Darionti Ltd. T/A WoodHeat
The Old Creamery - Connonagh - Leap - Co. Cork
Tel/Fax: +353 (0)28 34411
email:

How our systems work

GENERAL INFORMATION ON HOW OUR BOILERS OPERATE WITH THE HEATING SYSTEM.

Ecotec, the pioneers in underfed combustion of efficient wood pellet burners since 1992, have tens of thousands of burners operating-up to 300kW in thermal buffered boilers.

All our systems have a buffer as part of the system and operate differently than, for example, oil boilers. Our boilers are always powered, even when not operating (for safety monitoring). They deliver heat into a store (either the boiler itself or an auxiliary buffer) and maintain this store temperature as a thermal mass of potential heat ready to be utilized by the heating and hot water zones of the house when they call for heat. When they do call for heat the circulation pump(s) are activated and the stored heat is delivered into these zones. As the store temperature drops from the cooler return water entering the boiler/buffer, the burner is then fired to replace the heat that is lost. The present need of energy is lower due to the fact that there is a hot start and the system is somewhat warm overall at the beginning of a heating cycle.

Boilers installed without the solar, have internal stores of 205 litres for the 20kW and 25kW boilers and 350 litres for the 30kW and 40kW boilers.

The Mini Q boiler, which is installed with a solar Buffer, has an internal store of only 55 litres, as it uses the buffer of the solar tank (which is boiler water) - sizes from 500 to 1500 litres.

The buffer serves three purposes, one aforementioned on the hot start for heating, the second allows for a longer period of burner operation which decreases burner cycling and the potential for seasonal inefficiency, and the third for the thermal mass of water to absorb the latent heat from the burner when the burner stops firing (max temp is reached).

When we install a system, the boiler is tuned to a very efficient setting whereby emissions, (O2, CO2, CO2 and efficiency-Lambda) are set. This setting is usually at the higher end of output range of the burner and the boiler operates to this setting when running.

A modulating boiler will change its setting to a lower kW output to match the small load on the heating demand. In many cases there is no buffer with this type of system. But, the fact that a boiler changes its output to a lower one means that there will be a temporary spike in emissions, and consequential loss of efficiency(like changing gears in a car) and when the lowest setting is used, there is a constant increased level of CO-usually twice that of the higher kW setting.

Customers can use whatever form of heat distribution systems that suits their needs-whether radiators, under floor heating or a combination of both. If using as buffer tank that is also heated by solar energy, the stored water should be allowed to be very hot; in this case we install a thermal mixing valve or bypass to keep this temp to about 65 deg C. before it goes to the distribution manifolds in the house. Likewise, thermal mixing valves are essential for domestic hot water as is a blending valve for the return boiler water in systems in boilers without the solar tank.

The boiler system is warranted for 5 years from the manufacturer as per standards for Sweden and Scandinavia. The life cycle is 20-25 plus years for our systems from experience in the field. On the burners alone, the first ones from the early 1990s are still operating well and, if required, are easily repaired for long-term value.

The boiler has a wood pellet burner attached or built-in. They are designed to work together as one unit. The Bioline Burners from Ecotec are in widespread use in Sweden, are very simple in design, reliable and easy to repair. (See Bioline Burners.) They operate on the basis of precision underfeed of wood pellet fuel into a burning chamber that is self cleaning of the ash residue. The wood pellets have consistent heat value per unit of measure and can be managed much the same as oil in an automatic way. The burning of solid fuel is far different than oil or gas in that the supply cannot be suddenly extinguished, and also the combustion chamber must be larger to accommodate the higher flow gas volumes. The higher flue gas temperatures must also be managed by the design of the boiler.

For safety, the boilers must manage the interruption of the fuel supply from the silo to the boiler/burner automatically. Whilst in some boilers this is accomplished by a single free-fall of pellets into the store of the boiler, in the Bioline burners from Ecotec, there is also a break in the store itself which always remains free from pellets in the event of a back burn. In addition to these two passive safety features, there are two mechanical sensors also which detect back pressure in the flue and also back heat in the feeding tube. In the last two cases, the boiler will shut down automatically.
For these reasons, and also because our internal store holds only a half to one kilo of pellets, we consider the Bioline burners to be the safest on the market. (See Safety.)




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