14 on a Stiebel Eltron heat pump: EVE Ex valve will not close
Short answer
On a Stiebel Eltron heat pump, 14 means: EVE Ex valve will not close. The heat pump keeps running with some functions stopped. 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 LWZ 5/8 CS Premium, LWZ 5 S Plus, LWZ 5/8 S Trend, LWZ 5 S Smart (integral ventilation units)
The manual says: EVE Ex valve will not close.
Part involved: compressor or fan inverter.
When it shows: EVE Ex valve will not close.
Likely causes:
- Expansion valve not closing; inverter fuse may have tripped.
On the LWZ 304 SOL / LWZ 404 SOL (integral ventilation units)
The manual says: EVE Ex valve will not close: Expansion valve does not close.
Part involved: compressor / expansion valve / pressure switches.
When it shows: Expansion valve does not close.
Is it safe?
On the LWZ 5/8 CS Premium, LWZ 5 S Plus, LWZ 5/8 S Trend, LWZ 5 S Smart (integral ventilation units)
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: no.
Manual reset: electronics reset button / STB reset per manual.
On the LWZ 304 SOL / LWZ 404 SOL (integral ventilation units)
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: unknown.
Manual reset: unknown.
What you can check
- Note the fault number shown on the programming unit display.
- Check the appliance breakers/MCBs at the consumer unit are on.
What the engineer will check
On the LWZ 5/8 CS Premium, LWZ 5 S Plus, LWZ 5/8 S Trend, LWZ 5 S Smart (integral ventilation units)
- Check the expansion valve is working correctly; reset inverter fuse. Notify your qualified contractor if it recurs.
Who to ask for: Heat pump service engineer (electrical/controls).
Certification: Qualified electrician competence for live-work on appliance electrics.
On the LWZ 304 SOL / LWZ 404 SOL (integral ventilation units)
- Follow remedy in LWZ 304/404 SOL installation manual section 9.4; causes largely parallel LWZ 5-8 list.
Who to ask for: F-gas/refrigeration-qualified heat pump engineer (R290/A3 flammable-refrigerant competence for R290 models).
Certification: F-gas certification for fluorinated refrigerants (R410A/R454C); flammable refrigerant (R290) handling training for R290 models.
What you might notice
Sources
- COMMISSIONING AND NOTIFICATION LIST LWZ 8 CS Premium / LWZ 5 CS Premium / LWZ 5 S Plus / LWZ 8 CS Trend / LWZ 8 S Trend / LWZ 5 S Trend / LWZ 5 S Smart (doc-00081766) ↗ · A 338916-45679-9862 · page 17 · Reviewed 23 September 2026
- INSTALLATION LWZ 304 SOL / LWZ 404 SOL (English, via ManualsLib manual 1279865) ↗ · page 42 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026