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Posted on: 16/11/2018

Shorter AGA service intervals? CPS Fuels Information Sheet

Are you experiencing shorter service intervals with your AGA?

The national print, radio, and in some instances television have recently been reporting on a problem concerning AGA type cookers (vapourising burners). For years it has been implied that the shorter service intervals may be a regional or even national problem, but the focus has nearly always been on supply, rather than the applicence, but could the “problem” have a very simple solution?

White Oil Aga

The by-product, carbon, is produced when heating oil (kerosene) vaporises from its liquid form into a gaseous state. This process is known as “cracking”, and it begins from the moment the burner is ignited. Over time a black carbon deposit can build up with the older designs of cooker often more prone than the modern equivalents.

Due to high call out charges, or increased annual maintenance contract costs, aga owners have sought and found, or found and shared free or low cost DIY solutions and fixes, on websites, forums, and blogs. Despite many reports and rumours about the cause of this particular problem, often called the Aga saga, there can only ever be two problems that will actually affect the combustion process.

The appliance and it’s installation:

Firstly, check the condition of your flue (the exhaust duct for smoke and waste gases). You may have recently had your flue cowl replaced with that of a different design, there may be a restriction blocking the chimney such as tree branches or the erection of a new building. If the area around the flue has been changed in any way, it could seriously affect the climatic conditions enjoyed by your cooker, which in turn will affect the combustion and the temperature around the burner and carbon leg. If the fuel vaporises in the carbon leg, carbon will “crack” prematurely and form here instead of the correct area (the vaporising chamber of the burner) and will only need a piece of carbon the size of an apple seed to cause a blockage whereas a teaspoon full formed in the correct place would not have any affect. A taller chimney is advantageous over a shorter one as the higher the flue pull, the cooler the carbon leg is kept, meaning it is less likely to create a gathering of carbon in the wrong place. The downside to having a higher chimney is that you might use more fuel to maintain oven temperatures.

The oil supply being burned by the appliance:

The second element to check is the more commonly blamed problem; fuel and by inference it’s quality. Since the early 80’s there has been a problem with premature carboning with vaporising burners. Although the oil companies have regularly been blamed for providing “dirty oil” to customers, this isn’t the case. Nearly every year the EU directives on sulphur reduction become tighter, helping to lower the amount of environmental pollution. If a problem can be fixed by adjusting the feed of oil to the appliance (possibly as simple as cleaning the oil filter on the tank) or making an adjustment to the flow rate inside the AGA then the oil should not be blamed. “Bad oil” cannot be changed to “good oil” by changing the flow rate, as it is the same oil.

It is important to note that the AGA brand of cooker is handmade and performance will therefore naturally have a slight fluctuation from model to model. The environment, your installation, its operation, and it’s maintenance will all affect the model’s delivery of heating and cooking times.

Nothing beats an Aga Roast

The Federation of Petroleum Supplier and Oftec produced an Appliance Combustion Issues Industry Briefing note back in 2009 which can be found here: Appliance Combustion Issues Briefing Note 2009