NTI Short Cycling / Control or Sizing Issue

Boiler short cycles, turning on and off frequently without maintaining steady temperature

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Oversized boiler for load, Incorrect control settings, Faulty thermostat or sensor placement, Low system water volume

How to Fix / Troubleshooting

Safety: Frequent cycling can stress components but is not usually an immediate hazard.

  • Check thermostat: Ensure the room thermostat is not located near heat sources or drafts. Replace if it is malfunctioning.
  • Review settings: On the NTI control, adjust minimum run time, differential, and outdoor reset curve to reduce cycling (refer to manual).
  • Increase water volume: In small systems, adding a buffer tank can reduce cycling; consult a heating professional.
  • Sensor placement: Verify system and outdoor sensors are correctly installed and reading accurately.
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Repair Difficulty

Medium 3/5
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