible
Check the hot water temperature setting on the boiler control panelReduce the target cylinder temperature if it is set unnecessarily highWait for the system to cool down naturally before the boiler resumes
Protect yourself from future repair bills
A boiler cover plan would cover faults like D.20 — no call-out fees, no surprises.
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