Welton's Local Oil Boiler Installation Specialist

Common boiler fault codes and what usually causes them

Most modern boilers display a fault code on the control panel when they lock out, and while the exact code differs between manufacturers, the underlying causes cluster into a small number of categories: low system pressure (often from a small leak or after bleeding radiators), ignition failure (a worn electrode, gas supply issue, or blocked condensate causing a safety shutdown), or a failed sensor reporting an implausible temperature reading. A condensate blockage or freeze specifically tends to show a distinct code from a genuine ignition fault, which is why checking the external condensate pipe for ice before calling out an engineer in a cold snap can sometimes resolve the issue without a visit at all. We ask for the exact fault code and any recent history — a bled radiator, a cold snap, a recent service — before attending, since it often narrows down the likely cause before we arrive.

What a proper heating quote should include

A quote worth relying on states the specific boiler or equipment model, the labour and materials it covers, whether a system flush and magnetic filter are included, what happens to old equipment removal and disposal, and what's excluded — an unexpected gas pipe upsizing or asbestos-containing material discovered during removal, for example, which can't always be known before work starts. It should also state who's completing the Gas Safe or OFTEC notification and Benchmark commissioning record, since that's the paperwork that protects both the manufacturer's guarantee and the property's compliance history when it's sold. A vague one-line quote makes comparing genuinely different offers difficult, because two prices that look similar can cover very different scopes of actual work.

• Specific make and model, not just "combi boiler"
• Flush and magnetic filter stated as included or excluded
• Old equipment removal and disposal covered
• Notification and Benchmark record responsibility stated

How a condensing boiler recovers extra heat

A condensing boiler passes flue gases through a secondary heat exchanger before they leave the flue, extracting additional heat by condensing water vapour in the exhaust back into liquid, which is expelled as the mildly acidic condensate water down the drain. This is why every condensing boiler needs a condensate drainage route as part of its installation, unlike older non-condensing boilers, which simply vented hot dry gas straight out. The efficiency benefit only fully materialises when the boiler is actually condensing regularly, which needs a return water temperature low enough — generally below 55°C — for water vapour to condense in the first place. A condensing boiler run permanently at a high flow temperature can spend much of its time not actually condensing, which is one of the main reasons flow temperature settings matter as much as the boiler model chosen.

Signs a boiler repair is no longer the right call

A boiler that's failing repeatedly, needing a different part replaced every service, or over roughly ten to fifteen years old is approaching the point where continued repair costs more over time than replacement, particularly once a heat exchanger — the most expensive single part — starts to show signs of failure through leaks or reduced output. Efficiency is the other half of the calculation: an older non-condensing boiler running at 70-80% efficiency against a modern condensing combi at over 90% means a meaningful chunk of every unit of fuel burned in the old boiler is simply lost up the flue. We give a straight answer on repair versus replace based on the fault found and the boiler's age and condition, rather than defaulting to whichever is more profitable to us on the day.

Pumped-oil versus gravity feed: does it matter?

Older oil systems sometimes still rely on gravity feed, where the tank sits higher than the burner and oil flows down to it under its own weight; a pumped system uses the burner's internal pump to draw oil up from a tank at any level, including below the boiler. Gravity feed limits where a tank can be sited and is more prone to airlocks if the line runs dry, while a pumped system is more flexible on tank position but needs the pipe run and lift height kept within the burner pump's rated capacity — usually no more than a few metres of lift and a set maximum run length. When we replace an oil boiler we check which type the existing tank and pipework support before assuming a straight swap, because a tank sited for gravity feed may need repositioning or a different pump to suit a modern burner.

Oil tank de-sludging: why it's not optional

Oil sitting in a tank for years accumulates water from condensation and fine sediment that settles at the bottom, and over time this forms a sludge layer that can be drawn into the fuel line, particularly when the tank is nearly empty and the outlet pulls from lower in the tank than usual. Sludge blocks fine oil filters and burner nozzles, which shows up as burner lockouts or a boiler that won't fire cleanly rather than as an obvious tank problem. De-sludging drains and cleans the tank base without necessarily removing the whole tank, and it's worth doing when a tank is inherited with a property, before switching to a new boiler, or if lockouts recur despite the filter and nozzle being replaced. It's a preventative job that's cheaper done on schedule than after a burner failure it caused.