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Wood pellet biomass boilers for domestic use

Hattie Hartman compares commercially available wood pellet biomass boilers for domestic use

In Austria, 80 per cent of new homes are equipped with wood pellet boilers as standard and bags of wood pellets are available from local shops. In the UK, rural homeowners are increasingly opting for wood pellet boilers as fuel prices escalate.

A typical house requires a 25kW boiler and a 6-tonne, 3m x 3m store. Some Austrian models have fully automated feed systems with integral hoppers, so that a ‘fit and forget’ approach is possible. Manual models are also available.

A big advantage of pellet systems over wood chip or logs is that the location of the store and the feed pipe can be flexible. Pellet feed pipes can even go around corners or under walls to fit into tight spaces.

But pellet boilers are expensive, costing up to £15,000 for a 25kW automatic feed model. Pellet quality and availability is also an issue, although sourcing has been made easier through the National Energy Foundation website.

www.bigbarn.co.uk/ logpile/indexen.php

Green-tec

Manufacturer Ashwell
Output 15kW
Dimensions 950 x 1,264 x 470mm
Efficiency average 92 per cent
Fuel 6-8mm wood pellets
Integral hopper Yes
Hopper size 120kg
Automatic feeding option Yes
Ash removal Weekly
Maintenance Weekly, by user
Warranty One year parts and labour, three years heat exchanger
Made in UK
Distributor Ashwell Engineering Services Limited et al

Ashwell is one of the few UK suppliers of wood-chip boilers. The domestic wood-pellet boilers range in output from 15 to 50kW. ZEDfactory promotes the 15kW model as part of its own product range. It can be turned down to 4kW output when demand is low.

Multiheat 2.5

Manufacturer Baxi
Output 25kW
Dimensions 1,578 x 600 x 1,475mm
Efficiency Approx 90 per cent
Fuel Wood pellets
Integral hopper Yes
Hopper size 360 litres
Automatic feeding option Yes
Ash removal Monthly
Maintenance Internal cleaning of heating pipes quarterly
Made in Turkey
Warranty One year parts/labour
UK distributor Numerous merchants, including Wolseley

Baxi boilers have been selected by Wolseley for promotion through their Sustainable Building Center.  The output can be regulated down to 30 per cent and as low as 1kW. Hopper can be filled from the top or from either side of the unit.

USP Easyfire

Manufacturer KWB
Output 30kW
Dimensions Vary depending on pellet-handling option
Efficiency 90 per cent plus
Fuel Wood pellets
Integral hopper Optional
Hopper size Varies
Automatic feeding option yes
Ash removal At least quarterly
Maintenance Chimney to be swept and boiler given visual check at least quarterly
Made in Austria
Warranty One year
UK distributor Econergy

Output ranges from 10 to 30kW. Numerous handling systems for feeding the hopper are available, including a suction system and a fabric silo. Ash compressor prolongs emptying intervals. The boiler is regulated by a microprocessor with a remote control option.

Pellematic PE20

Manufacturer ÖkoFEN
Output 3-20kW
Dimensions 1,130 x 899 x 1,090mm
Efficiency 91-93 per cent
Fuel 6mm wood pellet
Integral hopper Only available for the suction system
Hopper size 450-12,000kg
Automatic feeding option Auger or suction
Ash removal Three times a year
Maintenance Once a year
Warranty Two and five years
Made in Austria
UK distributor Organic Energy

Pellematic boilers are self-cleaning and can accommodate heating loads as low as 2.5kW. The front cover is available in green, red, yellow or blue. ÖkoFEN offers an optional prefabricated timber shed, the Ecobox, which can house the pellet boiler outside.

Readers' comments (2)

  • I've recently spent the relatively small amount of £4k on a fully automated 20kW pellet boiler. It's not commissioned and up and running yet but once it is rest assured I'll be adding updates on my blog of my eco house renovation http://greeninghillside.blogspot.com/

    Hopefully this will show that domestic biomass doesn't have to be ridiculously expensive.

    Unsuitable or offensive?

  • Will Frost

    Pellet boilers are suited for smaller domestic installations but once you get to 100kW and above it is worth considering wood chip systems. The fuel can be sourced locally and at a more economic price enabling a quicker payback on the boiler. Wood chip can also be blown into difficult to access overground fuel stores. We have helped a developer in Somerset design a wood chip store like this for a new block of flats.

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