NTI Trinity TFTN 502 — Flame Detected Out of Sequence
502
Flame detected out of sequence. A flame was detected before the gas valve was turned on, so check the flame sensor and its wiring for damage, water, or shorts to ground and replace the PCB if the problem persists. The table classifies it as Auto Reset.
If you smell gas
- Stop what you are doing. Do not use phones, switches, matches or anything that can spark inside.
- Go outside and leave the door open behind you.
- Call the FortisBC 24-hour emergency line at 1-800-663-9911 or dial 911.
Only after that, call ROMA about the boiler. Official guidance: FortisBC gas leaks and odour.
Applies to
This flame fault code is displayed by the NTI HMI control (R30) on TFTN wall-hung models (TFTN085, TFTN110, TFTN150, TFTN199, TFTN285, TFTN340, TFTN399), as documented in TFTN 085–399 Installation and Operation Manual, doc 99987137 V.2025-04-24, section 18.0 Table 18-1 (99987137). Codes can differ between controller generations, so always check the manual that matches your unit.
- NTI Boilers Trinity TFTN
- NTI Trinity TFTN085
- NTI Trinity TFTN110
- NTI Trinity TFTN150
- NTI Trinity TFTN199
- NTI Trinity TFTN285
- NTI Trinity TFTN340
- NTI Trinity TFTN399
- NTI Trinity TFTN500
- NTI Trinity TFTN600
- NTI Trinity TFTN725
- NTI Trinity TFTN850
Controller: NTI HMI control (R30). Source manual: 99987137 (2025-04-24).
Why a code is not a diagnosis
A flame code during operation can come from a blocked condensate or vent path, gas pressure moving out of range, wind at the terminal, or a fouled flame sensor. Only on-site testing identifies the cause.
Safe things to observe
- If you smell gas, stop, go outside and call your gas utility's emergency line or 911 before anything else.
- Note the exact code and what the appliance was doing when it appeared.
- Check whether other gas appliances in the building are working.
Do not
- Do not keep resetting while the cause is unknown.
- Do not touch gas, ignition or combustion components.
How professional service helps
- A technician checks condensate, venting, gas pressure at low and high fire, and combustion readings.
- Combustion and safety devices are verified with an analyser and the manufacturer's procedure after any repair.
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Parts and service
Parts commonly involved
These parts appear in the documented text for this alert. A code reports a condition, not a failed part — a technician confirms the cause by testing before anything is replaced.
Flame sensor (flame rod)
The flame sensor is the small rod that proves a gas boiler's burner is actually lit before the control will keep the gas valve open.
What a technician checks →Gas valve
The gas valve is the boiler's controlled gateway for gas: it opens only when the control has proven safe conditions, meters the fuel to the burner,…
What a technician checks →Control board / PCB
The control board — also called the PCB, or printed circuit board — is the boiler's main computer.
What a technician checks →
Service for this alert
- Gas Boiler Repair
Licensed gas technicians from ROMA Heating & Cooling diagnose and repair residential and light-commercial gas boilers across…
- Emergency Boiler Repair
Priority gas boiler repair for homes and buildings in Greater Vancouver with no heat, no hot water, a locked-out boiler or a leak.
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for NTI Boilers Trinity TFTN.
Frequently asked questions
Does this code mean I have a gas leak?
Not by itself. If you smell gas, stop, leave the building and call your gas utility's emergency line or 911 from outside before anything else. Otherwise the code points to a fault a technician confirms on site.
Can I clear this code myself?
Clearing a code without fixing its cause usually just brings it back. Note the code, check the safe items on this page, then call a licensed technician. If your appliance manual describes a user reset for this exact code and it stays away, no call may be needed.
Boiler locked out? Call with the alert text ready.
The brand, model and this alert are passed along when you request service online, so the technician arrives prepared.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
- TFTN 085–399 Installation and Operation Manual, doc 99987137 V.2025-04-24, section 18.0 Table 18-1 · 99987137 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.