Project: Ardgour Log Boiler
Technologies: Biomass Boiler/ Stoves
A Värmebaronen Vedolux 30 wood boiler with two 750 litre water storage (accumulator) tanks- one of which has an internal chamber to provide domestic hot water. The tanks are connected to a LK Armatur smart control unit which regulates the temperature of the water flowing through the radiators depending on the outdoor temperature.
How it works:
Wood burners work by gasification; wood is super heated in a low oxygen environment to create a gas (syngas). This burns at a far higher temperature than just burning wood so is more efficient at heating up the water storage tanks. One load of logs is enough to heat the 1500 litres of water to 80ºC.
An internal thermostat ‘calls’ for hot water to be circulated when the house falls below pre-set temperatures. This thermostat has five programmable time zones so the temperature of the household can be regulated to suit the needs of the house (ie warm in the morning from 7am to 9am, cooler during the day when the occupants are out and then warm again for their arrival home etc.). To ensure maximum efficiency a smart control regulates the temperature at which the water flows through the radiators (right). To do this it takes the outside temperature to determine the desired flow temperature (see graph below), then it mixes the hot water from the tank with cool mains water as it exits- thus if the tank was at 60ºC and was the desired temperature was 30ºC it would mix the necessary amount of cold water to the hot water meaning that less of the heated water needs to be drawn off and the tanks stay warmer for longer.
This large store of hot water means that the boiler does not need to be firing for hot water to be circulating, so the fire does not need to be continuously stoked but just lit when necessary. The tanks are surrounded by 90mm of insulation to keep in the generated heat as much as possible.
What was it replacing?
Two storage heaters, three panel heaters and an electric boiler.
Who installed it?
Ferguson Energy Engineering Ltd
£16,000-Including the boiler and accumulator tanks, six new radiators and internal plumbing and an external shed with electric points.
Grant/finance received/will receive (FiTs/RHI etc)
Renewable Heat Premium payment of £2000. The interest free loan from the Energy Saving Trust of £10,000 (paid back over 12 years- approx. £70 a month). The system will also be eligible for the Renewable Heat Incentive payments from October. At the current tariff rate of 12.2p/kWh for biomass boilers the household should earn £1130 per year for seven years (minus the £2000 PHPP payment)
Estimated payback time:
The household has gone from using 25-30kWh per day, plus coal for the open fire, to keep the house lukewarm to 6kWh per day for a toastie home. Estimated savings on the electric bill are expected to be around £730 per year and then around £300 in coal. So on this alone payback would be 13 ½ years. However with the RHI payments (£5910 over seven years) payback should be just under 8 years.
Any planning issues:
None, the boiler house was within permitted development
Inconvenience/disruption levels of installation:
The owners took it upon themselves to build the boiler house (and associated wood store) but all the plumbing and electric work was done through the contractor. Taking the old storage heaters out and installing the new radiators took a couple of days (the house is a bungalow so piping was placed in the internal walls up into the loft). Installing the boiler and testing the system took around one week- but majority of this work was done outside so caused no disruption to the owners.
The fan for the boiler is noticeable when outside but it is only on for 4 hours or so per burn. The gasification style of burning actually means that there is less smoke than from the old open fire and all the smells and mess (from the logs and ash) are now outside rather than in the living room.
Onward running costs/needs:
The boiler requires occasional cleaning but special brushes were provided for the owners to do this themselves. No annual maintenance is required so the only real expense is providing wood to fuel it.
The owners are incredibly pleased with their boiler and find it very easy to use and very efficient. The house is warm on demand and the temperature can be increased at the touch of a button. As the house is reasonably small (two-bedroomed) the owners only need to light one fire a day in winter to have all their heating and hot water needs (approx. 0.14m3 of wood). In summer they only put on one burn every 4 to 5 days for hot water. Life has been made easier as the house is tidier (due to not having to drag wood and coal through the living room) and that they can go away and come home to a warm house.
If you did it again would you do anything differently?
Recommend the technology:
If you would like to speak with the owner about her project, please email Kendra Turnbull- firstname.lastname@example.org