F.715 on a Vaillant heat pump: Env. circuit: Fault contact: Pump open
Short answer
On a Vaillant heat pump, F.715 means: Env. circuit: Fault contact: Pump open. The heat pump stops until the fault clears or is reset. 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 flexoTHERM exclusive (VWF ../4)
The manual says: Env. circuit: Fault contact: Pump open.
Part involved: Fault contact: Pump open.
Likely causes:
- The electronics system of the high-efficiency pump has detected a fault (e.g. dry running, blockage, overvoltage, undervoltage) and has switched off and locked the pump; Air in the environment circuit; Brine fluid viscosity is too high.
On the geoTHERM mini (VWS 30/4, VWS 36/4.1)
The manual says: Environment circuit: Fault contact, pump open.
Part involved: Fault contact, pump open.
Likely causes:
- The electronics of the high-efficiency pump has detected a fault (e. g. dry running, blockage, overvoltage, undervoltage) and switched the pump off as a securing measure.
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). Contact your installer or Vaillant Service; do not attempt any repair.
What the engineer will check
On the flexoTHERM exclusive (VWF ../4)
- Switch the heat pump off for at least 30 seconds (no current); Check the quality of the plug contact on the PCB; Check that the pump functions correctly; Purge the environment circuit; Use a refractometer to check the mixture ratio of the brine fluid; Check the dirt filter/strainer for dirt; Check the air separator.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS ground-source installer; F-gas certificate for refrigerant work.
On the geoTHERM mini (VWS 30/4, VWS 36/4.1)
- Switch the heat pump off for at least 30 seconds (no current); Check the quality of the plug contact on the PCB; Check that the pump functions correctly; Purging the environment circuit Appendix.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS ground-source installer; F-gas certificate for refrigerant work.
What you might notice
Sources
- flexoTHERM exclusive VWF 57/4 - 197/4 400V installation and maintenance instructions ↗ · 0020213394_05 · page flexoTHERM 400 V 0020213394_05 p.52; flexoTHERM 230 V 0020213395_04 p.47 · Reviewed 23 September 2026
- geoTHERM mini VWS 36/4.1 230 V installation manual ↗ · 0020250181_00 · page geoTHERM mini 0020250181_00 p.37 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026