Applicable Systems
EX-300
Symptoms
Panel display shows E-08, indicating a high exhaust gas temperature alarm. The exhaust temperature sensor has exceeded the setpoint of 260C (500F), triggering a shutdown to protect the boiler pressure vessel and heat transfer surfaces.
Possible Causes
- Fouled heat transfer tubes reducing heat absorption from combustion gases
- Excess combustion air causing high stack temperature and efficiency loss
- Boiler operating above rated capacity due to demand spikes
- Feedwater temperature too low, increasing temperature differential across tubes
Troubleshooting Steps
- Step 1: Inspect and clean the boiler fire tubes - remove soot and scale buildup
Use rotary tube cleaner or high-pressure water jet per manufacturer method - Step 2: Perform combustion analysis and adjust air-to-fuel ratio
O2 in exhaust should be 3-5% for gas firing, CO2 should be 8-9% for gas - Step 3: Verify boiler is not firing above rated input capacity
Check firing rate control and fuel input against nameplate - Step 4: Check economizer or feedwater heater operation if equipped
Verify feedwater temperature entering boiler is at design value
How to Reset
To reset E-08: 1) Allow the exhaust temperature to drop below 200C (392F). 2) On the panel, acknowledge the alarm. 3) Press the Reset button. 4) The boiler restarts with normal pre-purge and ignition sequence.
Common Replacement Parts
- MI-EX-3001: Exhaust temperature thermocouple Type K, Miura EX-300 (Verify calibration against reference thermometer)
- MI-EX-3005: Tube cleaning brush set, carbon steel (Use correct diameter for tube size)
- MI-EX-3010: Combustion analyzer service kit (Calibrate analyzer before use per manufacturer)
Frequently Asked Questions
- Q: How often should boiler tubes be cleaned?
For gas-fired Miura boilers, inspect and clean tubes every 6 months or when exhaust temperature rises 25C (45F) above the baseline reading established at commissioning. For oil-fired boilers, clean every 3 months.
- Q: What is the ideal exhaust gas temperature?
For a properly tuned gas-fired Miura EX-300, exhaust gas temperature should be 150-200C (300-392F) at full load. Temperatures above 230C (446F) indicate fouled tubes or excess combustion air and require attention.
Comments (0)
Share your experience to help others facing the same problem.
Leave a Comment
Source: Miura EX Series Boiler Installation and Operation Manual, Form IOM-EX-300
Category: Boiler
No comments yet. Be the first to share your experience!