D.78 Low
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.
Technical description: Limitation of cylinder charging temperature in celsius
Typical repair cost: £0-120 (including labour)
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
Protect yourself from future repair bills
A boiler cover plan would cover faults like D.78 — no call-out fees, no surprises.
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Parts commonly replaced
- NTC Temperature Sensor
- Cylinder Thermostat
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