Wood Fired 2 Oven Boiler Cooker Technical Summary

Wood Fired 2 Oven Boiler Cooker Technical Summary

Our innovative new design of wood fired boiler, using our patented Thornhill Turbo Technology (T3), combined with other innovations, makes this the cleanest burning boiler cooker in the world that does not require electricity or expensive catalysts.

However in keeping with ESSE & Rayburn, I have withdraw the boiler cooker from the market. Why?

Whilst it just about works the concept is really against the laws of Physics.

This is a difficult and tricky subject. There are many engineering and design problems designing a wood fired boiler and trying to make it a cooker as well makes the problems even worse.

It is difficult to get sufficient output from a cooker boiler using wood to heat a normal house, even then the amounts of wood burnt are huge, around 6-8 cubic meters a year. The problem is the water jacket, which is relatively cold at around 70C preferentially absorbs most of the energy from the fire.

This mean you must push the appliance hard to get the oven to 200C and the hot plate to 280C to cook.

Heat up times for the oven are then 2 hours + compared with 1/2hr for my 3 oven ‘dry’ cooker.

A better solution by far is a wood stove/boiler or a dedicated wood boiler, and a separate dry/non-boiler wood fired cooker in the kitchen. (more controllable and easier to cook on). Our dry cooker can be heated to oven 180C in ½ hr from cold, and stay at a steady 200C with just a 1-1.5kg log an hour, heating the kitchen and making an easy to use cooker.

It doesn’t matter that the outside of the wood stove in you sitting room is only 100-150C, there is plenty of heat fro the room, but try cooking in an oven at that temperature and you can see what it mean. You need hot plate temperatures of 300C and oven 200-200C, virtually impossible with a big water jacket at 70C, the heat just wants to flow into the water jacket.

It does work fairly well with coal if you keep the stove in for many hours, but should we really be burning coal domestically? It is the dirtiest most polluting fuel, even when burnt with high technology in a power station!!!

Please  consider a dry stove and a good dry stove in the sitting room. This will use a reasonable amount of wood per year, around 6 cubic meter for both, and provide most of your heating except Nov, Dec, Jan & Feb when you will need to use the central heating as back ground heat to supplement.

If you have huge amounts of free wood and the energy to cut and stack it, consider a separate dedicated wood boiler, or boiler stove. I recommend three which I have fitted and had happy customers with:

Charnwood Island III,                 Dunsley Yorkshire CH                Arada Ecoboiler Stove

Forget bout just a small water jacket to heat hot water, remember we don’t use much hot water these days. We use showers and dishwasher and washing machines are all cold fill. Think in terms of £60 a year on oil to heat water.

If you want to go the whole hog and have just wood and are currently on oil, look at you bill and find out the approximate oil usage in litres per annum. Multiply this figure by 0.0038 to get the cubic meters of neatly stacked, dry wood. ( e.g. 2,000 litres is 7.6 cubic meters). In this climate you need to stack logs for at least 2 years to dry so you would need 3 wood stores of this size to cycle.

I hope this gives you some figures & helps you with your decision making.

Please don’t hesitate to ask any further questions.

Regards Graham.

Eur.Ing. G Thornhill C.Eng.

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