H02.25 on a Baxi heat pump: ACI error Titan Active System short circuited or on an open circuit
Short answer
On a Baxi heat pump, H02.25 means: ACI error Titan Active System short circuited or on an open circuit. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 2 sources
What it means
On the Assure Split ASHP (AWHP 4.5/6/8 MR + Assure AWHP-IDU 4-8 E)
The manual says: ACI error Titan Active System short circuited or on an open circuit.
Part involved: temperature sensor.
Likely causes:
- Check the connection cable. Check that the anode has not short-circuited and is not broken.
On the HP60 / Baxi Assure HP55 High Temperature Monobloc ASHP (R290)
The manual says: ACI error Titan Active System short-circuited or on an open circuit.
Part involved: temperature sensor.
Likely causes:
- Check the connection cable. Check that the anode has not short-circuited and is not broken.
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.
- 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
- Check the connection cable. Check that the anode has not short-circuited and is not broken.
Who to ask for: heat pump engineer (controls / sensors).
Certification: Manufacturer-trained heat pump engineer.
What you might notice
Sources
- Installation and Service Manual - Air/water 'Split Inverter' heat pump Baxi Assure, Assure AWHP-IDU 4-8 E ↗ · 7762758 - v05 - 19082020 · page 91 · Reviewed 23 September 2026
- Installation, user and service manual - Indoor unit ASHP Control ↗ · 7887625 - v04 - 22072025 · page 128 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026