Triangle Tube Short Cycling / Control or Sizing Issue

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

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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 (outdoor reset, differential), Flow too low through boiler, Faulty temperature sensor causing rapid shutoff

How to Fix / Troubleshooting

Safety: Adjust only user-accessible settings unless you are qualified. Do not alter gas settings.

  • Step 1 – Check thermostat and setpoints: Ensure thermostats are not set with extremely tight differentials. On the Triangle Tube control, review CH setpoint and differential settings per the manual.
  • Step 2 – Verify flow: Confirm that all relevant zones are open and the circulator is running. Closed valves or low flow can cause rapid temperature rise and shutdown.
  • Step 3 – Outdoor reset curve: If equipped, review the outdoor reset curve. A very high curve can cause overshooting and short cycling. Adjust to recommended values.
  • Step 4 – Professional assessment: If short cycling persists, a technician should evaluate boiler sizing, buffer tank options, and sensor accuracy.
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Repair Difficulty

Medium 3/5

Required Part

Supply NTC Temperature Sensor
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