NTI Trinity TRX 3 09 — Flame Detection While Burner is Off
3 09
Flame detection while burner is off. The boiler blocked because a flame was detected while the burner was off; likely causes are a damaged flame probe or its wire, water damage, a flooded combustion chamber after a blocked condensate drain, or a PCB internal fault. The table classifies it as Blocking (Manual Reset).
Applies to
This venting or air-supply fault code is displayed by the TRX Series II control on TRX Series II models from 150 up to 199C (TRX150, TRX199, TRX199C), as documented in TRX Series II 150–199C Installation and Operation Manual, doc 420012001300 Rev 05, Part 13-B Boiler Error Codes (420012001300 Rev 05). Codes can differ between controller generations, so always check the manual that matches your unit.
- NTI Boilers Trinity TRX
- NTI Trinity TRX085
- NTI Trinity TRX120
- NTI Trinity TRX150
- NTI Trinity TRX199
- NTI Trinity TRX110C
- NTI Trinity TRX150C
- NTI Trinity TRX199C
Controller: TRX Series II control. Source manual: 420012001300 Rev 05 (2024-06-18).
Why a code is not a diagnosis
A venting or air-supply code points at the combustion-air path: a blocked terminal, a restricted flue, a failed fan, or a condensate restriction. It does not say which, and running an appliance with a blocked flue is unsafe.
Safe things to observe
- If a carbon-monoxide alarm sounds anywhere in the building, leave immediately and call 911 from outside.
- From a safe distance, check that the vent terminal and combustion-air inlet are not blocked.
- Do not run the appliance while a blockage is suspected.
Do not
- Do not put anything into the vent or air-intake openings.
- Do not remove or modify vent pipe.
How professional service helps
- A technician inspects the full vent and combustion-air path, clears blockages and checks the fan.
- 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 →Burner assembly
The burner assembly is where gas and air meet and burn inside a boiler, and its condition decides whether combustion is clean or makes carbon…
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 →Condensate trap
Every condensing boiler makes acidic water as it cools its flue gases, and the condensate trap collects that water and seals the flue gases out of…
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…
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for NTI Boilers Trinity TRX.
Frequently asked questions
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
- TRX Series II 150–199C Installation and Operation Manual, doc 420012001300 Rev 05, Part 13-B Boiler Error Codes · 420012001300 Rev 05 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.