Triangle Tube Micro-Zoning / Minimum Firing Rate Mismatch

Boiler cycles on and off rapidly when only a small zone is calling for heat

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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

Heating zone too small for boiler minimum output, No buffer tank, Control settings not optimized for small loads

How to Fix / Troubleshooting

Safety: Control adjustments should follow the installation manual. Do not change gas settings.

  • Step 1 – Identify small zones: Determine if a single small radiant loop or a few feet of baseboard are calling alone when cycling occurs.
  • Step 2 – Adjust CH setpoint and differential: On the Triangle Tube control, increase the differential or lower the CH setpoint slightly to reduce cycling.
  • Step 3 – Combine zones (if possible): Temporarily run multiple zones together to increase load and observe if cycling improves.
  • Professional solution: A technician may recommend adding a buffer tank or reconfiguring zoning to better match the boiler’s modulation range.
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Repair Difficulty

Medium 3/5

Required Part

Hydronic Buffer Tank
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