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NTI · Boiler troubleshooting

Stack limit lockout (Lockout 82)

Trinity Tft

What is going on

Flue temperature went past the stack limit.

Likely causes

  • Dirty combustion chamber or heat exchanger
  • Stack limit set wrong
  • Bad stack sensor

Check in this order

  1. Clean the combustion chamber and heat exchanger
  2. Set the stack limit to 220 F (104 C) maximum, or 149 F (65 C) for PVC exhaust in Canada
  3. Compare sensor resistance with the thermistor chart

Applies to: Trinity Tft60, Tft85, Tft110, Tft155, Tft175, Tft200, Tft250, Tft300, Tft399

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Source: NTI Tft60-399 Installation and Operation Instructions (rev. 2012-04-09), Sec. 15.0 Troubleshooting. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.