An explanation of some of the terms and phrases used on this site. Also take a look at our FAQs or try searching for what you’re looking for.


The mechanism used on certain wood chip boilers which stirs the chip to prevent it 'bridging'. Wood chips are not free flowing like pellets and needs an agitator to stir the fuel and help it to move smoothly through the boiler into the burning chamber.


Is a word derived from biological and mass. In the context of renewable energy it is simply anything that has been alive. Biomass boilers generally run on wood pellets, wood chip, cereals and logs. However there are many different boilers on the market, that may run on a combination of biomass fuel sources.

Biomass boiler

A Biomass boiler is relatively simple in principle, using wood or other biomass as the fuel instead of fossil fuels such as heating oil or gas. The biomass is augured or placed into the burning chamber where it burns to heat the heat exchangers. Hot water circulates through the heat exchangers into the heating system.

Buffer tank

Store the hot water that is distributed around the central heating system. The tank acts as an interface between the boiler and the heating system, so several heat sources can be incorporated, including solar thermal. Within the thermal store a heat exchanging coil can be fitted to provide mains pressure hot water.

Carbon neutral

Refers to the fact that the biomass absorbs the same amount of carbon while growing as it releases when burnt.


Commissioning involves safety checks, programming of the appliance and training on the operation of your biomass boiler.

District heating schemes

District heating schemes involve one boiler to heat multiple premises such as a block of flats or a row of houses.

Expansion vessel

The pressure vessel is linked to the central heating system and replaces the header tank traditionally.


A flue is a duct, pipe, or chimney for conveying exhaust gases from a biomass boiler to the outdoors. Biomass boilers require twin wall flue.

Fully automated

The Guntamatic range of boilers are fully automated and their settings managed by touch screen control panels.


Grain refers to oats, wheat and barley which can be used as an effective biomass fuel.

Heat mains

Heat refers to the use of underground pre insulated pipes to distribute heat in the form of hot water across distance to minimise heat loss.


The hopper on the boilers is either integrated with or positioned next to the boiler. It holds the biomass fuel for the boiler. Hoppers may have a feed mechanism at the bottom so the biomass material can be augured into the burning chamber.

Hot air machines

These are stoves or boilers that produce hot air that is blown into a room or space. They can be linked to ducting for more even heat distribution. Hot air machines can also be referred to as space heaters.


Miscanthus is a fast growing grass that can be pelleted and used as biomass fuel.

Pellet boiler

A biomass boiler that uses wood pellets as biomass fuel. 

Renewable energy

Is energy generated from a renewable source. These include biomass as well as solar, tidal and wind technologies.


The capacity to maintain a certain process or state indefinitely. In terms of biomass, trees can be replanted and resources replenished.


A fast growing tree that can be used to make wood pellets for biomass boilers.

Wood pellets

Wood pellets are made from compressed sawdust and need to be of ENPlus A1 or A2 quality.

Wood chips

G30 wood chips are suitable for use in our biomass boilers with an average wood chip size of 3mm and a maximum moisture content of 30%.

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