A liquid fuel burner is a simple idea that rewards close reading. It meters fuel, mixes it with air, and lights it, and most field trouble starts on the fuel side rather than inside the combustion chamber. ACHR News's product write-up on the Carlin Combustion Technology EZ-1 Residential Liquid Fuel Burner highlights two features that matter to a homeowner: the unit "combines onboard diagnostics" and offers support for "biofuel blends up to B100." Both features are useful, but only if you know what they mean at your tank and in your basement.
What a blend number tells you
The B number in a biofuel blend is the percentage of biodiesel by volume, with the rest made up of petroleum heating oil. B5 is five percent biodiesel, B20 is twenty percent, and B100 is pure biodiesel. A burner rated for a range of blends is a statement about the parts the manufacturer tested. It is not a promise that every tank of fuel delivered to your house will behave the same way. Read the label or the manual for the approved range, then ask your fuel supplier which blend is actually going into your tank this season.
Where biodiesel changes the job
In general, biodiesel behaves differently from straight heating oil in a few ways that show up at the burner. It is a good solvent, so it can loosen varnish and sludge that has built up in an older tank, lines, and filter housing. That is useful over time, but the loosened material can plug a filter or nozzle sooner than you expect after a switch. Biodiesel also tends to attract and hold water more readily than petroleum fuel, which makes a dry, well-sealed tank more important. Some older rubber gaskets, hoses, and seals can soften or swell when exposed to higher biodiesel content, so check them when you service the burner.
Cold weather is the other factor. Biodiesel generally has a higher cloud point than heating oil, which means it can begin to thicken or wax at temperatures that would not bother a plain petroleum blend. Ask your supplier whether the blend is designed for winter use or whether a cold-flow additive is used. Do not assume that a fuel that starts fine in October will flow at the same rate in January.
Use the diagnostics as a log, not a reset button
Onboard diagnostics are only useful if someone records what they show. When a code appears, write down the code, the date and time, the outdoor temperature, whether the house was calling for heat, and whether the event happened at startup or during a run. Then clear it once and see whether it returns. Repeated resets hide the pattern, and a pattern is what a technician needs. A code that shows up every cold morning and disappears by afternoon points toward a different cause than one that shows up after a fuel delivery.
Keep the log next to the fuel delivery receipts. A simple page with the blend, the delivery date, and any codes or odd noises lets you line up the fuel change with the symptom change. That single page often saves an hour of guessing when the technician arrives.
A practical owner routine
Start by confirming the approved blend range from the burner's documentation and comparing it with what your supplier delivers. Add the filter and nozzle to your seasonal schedule, and check them after the first few tanks of a new blend rather than waiting for a no-heat call. Keep the tank dry, and ask about water testing if the tank has been sitting. Look at the flame through the sight port only if the manufacturer's instructions allow it, and never open fuel lines or work inside the cabinet while the burner is energized.
A multimeter is useful for confirming that the power reaching the burner and controls is what the manual expects, but high-voltage and fuel-side work belongs with a licensed oil heat technician. Your job is to supply the record: blend, delivery, codes, and conditions. The technician's job is to interpret that record against the parts.
Where the roof comes in
Liquid fuel appliances vent through a flue, and a flue that passes through the roof depends on sound flashing and a tight penetration to shed water and keep out wind-driven moisture. If you see staining, a loose collar, or a soft spot around the flue, treat that as a separate job. A roofing contractor such as Keys Roofing can repair the penetration, while the heating service person checks the flue connection and draft. Keeping those two visits distinct makes it easier to know which one fixed the problem.
Further reading: a roofing contractor such as Keys Roofing.