Burnham Marginal Venting or Combustion Under High Load

Boiler frequently locks out during very cold weather but runs fine in milder temperatures

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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

Icing at vent termination, Inadequate gas supply pressure under heavy demand, Condensate freezing in drain line, Undersized vent or intake piping

How to Fix / Troubleshooting

Safety first: Turn off power and gas if you suspect vent blockage or combustion issues.

  • Inspect vent termination in cold weather: Check for ice buildup around PVC vent and intake. Clear ice carefully without damaging the pipes.
  • Check condensate drain routing: Ensure the condensate line is pitched properly and protected from freezing. Insulate or reroute if necessary.
  • Monitor gas supply: If other gas appliances also struggle in cold weather, contact the gas utility to check supply pressure.
  • Have vent sizing verified: A technician should confirm that vent and intake sizes and lengths meet Burnham specifications for your model and input.
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Repair Difficulty

Hard 4/5

Required Part

Condensate Trap and Drain
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