DE on a Viessmann Vitotronic 200: Prot.primry pump/fan2: Compressor heat pump stage 2 stops
Short answer
On a Viessmann heat pump, DE means: Prot.primry pump/fan2: Compressor heat pump stage 2 stops. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Prot.primry pump/fan2: Compressor heat pump stage 2 stops.
Part involved: Prot.primry pump/fan2.
When it shows: Compressor heat pump stage 2 stops.
Likely causes:
- Primary circuit fault:.
- Primary circuit pressure switch/frost stat has responded.
- Primary pump thermal relay, heat pump stage 2 (if installed) has responded.
- Phase monitor has recognised a fault.
- Phase monitor faulty.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: Not stated per code; Vitotronic messages remain until the cause is removed and are acknowledged with OK (6150133 p.82). Unremedied acknowledged faults are redisplayed the following day.
Manual reset: Acknowledge with OK on the programming unit (user level permitted per 5817913 p.56-57) after the cause is remedied.
What you can check
- Note the 2-character message code and message text shown on the Vitotronic 200 display (press OK for details) and give them to your heating contractor (operating instructions 5817913 p.56).
- You may acknowledge the message once with OK as described in the Vitotronic 200 operating instructions; if it reappears, do not keep acknowledging it - call your contractor.
- Check the heating system pressure gauge reading and report a low reading to your contractor; make sure the filling loop is closed.
- Check the outdoor unit (air source models) is not blocked by leaves, debris or snow.
What the engineer will check
- Check safety equipment (frost protection brine pressure, frost protection AC-Box) on cross connect PCB, terminals X3.9 and X3.8: See "Cross connect PCB". In systems without ….
- Reset primary source thermal relay. Check primary pump. Replace primary pump if required. The switching signal can be tested at terminal 214.1: See "Main PCB". ….
Who to ask for: Viessmann-trained heat pump installer/service engineer.
Sources
- Service instructions Vitotronic 200 WO1C (5790974 GB, 2023-09) – brine/water & split variants ↗ · 5790974 VSA00002 · page 91 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026