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Accumulation tanks

THERMAL STORAGE SYSTEMS:
how to save your money by wood combustion ?

Increasing prices of liquid energy sources, uncertainty of gas supply from Russia made wood heating very attractive for many households in Europe. Cost of wood is still very cheap, comparising to gas or oil we have almost 50-70 % savings in cost of heating. Unfortunately, low costs of wood heating have some conditions to fulfill by end use – we have to reach constant heating efficiency minimum 80 % . To get such value in long horizon of time we have to use thermal storage system as support for our wood boiler. Why is reasonable to use accumulation tanks to wood boilers?

1) full use of heating efficiency of boiler reduces fuel consumption and sweeping problems
Most of sold wood boilers , has nominal output around 25 kW. By 25 kW wood optimum output, the efficiency is 70-90 percent. In winter, an ordinary single-family house has an average output requirement of couple kW. When reduced to 4 kW, boilers without thermal storage tanks will act as a tar-boiler, with efficiency falling to under 30 percent. Keeping them going requires large amounts of firewood, generating a lot of extra work such as sweeping. The risk of chimney fires increases and the neighbors will almost certainly complain. Besides of all problems ,by 30-40% heating efficiency we use double quantity of wood and no doubts, that 25 kW boiler with accumulation tank consumes ca 14 cubic meter wood, without thermal storage support , almost 20 cubic meter.

2) accumulation tanks keep return water on high level, which protect against condense damages
Condense problem we meet in almost every boiler, where return water is to cold (under 45 C) and flew into hot are of heat exchanger. This water changes in steam which damages easily almost every wood fired boiler. We can say,there is a very high risk of corrosion in the boiler if the water from the tank is not pre-heated. Corrosion substantially reduces the service life of boilers, with some have to be replaced after as little as 3-5 years. Accumulation tank connected with special mixed valves integrated with pump like Laddomat, ensures that the boiler reaches its working temperature quickly. The cold water in the tank is pre-heated by the Laddomat before it reaches the boiler. It works like this, we have 2 heating circles : one boiler with accumulation tank , second installation and accumulation tank; valve is opening installation circulation when temperature in accumulation tank reaches minimum 60°C. With such protection system, we have always guarantee, that return water is warm and doesn’t create any condense in our boiler.
To optimise the benefits the tanks thermal storage capacity, it is important that the water in the tank separates into layers, during both charging and discharging.
Separation occurs when hot water is introduced slowly at the top of a well-insulated tank. Hot water is lighter than cold water, and it remains at the top of the tank without mixing with the cold water at the bottom.
The hot zone at the top of the tank is clearly separated from the cold water at the bottom.
The boundary layer is 50-100 mm high. All the water above this layer is at a constant temperature, e.g. 80°C. The water below may be at 30°C. The temperature of the water in the boundary layer ranges from 30°C to 80°C.

2) thermal storage systems make end user life more comfortable

I wrote , that by accumulation tank, we can save life of the boiler and cut fuel consumption. Another very important issue is comfort of boiler’s use. Becouse we are loading hot water to the accumulation tank, and wood fired boiler is working couple of hours with high capacity, later, when hot water is released to installation system, your boiler is not working. A good control unit allows the boiler to reach a full working temperature of around 80–90°C. Once this has been achieved, the boiler primarily heats the house, and any remaining hot water is stored in the thermal storage tank. The tank is normally fully charged after 3-4 hours firing . When accumulation tank is well isolated, we can have situation, that period whem we don’t need to fire wood boiler, could last about 12-18 hours and wood fired boiler doesn’t has to work ! So by good regulated thermal storage systems, we supply fuel in Your boilers once per day.

For those customers, who following arguments were so interesting, that they would like to buy thermal storage system important question could be also : How to select proper accumulation tank to Your installation system?

Norm EN 303-5 gives You special formula (approx. 10 litres per square metre of living space) By such selection, correctly connected thermal storage tank allows the boiler to achieve its maximum output of 25-50 kW, at a high temperature and with an efficiency of 70–90 percent throughout the firing period.

V= 15 TB * QN [ 1-0,3 (QH / Qmin ) ]

V – volume in liters of accumulation tank
TB - time of combustion in hours
QN - nominal capacity in kW
QH - heat load in kW
Qmin - minimal capacity in kW

Laddomat system

Laddomat^® 21

A charging unit for a solid fuel boiler to a storage tank with a hot water heater and a mixing valve for the heating system. Laddomat 21 enables the boiler to attain a working temperature of 80° C in a very short time. Charging is continued by means of a slow flow of hot water.

During the final part of the burn-out the Laddomat 21 charges the storage tank fully due to the unique thermal valve, which closes the bypass opening completely.
When the fire has gone out, Laddomat 21 makes use of the remaining heat in the boiler and ember by the self-circulation of hot water from the top of the boiler into the storage tank. Energy is stored in the tank instead of being lost through the chimney.

In the event of a power failure Laddomat 21 starts charging the container immediately by self-circulation. The same happens if the pump breaks down. Reverse circulation is prevented during periods of non-firing, which means almost no loss of heat.

The valves have extra large openings to cope with the maximum flow at the end of the charging period and during self-circulation.

Laddomat 21
Article No 11 23 78

Download further information about
Laddomat 21 as PDF-file

Article No	*Description*
11 23 78	Laddomat 21 with Wilopump RS25-6/3, 3 valves R32, 3 thermometers, thermostat 78° C, extra thermostat 72° C included.