D.28 Medium
Your boiler has detected a communication problem or a wiring fault with an external control accessory, such as an additional pump or zone valve.
Technical description: Switching accessory relay 2
Typical repair cost: £100-250 (including labour)
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Protect yourself from future repair bills
A boiler cover plan would cover faults like D.28 — no call-out fees, no surprises.
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Parts commonly replaced
- Wiring harness
- External relay module
- PCB (Printed Circuit Board)
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