NIBE Heat Pump Alarm 51: Low Brine Flow / Low Pressure
Ground loop collector brine pressure or flow rate dropped below minimum safety threshold.
Equipment TypeGround Source / Geothermal Heat PumpBrand: NIBE
Fault SeverityCriticalSystem Lockout Active
Estimated Repair Cost1,200 kr – 3,500 krParts & Certified Labor
🚨 Symptoms of NIBE Error Alarm 51
- Heat pump stops compressor and switches to electric auxiliary heater
- Red alarm indicator on NIBE display with Alarm 51 message
- Higher electricity usage due to backup immersion heater
🔍 Root Causes for NIBE Code Alarm 51
- Low brine fluid level in expansion vessel
- Air lock in collector ground loop
- Brine circulation pump failure or airlock
- Clogged particle filter on brine circuit
🛠️ How to Reset & Troubleshoot NIBE Error Alarm 51
- Check pressure gauge on brine expansion vessel (should be between 0.5 and 1.5 bar)
- Clean the magnetic particle filter on the cold brine return line
- Bleed air from collector loop and top up glycol brine mixture if pressure is low
- Reset alarm in NIBE controller menu
Frequently Asked Questions — NIBE Code Alarm 51
What does NIBE error code Alarm 51 mean?
NIBE code Alarm 51 indicates: Ground loop collector brine pressure or flow rate dropped below minimum safety threshold.
How do I reset error code Alarm 51 on NIBE?
Turn off the electrical circuit breaker or isolator to the unit for at least 5 minutes to discharge the capacitors and reset the microprocessor. If the code reappears immediately upon restarting, professional inspection is required.
What causes error code Alarm 51 on NIBE systems?
Common triggers include: Low brine fluid level in expansion vessel, Air lock in collector ground loop, Brine circulation pump failure or airlock.