A. O. Smith Burkay 4 — Flame Sensed Out of Sequence
4
Flame sensed out of sequence. Next system action: If situation self corrects within 10 seconds, control returns to normal sequence. If flame out of sequence remains longer than 10 seconds, control goes to Flash code 6+4 (see below). Recommended service action: Check for pilot flame. Replace gas control valve if pilot flame is present. If no pilot flame, cycle "Call for Heat." If error repeats, replace control. The table classifies it as Green LED status code (continuous retry models C, M, E and K).
Applies to
This fault code is displayed by the Honeywell intermittent ignition control (yellow flame LED and green status LED) on Burkay HW models (HW-300, HW-399, HW-420, HW-520 and HW-670), as documented in A. O. Smith Burkay Gas Fired Commercial Copper Boilers User Manual, Models HW 300, 399, 420, 520, 670, doc 100077928, Tables 4-6 (100077928). Codes can differ between controller generations, so always check the manual that matches your unit.
- A. O. Smith Conservationist Burkay (hot-water boilers)
- A. O. Smith Burkay HW-300
- A. O. Smith Burkay HW-399
- A. O. Smith Burkay HW-420
- A. O. Smith Burkay HW-520
- A. O. Smith Burkay HW-670
Controller: Honeywell intermittent ignition control (yellow flame LED and green status LED). Source manual: 100077928.
Why a code is not a diagnosis
The code reports the condition the control detected; the underlying cause must be confirmed on site by a licensed technician using the manufacturer's procedure.
Safe things to observe
- Note the exact code, when it appears and what the appliance was doing.
- If the appliance has stopped, call a technician rather than repeatedly restarting it.
- If you smell gas, stop, go outside and call your gas utility's emergency line or 911 before anything else.
Do not
- Do not ignore a code that returns after a reset.
How professional service helps
- A licensed technician diagnoses the cause with the manufacturer's test procedure.
- 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.
Pilot assembly
A pilot assembly is the small burner, orifice, igniter and flame sensor that lights the main burner on older gas boilers.
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 →
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 A. O. Smith Conservationist Burkay (hot-water boilers).
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
- A. O. Smith Burkay Gas Fired Commercial Copper Boilers User Manual, Models HW 300, 399, 420, 520, 670, doc 100077928, Tables 4-6 · 100077928 · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.