11 on a Stiebel Eltron heat pump: Low pressure sensor: The low pressure sensor does not deliver a plausible signal (< 2 mA for longer than 10 s). The heat pump is blocked in cooling mode
Short answer
On a Stiebel Eltron heat pump, 11 means: Low pressure sensor: The low pressure sensor does not deliver a plausible signal (< 2 mA for longer than 10 s). The heat pump is blocked in cooling mode. 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: Low pressure sensor: The low pressure sensor does not deliver a plausible signal (< 2 mA for longer than 10 s). The heat pump is blocked in cooling mode.
Part involved: temperature/pressure sensor.
When it shows: The low pressure sensor does not deliver a plausible signal (< 2 mA for longer than 10 s). The heat pump is blocked in cooling mode.
Likely causes:
- Low pressure sensor fault or sensor lead.
On the LWZ 304 SOL / LWZ 404 SOL (integral ventilation units)
The manual says: Low pressure sensor: Low pressure sensor does not deliver a plausible signal (< 2 mA for longer than 10 s).
Part involved: temperature/pressure sensor.
When it shows: Low pressure sensor does not deliver a plausible signal (< 2 mA for longer than 10 s).
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: unknown.
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 sensor lead. If the fault recurs, inform your qualified contractor.
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: Heat pump service engineer (electrical/controls).
Certification: Qualified electrician competence for live-work on appliance electrics.
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