Chimney care
Keeping the UNI 60 flue safe and drawing — sweeping frequency, acidic condensation, joint deterioration and what changes the deposition rate.
Flue gas creates soot and condensation that lead to deterioration of joints — so chimney maintenance is a safety task, not just a draft task. For safe and efficient operation of the boiler it is necessary to ensure the chimney is swept.
What "good" looks like
The inside of the chimney should be smooth, without a condensation or soot deposit zone, for optimal draft without obstruction.
Check for:
- soot and tar build-up narrowing the bore;
- condensation staining at joints and bends;
- corrosion at the joints — the first place acidic condensate attacks;
- any obstruction: nests, debris, collapsed liner.
What changes the deposition rate
| Factor | Effect |
|---|---|
| Fuel type | Wood deposits more than coal |
| Boiler temperature | Lower temperatures condense more tar |
| Operation mode | Long, air-starved burns deposit far more than hot, clean burns |
| Fuel moisture | Wet fuel is the single biggest contributor |
| Chimney insulation | An exposed, uninsulated flue runs cold and condenses |
| Number of bends | Each bend costs draft and collects deposits |
The efficiency link
Soot and ash deposits on the walls reduce heat transfer and efficiency. A fouled chimney and a fouled heat exchanger usually arrive together, and both trace back to the same cause: burning wet wood, or running the boiler too cool.
Choosing a chimney for maintainability
When choosing a chimney, consider:
- compatibility with the boiler;
- the type of fuel;
- ease of assembly and disassembly for maintenance;
- and compliance with fire safety standards.
The number of chimney bends should be as small as possible.
Specification requirements are on Chimney requirements: 8 in minimum, stainless steel 316 acid-resistant, single wall in a brick channel, double-walled insulated if exposed, to EN 1856-1:2013 and EN 1856-2:2013.
Checking draft
Present a strip of paper to the ash pit — the strip should deviate to the side of the ash pit.
Also confirm that the ventilation openings for inflow and exhaust have not been restricted or blocked.
If draft is poor:
| Cause | Fix |
|---|---|
| Cold chimney | Insulate exposed runs; use a chimney fan on start-up |
| Soot narrowing the bore | Sweep |
| Too many bends | Re-route if possible |
| Blocked ventilation openings | Clear them — the boiler needs combustion air |
| Undersized flue | Must be at least the boiler outlet diameter — 8 in |
Start-up smoke
For best comfort and minimal fume migration in the house, use a chimney fan upon starting the boiler. As a second option, smoke hoods.
Keep the records
Maintain documentation of clearance distances and code compliance for insurance and reference purposes. Add your sweeping records to the same file.
Fuse, sensors, consumables, and when to call MBtek.
Cleaning the boiler
How to clean a UNI 60 — ash removal, scraping the furnace and loading chamber, clearing the combustion air ducts and brushing the heat exchanger.
Parts and service
Replacing the TIS Tronic 260U fuse and sensors, the consumables not covered by warranty, and when a job must go to an accredited service centre.