How much does it cost to fix Navien error code E787?

Typical repair cost for the Navien E787 fault is £120-250 including labour.

E787 High

Navien E787 Fault Code

Q: What does the Navien E787 fault code mean?

Your boiler's electronic control system has encountered a temporary processing glitch and has locked itself out to prevent any potential issues.

The Navien E787 fault code means: your boiler's electronic control system has encountered a temporary processing glitch and has locked itself out to prevent any potential issues.. It appears on 8 Navien models in our database.

Technical description: Abnormal operation: Reset device

Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Navien models that show the E787 fault code

Click a model for the full fault code list and model-specific repair notes.

LCB700 Repair: £120-250
NCB Repair: £100-200
NCB 28 HE Repair: £90-180
NCB 35 HE Repair: £90-180
NCB 40 HE Repair: £90-180
NCB CE Repair: £120-250
NCB H Repair: £90-180
NHB 29 Repair: £90-180

Source

Navien E787 fault code information on this page is sourced and cross-checked against the official Navien service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026