F.532 on a Vaillant heat pump: Building circuit: Flow rate too low
Short answer
On a Vaillant heat pump, F.532 means: Building circuit: Flow rate too low. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 3 sources
What it means
On the aroTHERM
The manual says: Building circuit: Flow rate too low.
Part involved: Flow rate too low.
Likely causes:
- Heating circuit not fully purged; dirt filter in return missing or blocked; water deficiency; excessive pressure loss; pump cabling defective; pump faulty. Pump fault diagnosis via flow value shown in sensor/actuator test (7000-10000 l/h bands = supply, dry run, electronics, blocked, no PWM).
On the flexoTHERM exclusive (VWF ../4)
The manual says: Building circuit: Flow rate too low.
Part involved: Flow rate too low.
Likely causes:
- Stopcock was not opened; Building circuit pump defective; All consumers in the heating system are closed; Thermostatic valve(s) defective; No bypass valve available in systems without a buffer; Bypass valve incorrectly set or defective; Air in the heat pump; Pump has insufficient output or is defective; Condenser is dirty; Existing dirt filter clogged.
On the geoTHERM mini (VWS 30/4, VWS 36/4.1)
The manual says: Building circuit: Flow rate too low.
Part involved: Flow rate too low.
Likely causes:
- Stopcock was not opened; Building circuit pump defective; All consumers in the heating system are closed; Flow rate is too low for recording with the volume flow sensor (< 120 l/h).
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 - the fault remains displayed until the cause is eliminated.
Manual reset: yes - after the cause is eliminated, press the reset button (indoor unit) or reset via the system control; if it recurs after several resets contact customer service.
What you can check
- Note the full code and text shown on the display (and the date/time it appeared). Check that radiator/underfloor zone valves and thermostatic valves are not all closed and that the system control is calling for heat. Do not keep resetting the unit; report the code to your installer (the operating instructions for this product were not checked for a homeowner reset procedure).
What the engineer will check
On the aroTHERM
- Purge heating circuit; check/clean return dirt filter; check pump cabling and pump; read flow value in sensor/actuator test to diagnose pump condition.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
On the flexoTHERM exclusive (VWF ../4)
- Check the stopcocks, thermostatic valves, bypass valve and dirt filter; Ensure that the flow rate is at least 35% of the nominal flow rate; Check that the building circuit pump functions correctly; Purging the building circuit.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
On the geoTHERM mini (VWS 30/4, VWS 36/4.1)
- Check the stopcocks and thermostatic valves; Ensure that there is a minimum flow rate of 150 l/h; Check that the building circuit pump functions correctly Appendix.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
What you might notice
What owners and engineers report
2 owner and engineer reports mention this.
- No heating on the aroTHERM: 2 reports
Sources
- Installation instructions aroTHERM VWL 55/3 A 230 V, VWL 85/3 A 230 V (GB) ↗ · 0020217827_03 · page VWL ../3 A 0020217827_03 p.33; VWL ../2 A 0020147164_09 p.35 · Reviewed 23 September 2026
- flexoTHERM exclusive VWF 57/4 - 197/4 400V installation and maintenance instructions ↗ · 0020213394_05 · page flexoTHERM 400 V 0020213394_05 p.51; flexoTHERM 230 V 0020213395_04 p.46 · Reviewed 23 September 2026
- geoTHERM mini VWS 36/4.1 230 V installation manual ↗ · 0020250181_00 · page geoTHERM mini 0020250181_00 p.36 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026