H1 displayed during heating; outdoor unit may frost heavily

Note: On many SMEG heat pump models, H1 is an informational code indicating defrost mode, not a fault.

• Allow defrost cycle: Wait 5–15 minutes. The unit should resume normal heating automatically.
• Check outdoor coil cleanliness: If defrost cycles are very frequent, clean the outdoor coil to improve heat exchange.
• Observe ambient conditions: In very cold, humid weather, frequent defrost is normal.
• Sensor check: If H1 persists and heating is poor, the outdoor coil sensor may be faulty and require replacement.

If the unit never exits H1 or does not heat, contact a technician to verify sensor readings and defrost control.