Miura E-04: Miura EX-300 Error Code E-04

Symptoms

Panel display shows E-04, indicating a flame failure during normal operation. The flame detector has lost the flame signal for more than 4 seconds during main flame operation. The fuel valves have closed and the post-purge cycle has started.

Possible Causes

Dirty or worn burner nozzle causing poor fuel atomization
Flame detector UV sensor lens is dirty or sensor has failed
Gas supply pressure fluctuated below the minimum operating pressure
Combustion air blower not delivering sufficient air for proper combustion

Troubleshooting Steps

Step 1: Inspect and clean or replace the burner nozzle per manufacturer specifications
Verify nozzle capacity (gph or m3/hr) and spray angle match boiler requirements
Step 2: Clean the UV flame sensor lens with a soft lint-free cloth and approved cleaner
Verify sensor output voltage when viewing a test flame is above 2V DC
Step 3: Check gas supply pressure at the burner gas train inlet during operation
Pressure should remain stable at the rated input pressure during firing
Step 4: Verify combustion air blower operation, air inlet filter condition, and damper position
Replace air filter if dirty and verify damper opens fully during firing

How to Reset

To reset E-04: 1) Wait for the post-purge cycle to complete (approximately 20 seconds). 2) On the panel, press the Reset button. 3) The boiler will execute a full pre-purge and ignition sequence. 4) If flame is established and maintained, normal operation resumes. 5) Maximum 3 reset attempts before lockout.

Common Replacement Parts

MI-EX-2001: Miura EX-300 burner nozzle assembly (Verify fuel type and capacity rating before installation)
MI-EX-2005: UV flame detector sensor with mounting hardware (Replace every 2 years or 5000 operating hours)
MI-EX-2010: Combustion air blower motor, 1/2 HP (Lubricate bearings per maintenance schedule)

Frequently Asked Questions

Q: How many times can I reset a flame failure alarm?
The Miura EX controller allows up to 3 reset attempts. After 3 consecutive flame failures, the controller locks out and requires a manual reset by a qualified technician after diagnosing the root cause.
Q: What maintenance prevents flame failures?
Regular cleaning of the burner nozzle, flame sensor lens, and combustion air filter, plus monitoring of gas supply pressure stability, will prevent most flame failure events. Schedule quarterly combustion tuning by a qualified technician.

Miura EX-300 Error Code E-04