H00.48 on a Baxi heat pump: THp Flow Closed Heat pump flow temperature sensor is either shorted or measures a temperature above range
Short answer
On a Baxi heat pump, H00.48 means: THp Flow Closed Heat pump flow temperature sensor is either shorted or measures a temperature above range. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
The manual says: THp Flow Closed Heat pump flow temperature sensor is either shorted or measures a temperature above range.
Part involved: temperature sensor.
Likely causes:
- Check the wiring between the central unit PCB and the sensor. Check that the sensor has been fitted properly. Check the Ohmic value of the sensor. Replace the sensor if necessary.
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 wiring between the central unit PCB and the sensor. Check that the sensor has been fitted properly. Check the Ohmic value of the sensor. Replace the sensor if necessary.
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 89 · Reviewed 23 September 2026
- Installation, user and service manual - Indoor unit ASHP Control ↗ · 7887625 - v04 - 22072025 · page 126 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026