Er20 on a Climaveneta / De Longhi Professional heat pump: Differential pressure switch or flow switch tripped; manual reset if active >30 s
Short answer
On a Climaveneta / De Longhi Professional heat pump, Er20 means: Differential pressure switch or flow switch tripped; manual reset if active >30 s. 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 De'Longhi Professional / Climaveneta AWR MTD reverse-cycle air/water heat pump with DHW
The manual says: Differential pressure switch or flow switch tripped; manual reset if active >30 s.
Likely causes:
- Inadequate water flow.
- Air in water circuit.
On the De'Longhi Professional / Climaveneta BWR MTD and MTD2 brine-to-water heat pump
The manual says: Differential pressure switch or system flow switch activated; manual reset if active >30 s.
Likely causes:
- Inadequate water/brine flow, air in circuit, set-point.
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.
What you can check
- Note the code/LED pattern and the model from the rating plate, then contact a heat pump/refrigeration engineer.
- Check the heat pump's breaker/isolator at the consumer unit is on.
- Check the heating system pressure gauge reads in the normal range stated by the installer (usually about 1-1.5 bar cold) and that the filling loop is closed.
What the engineer will check
On the De'Longhi Professional / Climaveneta AWR MTD reverse-cycle air/water heat pump with DHW
- Check water flow.
- Vent air.
- Check electrical connection.
Who to ask for: refrigeration / heat pump engineer.
Certification: Electrical competence for work inside the unit.
On the De'Longhi Professional / Climaveneta BWR MTD and MTD2 brine-to-water heat pump
- Check water/brine flow, air, flow switch wiring, set-point, sensor positions.
Who to ask for: refrigeration / heat pump engineer.
Certification: Electrical competence for work inside the unit.
What you might notice
Sources
- Climaveneta AWR MTD / AWR MTD/B 0011-0061 Installation - Operating - Service Manual (GB 01/2009) ↗ · GB 01/2009 · page 47 · Reviewed 23 September 2026
- Climaveneta WWR MTD - MTD/S, BWR MTD - MTD/S Installation and User Manual (GB 03/2010) ↗ · GB 03/2010 · page 48 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026