E02.24 on a Baxi heat pump: System flow locking System water flow locking active
Short answer
On a Baxi heat pump, E02.24 means: System flow locking System water flow locking active. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
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: System flow locking System water flow locking active.
Part involved: water flow / pressure.
Likely causes:
- Insufficient flow: open a radiator valve The circuit is clogged: Check that the filters are not obstructed and clean them if necessary. Clean and flush the installation. No circulation: Check that the valves and thermostatic valves are open. Check that the filters are not obstructed. Check that the circulating pump is working. Check the wiring. Check the pump supply: if the pump does not work, replace it. Too much air Completely vent the indoor module and the installation for optimum running. Check that the automatic air vents are properly open (also check the hydroblock). Incorrect wiring: check the electrical connections. Flow meter: Check the electrical connections and the direction of the flow meter (arrow to the right). Replace the flow meter if necessary.
On the HP60 / Baxi Assure HP55 High Temperature Monobloc ASHP (R290)
The manual says: System flow locking System water flow locking active.
Part involved: water flow / pressure.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Remove cause, then acknowledge the error manually on the user interface (engineer).
What you can check
- Note the exact code shown on the controller and when it appeared.
- Read the heating system pressure gauge and report the value to your installer (the manuals quote a minimum of about 1 bar cold).
- Check the filling loop is closed.
- In freezing weather do not leave the system switched off - the manuals warn water faults left unrepaired in winter can let the pump and pipes freeze.
- 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
On the Assure Split ASHP (AWHP 4.5/6/8 MR + Assure AWHP-IDU 4-8 E)
- Insufficient flow: open a radiator valve The circuit is clogged: Check that the filters are not obstructed and clean them if necessary. Clean and flush the installation. No circulation: Check that the valves and thermostatic valves are open. Check that the filters are not obstructed. Check that the circulating pump is working. Check the wiring. Check the pump supply: if the pump does not work, replace it. Too much air Completely vent the indoor module and the installation for optimum running. Check that the automatic air vents are properly open (also check the hydroblock). Incorrect wiring: check the electrical connections. Flow meter: Check the electrical connections and the direction of the flow meter (arrow to the right). Replace the flow meter if necessary.
Who to ask for: heating / heat pump engineer (hydraulics).
Certification: None beyond heating competence (MCS installer recommended).
On the HP60 / Baxi Assure HP55 High Temperature Monobloc ASHP (R290)
- Diagnose per manufacturer service procedure (manual gives description only).
Who to ask for: heating / heat pump engineer (hydraulics).
Certification: None beyond heating competence (MCS installer recommended).
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 93 · Reviewed 23 September 2026
- Installation, user and service manual - Indoor unit ASHP Control ↗ · 7887625 - v04 - 22072025 · page 134 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026