HVACopediaNTI · Boiler troubleshooting
Lockout 138 - flame too low
What is going on
Flame signal drops below what the control needs.
Likely causes
- Blocked venting or air inlet
- Fouled or cracked flame sensor
- Combustion settings off
- Electrical noise on site
- Failing limit in the ILK string
Check in this order
- Check exhaust, air inlet, blower, venturi and heat exchanger for blockage
- Inspect and clean or replace the flame sensor
- Recheck combustion readings
- Look for noisy equipment starting at the same time
- Test the internal low water cutoff and any external limit between R and LIM
Applies to: Trinity Tft60, Tft85, Tft110, Tft154, Tft201, Tft285, Tft340, Tft399
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Source: NTI Trinity Tft399 Installation and Operation Manual (2018-09-07), Sec. 16.0 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.