Solid Fuel Boiler

Often when considering types of boilers, we are only informed of the types that run on fuels piped into the home, such as an oil, electricity or gas boiler.

But, there is another alternative in a boiler that runs on solid fuel.

The description of what is a solid fuel boiler varies from person to person – some describing it as a messy alternative to “clean” gas boiler, electricity and oil, and others claiming a solid fuel boiler provides a more aesthetically pleasing system that could provide cheaper energy bills as the costs of fuels rise.

A solid fuel boiler is not vastly different in structure to your average combination boiler, it uses the same types of radiators and pipework on the whole and also can be used in underfloor heating systems. There are two major differences to be aware of when considering a solid fuel boiler, which are:

The fire inside the boiler, providing the essential running heat, can close down, but it cannot halt inside the boiler system completely – in other words, it must be active, even marginally, at all times. Because of this, a solid fuel boiler must always be connected to a hot-water system or a radiator so that the surplus heat created can be used.

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The more advanced systems will have a method of storing this heat for later use, but many solid fuel boiler systems rely heavily on being able to constantly dissipate heat through hot water or radiators. A system with open-vents is highly recommended, also, to help remove heat from the main source in the boiler, to prevent over-heating.

The water temperature is controlled in a solid fuel boiler using internal thermostats built into the system, meaning that the temperature controls and gauges are often situated in the area of the heating circuit of the boiler.

What Is “Solid Fuel”?

The fuel a solid fuel boiler runs on is referred to as “solid fuel”, solid fuel can take many forms, such as coal, wood, paper – the safe fuel you would normally feed a fire with at home, although it is highly advised against feeding a solid fuel boiler with processed types of household rubbish that are often used in fires or bonfires, due to the increased risk of mess, blockages or even combustion.

Most solid fuel boilers are “fed” with solid fuel in a similar way as you would a fire, but there are also some solid fuel boilers available on the market that appear to run in the same manner as other types of non solid fuel boiler, with pellets of solid fuel being fed into the machine from a storage unit, or “hopper” situated outside of the house.

It has been argued that solid fuel systems are messy and inefficient due to their nature of being an open fire, and, being an open fire, they require a thorough cleaning out at least once a day to ensure it burns effectively.

Types of Solid Fuel Boiler

Because of the nature of solid fuel, there is a much more limited range of systems in which a solid fuel boiler can run with. These systems are often very aesthetically pleasing, with a rustic old-world feel and the often rare sight of a fire running in a modern household. The types of systems include:


Stoves with either free-standing boilers, or central heating boilers set into the wall of the household, which can often burn a large variety of solid fuels. These often come with a thermostat, but rarely can be fed automatically via the hopper and fuel pellet system.


Cookers are available in outputs of up to 20kW, and are often available with a thermostatic controlling system. They are often chosen for their rustic aesthetic as well as their heat production potential.

Independent Boilers

Boilers that run on solid fuel come in a good sized range, some hand-fired, some running on fuels such as wood pellets that are fed automatically to the boiler fire – often with the ability to burn for many days on a single filling.

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