Component
Flame rod (flame sensor)
The rod that proves the burner flame to the control. A dirty or disconnected flame rod produces flame-failure codes even when the burner fires correctly.
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 CANRO about the water heater. Official guidance: FortisBC gas leaks and odour.
Proving the flame
Tankless units must confirm that the burner actually lit before keeping the gas valve open; the flame rod sits in the flame and the control reads the small current through it. A rod that is fouled, coated or disconnected reads no flame, and the unit reports flame-failure even while the burner visibly runs.
Rinnai's RU manual documents the flame-rod checks under code 12 (no flame) and code 52 (gas valve), because a damaged sensing path can mimic both faults; Navien lists the flame rod among its safety devices.
Why cleaning is part of service
Flame rods accumulate combustion deposits and lose sensitivity between services, which is why recurring flame-failure codes on an otherwise healthy unit often clear with the rod cleaned as part of the maintenance visit. Rod replacement follows the manufacturer's checks when cleaning does not restore the signal.
Frequently asked questions
Why does my unit report no flame while the burner is clearly on?
The flame-sensing path is failing: a fouled or disconnected flame rod reads no flame. The manufacturer's checks confirm before the rod is cleaned or replaced.
Is the flame rod the same as the igniter?
No. The igniter lights the burner; the flame rod proves it stayed lit. Both sit in the burner area but serve opposite ends of the ignition sequence.
Request a consultation
CANRO reviews your hot-water demand, equipment and installation constraints. Requests are confirmed by CANRO.
On-site service in Metro Vancouver, BC. Call to check availability.
Related
Sources and verification
- CANRO Heating & Cooling — About · Canadian source · accessed September 7, 2026
- Rinnai RU series Installation and Operation Manual (codes 12 and 52) · 100000467 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.