29 on a Vaillant geoTHERM: Coolant pressure outside the range
Short answer
On a Vaillant heat pump, 29 means: Coolant pressure outside the range. The heat pump keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Coolant pressure outside the range.
Part involved: Coolant pressure outside the range.
When it shows: Temporary shutdown: compressor stops, heat pump remains in operation; becomes a fault-induced shutdown (60/62/81/83/84) if it occurs three times in a row.
Likely causes:
- Refrigerant pressure too high or too low - all causes of errors 27 and 28.
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 - compressor restarts automatically after 5 min (60 min after errors 27/29) once the cause is removed.
Manual reset: not required.
What you can check
- Note the full code and text shown on the display (and the date/time it appeared). The geoTHERM operating manual says: do not attempt to remove the source of the malfunction yourself; only an expert technician can remedy the fault and reset the error code. Warnings (26, 36) and temporary faults can be noted and discussed at the next inspection.
What the engineer will check
- See errors 27 and 28; if it occurs twice in a row the heat pump cannot restart for 60 min.
Who to ask for: F-gas certified refrigeration engineer with heat pump experience (R290 flammable-refrigerant competence required for aroTHERM plus / GeniaAir).
Certification: F-gas Category I (Regulation (EU) 517/2014 as retained in GB) certificate; flammable (R290) refrigerant training for R290 units.
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- No heating on the geoTHERM (VWS/VWW ../2, VWS ../3): 1 report
Sources
- Installation instructions geoTHERM VWS 6-10kW 230V (GB 08/2008) ↗ · 0020046310_01 · page geoTHERM VWS 6-10 kW 230 V 0020046310_01 p.73; geoTHERM VWS/VWW 6-17 kW 400 V 0020057444_01 p.71; geoTHERM VWS/VWW 22-46 kW 0020051574_04 p.101; geoTHERM exclusive operating manual 0020071929_00 p.26 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026