H06.77 on a Baxi HP60 / Baxi Assure HP55 High Temperature Monobloc ASHP: ODU EEPROM error EEPROM error in hydronic system main control board in the outdoor unit
Short answer
On a Baxi heat pump, H06.77 means: ODU EEPROM error EEPROM error in hydronic system main control board in the outdoor unit. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: ODU EEPROM error EEPROM error in hydronic system main control board in the outdoor unit.
Part involved: power supply / PCB.
Likely causes:
- The EEprom parameter is incorrect. Rewrite the EEprom data. The EEprom chip is broken. Replace it with a new EEprom chip. The main control PCB for the hydraulic module is broken. Replace it with a new PCB.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - system restarts automatically when the cause disappears (may run in degraded/back-up mode meanwhile).
Manual reset: not required once cause removed.
What you can check
- Note the exact code shown on the controller and when it appeared.
- Check the heat pump's consumer-unit breaker / isolator is on (do not open any panels).
- The manual's user steps allow switching the system off and on once to see if the error clears; if the code returns, contact the installer.
- If the code persists or returns, contact a heat pump engineer.
What the engineer will check
- The EEprom parameter is incorrect. Rewrite the EEprom data. The EEprom chip is broken. Replace it with a new EEprom chip. The main control PCB for the hydraulic module is broken. Replace it with a new PCB.
Who to ask for: heat pump engineer with electrical competence.
Certification: Qualified electrician / manufacturer-trained heat pump engineer; F-gas if refrigerant circuit is opened.
What you might notice
Sources
- Installation, user and service manual - Indoor unit ASHP Control ↗ · 7887625 - v04 - 22072025 · page 133 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026