HVACopediaNTI · Boiler · Ignition
Light-off sequence and retries
What happens, in order
- Call for heat is present and limits are closed
- Blower drives up to light-off speed; Hold 62 appears momentarily and is normal at this point
- Combustion blower purges the heat exchanger
- Spark generator gets 120 VAC and the igniter arcs; the control also sends 24 VAC to the gas valve (trial for ignition)
- Flame rod must prove flame; if proven the burner runs and modulates
- If flame is not proven the trial ends with a post-purge and the control tries again
- After three trials without flame the control stops with Hold 110 (Lockout 109 ignition failed)
- If fan speed is not proved for more than 15 s the control stays on Hold 62
- Flame lost during the main flame establishing period: Lockout 106; lost early in the run: Lockout 107; lost later in the run: Lockout 108
- Weak flame signal Lockout 138, or Alert 449 when the control just raises minimum fan speed for a while
Timings and thresholds
| Item | Value |
|---|---|
| Ignition trials before stopping | 3 (built-in retry) |
| Cycles seen at commissioning test with flame wire unplugged | 4 ignition cycles, then Hold 110 |
| Hold 62 before light-off | Momentary; investigate at 15 s or more |
| Spark voltage | About 14,000 V |
Codes you may see during this
Hold 62 Hold 110 Lockout 109 Lockout 106 Lockout 107 Lockout 108 Lockout 138 Alert 449
Applies to: Trinity Tft60, Tft85, Tft110, Tft155, Tft175, Tft200, Tft250, Tft300, Tft399
Models
More NTI boiler sequences
- Combustion checking procedure · Startup
- Power-on and mode sequence · Startup
- Power-up and what lets the boiler start a call · Startup
- Failed ignition and lockout · Ignition
- First ignition start-up · Ignition
- Central heat call (CH1) from call to satisfied · Heating
- Indirect tank (DHW) call · Domestic hot water
- Circulator outputs and their fuses · Pump/purge
Related
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Source: NTI Tft60-399 Installation and Operation Instructions (rev. 2012-04-09), Sec. 8.0 Lighting, Sec. 10.0 Piping, Sec. 15.0 Troubleshooting. Written in our own words; timings can differ by model and software version, so check the manual for your exact unit.
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.