Navien furnace short cycles: frequently turns on and off with very short run times

Safety: Turn off power before changing internal settings.

• Check thermostat settings: Ensure the thermostat is not set to an extremely tight temperature differential or "adaptive recovery" mode that causes frequent calls. Adjust cycle rate or differential if available.
• Review minimum firing rate: In the installer menu (if accessible), verify that minimum firing rate and anti-short-cycle timers are set according to Navien recommendations. Increase anti-cycle time if allowed.
• Add system water volume (if feasible): For very small radiant or baseboard systems, adding a buffer tank can increase water volume and reduce cycling. This should be designed and installed by a hydronic professional.
• Hydraulic balancing: Ensure all zones have adequate flow and that no single small zone is causing rapid temperature rise. Consider combining small zones or using a buffer tank.