Cosi specialise in linked wood burning and solar heating systems either supplied or installed in Kent. Please call to arrange a site survey or an appointment in the showroom with our heating engineer.

Wood is a renewable fuel, and just about encouraged by the government. Other countries in Europe do better, but here we have a reduced rate of 5% VAT on wood boilers, their installation, and the installation of solar panels. Will we cut down all the trees? No, especially not in Kent and Sussex where we have abundant coppice woods. These need to be cut down/cropped every 12-16 years or the ecosystem at the base of the forest, wood anemones, bluebells, violets, etc. die off.

A small house on wood heating alone would use about 7 tonnes a year, so at 70 tonnes per acre, about 1.5 acres per household is required. Outside the large conurbations of London etc. we could be carbon neutral with our heating (four fifths of our energy goes on heating, the remainder on electricity for lighting, controls etc.) There is approximately 20 million tonnes of renewable wood available per annum in the UK, and 55 million tonnes in France.

The problems that arise are;-

  • The secret of efficient wood burning is dry wood. This means you must store your wood properly and plan ahead. A proper wood store of about 10 cu/metres volume is essential, half of which should be handily near the point of use, and dry.
  • To burn wood properly you need a combustion chamber temperature of around 4-500°c. This is impossible to achieve if you just stick a saddle tank around the combustion chamber. Few stoves burn properly with water boilers; the ESSE & Broseley wood cookers and the Charnwood Island IIIb, Country 16b & ESSE 700b stoves are probably the best on the market.
  • The calorific value of wood is low so you have to keep feeding it to get the output, which is not easy if you leave early for work and arrive home late.
  • You need to do some work lugging and storing wood, couch potatoes and those who think their nails are more important than the planet, read no further! They say wood warms you three times – when you cut it down, when you cut it up and when you burn it.
  • If you stick solely to a wood fired system the house gets very cold when you go away on holiday, or if you are ill in the winter and can’t face the trip out to the wood shed.

THE SIMPLE SOLUTION IS A HYBRID / LINKED SYSTEM; – Does it work? Yes, customers are reporting fossil fuel bills of between £50-200 a year!

By using a combined system of …

  1. a log wood stove or wood cooker boiler, plus …
  2. an oil, gas or pellet boiler, all installed using a thermal store, these problems can be solved. To complete the set up and to really reduce your carbon foot print to its minimum …
  3. a set of solar thermal panels is added. With this system, all the heat sources feed a common heat storage cylinder and water and heating are used as required. If you do not light the wood boiler then the oil, gas or pellet boiler will automatically come on and compensate the system without you having to interfere. In simple terms, the more you light the wood boiler and the more the sun shines, the more money & carbon ( if you’re using oil or gas) you will save. With added solar panels on the roof, 75% reduction can easily be achieved for just a little thought and effort on your part. You also have the added advantage of fresh, mains pressure hot water, giving strong showers without a pump.

Below is a diagram of the layout for a three or four bedroom house. COSI can supply all the parts in kit form for you to install with a plumber, or provide a full installation service in the south east. Please phone for advice for larger properties.

Diagram of a system layout for combining wood, oil or gas and thermal solar panels, using a thermal store cylinder.

Hybrid system

 

We can sell the thermal stores and solar panels directly to you for you to install or to get a local plumber to install for you.

 We believe ECO should mean ECOnomical as well as environmentally friendly

Thermal Store for Solar Panels

Prices exc. VAT:

Size
1500 X 450
1500 X 500
1800 X 450
1800 X 500
1,950 X 450
1,950 X 500
Approx.   volume (Litres)
210
250
250
320
270
355
Basic direct   Thermal store
£850.00
£1,037.00
£900.00
£1,140.00
£995.00
£1,270.00
Extra   pair of direct connections
£8
£8
£8
£8
£8
£8
Combined   F & E tank (Combi / Fortic) (+ 270mm on height)
£75
£75
N/A
N/A
N/A
N/A
Solar   coil + solar stat pockets
£115
£115
£115
£115
£115
£115
70mm   insulation
£38
£38
£38
£38
£38
£38
100mm   insulation
£100
£100
£100
£100
£100
£100
Extra immersion   heater boss (each)
£12
£12
£12
£12
£12
£12
Immersion   heater (each)
£50
£50
£50
£50
£50
£50
T/stat   & pocket (each)
£45
£45
£45
£45
£45
£45
Silver metal   cased finish
£165
£165
£165
£165
   £165
£165
Carriage   charge
£70
£70
£70
£70
£70
£70
Total   (add up your options)
If   purchasing with a wood fired boiler add 5% VAT (x 1.5), other wise 20% VAT (x   1.2)

 

The basic direct Thermalstore includes a 12 metre finned domestic hot water coil, a thermostatic mixer valve, a 2 litre expansion vessel, a pressure reducing valve, a check valve, one immersion heater boss, 50mm sprayed foam insulation, a cold feed connection and a vent connection.

Carriage charges are for delivery to anywhere in England and Wales. Additional carriage charges may be applied to deliveries to Scotland, Northern Ireland or ROI (if in doubt, please supply a postcode for a custom carriage charge quote).

Combination F & E units also come complete with a drain connection, a drain valve, a float valve and a high temperature copper float.

Units with a solar coil come complete with solar thermostat pockets top and bottom for sensors. If you are planning to use solar as one of the heat inputs to the Thermalstore, it is advisable to have extra insulation if there is adequate space available.

You can have two immersion heaters to make use of cheaper over-night electricity (economy 7 tariff).

Basic price includes 6 direct connection, 2 off boiler flows, 2 off boiler returns, flow return central heating, extra connection are just £8.00 each if you wanted say 2 heating circuits.

A taller thinner store is always better than a short fat one as you get more stratification (temperature difference between top and bottom).

One flow from the boiler (for the pumped oil, gas or pellet boiler) and the return from the central heating have ‘sparge’ pipes internally to encourage stratification.

If connecting an oil, gas or pellet boiler, 2 T/stats & pockets are required. 1 to control the boiler and one as an overheat thermostat, to turn the central heating on if the wood boiler or solar has heated the store to 90C.

The thermal store concept has been around for many years now, and I have personally used one in my home for 15 years. The beauty of the system is in its simplicity, 2 or more boilers/heat sources connected together without the need for electronics, valves or human interference.

Some manufacturers advocate the use of cheaper plate heat exchangers. There are a number of problems with this;

  1. The passage ways on a plate heat exchanger are very small, in a hard water area a water softener must be used, plus a filter system, other wise this type regularly clog up and need replacing. (They are used in all gas combi boilers, hence the low cost and short life.)
  2. No electricity = No hot water as they require a pump and flow switch.
  3. Pumps and flow switches wear out and go wrong, meaning more maintenance, servicing and of course cost in the long run.

With the above problems and very little cost saving by the time you have bought the pumps and fittings, I cannot see any advantage in using a plate heat exchanger system. Our thermal stores have a 12 meter long 15mm diameter finned copper coil. The output depends on the house flow rate and the temperature inside the store but is easily 25-30 litre/min. More than enough for 2 showers and basins. If you need more hot water, have 3 bathrooms or more, you are better off with 2 cylinders, and to charge the second hot water cylinder indirectly from the thermal store. Either a pump fed, unvented or using conventional cold water tanks in the loft. If you have more than 2 bathrooms, link a simpler thermal store to an unvented cylinder.

please email to ask more questions sales@cosi.co.uk