0E99 High
Your boiler system is having trouble talking to the other boilers it works with, which may prevent some or all units from heating properly.
Technical description: Simple cascade communication error
Typical repair cost: £90-250 (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 0E99 — no call-out fees, no surprises.
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Parts commonly replaced
- Communication cable
- PCB (Main Control Board)
- Cascade controller module
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