505 on a Mitsubishi Heavy Industries Air-Conditioning Europe Hydrolution: Inverter has earth fault: Inverter has earth fault

What it means

The manual says: Inverter has earth fault: Inverter has earth fault.

Part involved: Inverter has earth fault.

When it shows: Inverter has earth fault.

Likely causes:

• Check connections.

Is it safe?

The heat pump keeps running with some functions stopped.

Resetting itself: yes.

Manual reset: yes (select 'reset alarm' in the alarm menu).

What you can check

• Note the alarm number/text shown on the display. Check the consumer-unit breakers/isolators for the indoor and outdoor units are on. Check the outdoor unit is not blocked by leaves, snow or ice and its drain is clear (look only - do not open the casing). On the RC-HY controller you may select 'reset alarm' once (installation manual: 'in most cases it is enough'); if the red lamp stays or the alarm returns, select 'aid mode' (if enabled) or 'add. heat only' in menu 4.2 and contact the installer.

What the engineer will check

• Per manual 'May be due to': Check connections. Check sensor wiring/resistance, settings, flow (particle filter, pump) and supply as applicable.

Who to ask for: Heat pump / refrigeration engineer (manufacturer-trained).

Certification: F-gas certification for refrigerant-circuit work; electrical competence (Part P/18th Edition) for PCB/wiring.

What you might notice

• Status lamp changes from green to red; alarm bell in display; Automatic reset once no active earth fault has been sent for 60 seconds

Sources

• Installation Manual - Air to Water Heat Pump using R32 refrigerant, Hydrolution (HM) ↗ · PSC012D169 (202201) · page PDF p.85 (printed 83) · Reviewed 23 September 2026

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

Reviewed: 23 September 2026