D.77 Low
Your boiler is intentionally limiting the amount of power it uses to heat your hot water cylinder, which may result in your water taking longer to heat up than usual.
Technical description: Limitation of cylinder charging in output in kW
Typical repair cost: £0-120 (including labour)
DIY fix possible
Check the hot water temperature settings on the boiler control panelEnsure the cylinder thermostat is not set unnecessarily highMonitor the time it takes for hot water to recover to see if it meets your needs
Protect yourself from future repair bills
A boiler cover plan would cover faults like D.77 — no call-out fees, no surprises.
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Parts commonly replaced
- External hot water controller
- Cylinder thermostat
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