027 on an iDM Energiesysteme TERRA SW: Flow lockout / pressure monitoring - lockout: The flow switch on groundwater systems has switched the heat pump off (> 3 times in 24 h). The heat pump is no longer operated

What it means

The manual says: Flow lockout / pressure monitoring - lockout: The flow switch on groundwater systems has switched the heat pump off (> 3 times in 24 h). The heat pump is no longer operated.

Part involved: Flow lockout / pressure monitoring - lockout.

When it shows: The flow switch on groundwater systems has switched the heat pump off (> 3 times in 24 h). The heat pump is no longer operated.

Is it safe?

The heat pump stops until the fault clears or is reset.

Manual reset: Unlock/acknowledge via Navigator (max. once after 023); call service.

What you can check

• Note the fault number and text shown after tapping the fault symbol on the Navigator display. Look at the brine/heat-source expansion vessel or pressure gauge: the fluid level should be visible (user guide check). Do not refill or open the ground-loop circuit yourself - call the installer. This is a locking (Verriegelung) fault - iDM says to call customer service; do not repeatedly unlock it (after fault 023 the unit may be unlocked at most once).

What the engineer will check

• Diagnose per iDM service documentation for the unit (not obtained): check the monitored circuit/component named in the fault.

Who to ask for: heat pump engineer.

Certification: F-Gas category I certificate (refrigerant circuit work).

What you might notice

• Fault symbol in the Navigator 2.0 command bar; fault message shown in red when selected

Sources

• IDM Wärmepumpen mit Navigatorregelung 2.0 - Bedienungsanleitung (812152 Rev.3) ↗ · 812152 Rev.3 · page p.70 · Reviewed 23 September 2026

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026