Farnborough Hall ESCO Project

Farnborough Hall castle


Farnborough Hall is a grade 1 listed stone house in Warwickshire where we have installed a new wood chip boiler on an ESCO agreement.


Farnborough Hall had a collection of oil boilers , some dating back to 1976, with an oil consumption of around 23,000 litres per annum , with the air temperature still well below modern expectations, average 17 degrees.

Within the site there are four independent copper and one 1920's  iron heat circuits, all of which had their own boiler and control system.


After nearly one year taken assessing the situation and weighing up all the various options (including solar, heat source, wood pellet, etc) , it was agreed that Wood Chip was the way forward and so the planning and grant application stage started.

A further year later , after a bat survey was completed and both local authority and National Trust permissions where granted , we finally got to start the installation process.

Determined to minimise running costs over the expected 25 year lifetime of the boiler ( and hopefully a second 25 year boiler lifetime as well) , we designed a bespoke low cost underground chip store.  We proved that 'underground' does not necessarily mean 'unaffordable'  .

Using standard pre cast concrete silage pit walls, and an experienced and determined specialist contractor, we overcame several obstacles such as ground water , and now have a fully functional 60m3 underground store that one trained delivery driver can discharge into without the need for expensive and unreliable blowers or rehandling equipment.

To minimise the effects of  potential leaks and to provide complete control of each zone, it was decided to fit 4 heat exchangers and largely leave the old pipework system intact, other than taking the opportunity to update controls and replace pumps whilst specialist contractors were on site.

Kamstrup meters have been installed on the different circuits to be able to fairly apportion heat usage.

A Gilles HPA RA160KW boiler was chosen for its reliable reputation and suitability to the heat load of the various users.  The boiler was commissioned in summer 2010 and has completed to date 300Mwh heat ( see statistics below)


The first year had a few niggling teething problems , but probably no more than you would expect form any system that has been replaced on whatever fuel source.

The boiler has performed remarkably well, in fact as we had been led to believe  that it would .

The chip store design is something we will always remain proud of  as we have still not seen a chip store that in any way matches this one in terms of value and practicality. Further more it blends into the landscape well considering it is flanked by a grade 1 wall and a grade 2 listed outbuilding.

We have kept the boiler running continuously throughout the year and kept meticulous usage records in order to evaluate efficiency at different heat loads. Efficiency at low load being important as this would determine whether electricity or wood is best used in summer months for hot water .


Esco Provider : Practicality Brown Ltd  Tel :01753 652022

Contractor / Boiler Agent : Energy Innovation Ltd Tel: 01544 332225

Fuel Supplier : Fuel Chip Ltd Tel: 01753 657280

Fuel Specification: G50W35

First Year:

Metered Heat Usage : 270MWh

Wood Fuel usage : 440m3

Energy Value of Hard/Softwood Mix at 35%  : 0.80 MWh/M3

Average Primary Circuit & Boiler Efficiency over year : 75%

Approx. Winter Efficiency: 85%

Approx. Summer Efficiency: 70%

NB : Please note that these figures are taken from Meter Readings which are taking into account the heat loss of the primary circuit , which is over a 90 metre run to the heat load. This means that the boiler efficiency is probably around 90%.


Given the varying heat and hot water demands of this site, Wood Chip was certainly the best choice of fuel and also the cheapest fuel.

The installation has allowed complete control of the air temperature on all circuits, and reaction time on demand is excellent, certainly as quick as oil if not faster thanks to the 600 litres of buffer water ready to react on demand.

The Chip Store design has proved excellent and allowed deliveries even with 6" snow on the ground to be made safely and efficiently, once the local roads had been cleared!

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