FARM 2000

Choosing The Correct Batch Loaded Boiler

How much wood or straw will be required?

When burned in a FARM 2000 boiler, a typical small dry bale with 16% moisture content, weighing 16 kg (35 lb.), or a slightly lower weight of wood (approx. 14 kg), will provide roughly 40 kWh (136,000 Btu) of heat. This is approximately equivalent to the heat provided by 5 litres of oil. This gives a guide to working out straw or wood consumption in comparison to current oil usage. If there is no existing system to compare with, calculate the maximum heat load required and assume an average winter requirement of 60% max. heat load for 15 hours each day, to work out daily consumption.

Example:

50 kW (170,000 Btu/hr) maximum heat load

Average Daily Winter Heat requirement 50(kW) x 15(hrs) x 60% = 450 kWh

Average Daily Winter Fuel requirement 450 / 40(kWh) = 11 bales (or 160 kg wood)

The above is based on a thermostatically controlled heating system with night temperature turned down by 5°C or more.

Boiler Size?

Having calculated the heat load and daily fuel consumption, the boiler size can be selected.

The outputs quoted on the data sheets are based on stoking an average of twice per day through a heating season. Wood, straw and other waste type fuels have similar calorific values by weight but the boilers have a higher rating for wood because more weight (thus more energy) can be put into the boiler at each stoking.

Decide on the main fuel to be used before choosing the size of boiler, based on required stoking frequency. If there is access to both wood and straw then a smaller boiler can be selected (than if straw burning only) with the wood being used in the coldest periods of the winter and straw for less severe conditions.

For further details, see FARM 2000 Boiler Size Guidance.[pdf format]