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Aspects to be taken into account

Martin, 37 years old, from Lincoln, UK, writes:

I live in an old house of about 100 square metres. In view of having to change the gas boiler soon, I would like to opt for an environmentally sustainable solution, for instance a pellet boiler. What aspects do I need to take into account? How can I calculate which one I need to purchase? Are any accessories required as well or is the boiler sufficient? 

Riscaldamento con caldaia a pellet e pannelli solari

The MCZ Group Customer Service replies:

Dear Martin,

In choosing a biomass heating system, it is necessary to assess various aspects: the heating requirement, available space, domestic hot water requirement.

First of all it is necessary to assess the building's heating requirements: in your case, an old 100m2 house in the Lincoln area, its thermal requirements (need for heat, to simplify) is different from that of a house with the same surface area but recently built, with proper insulation and located elsewhere. The degree of insulation of the door and window frames, insulation of the walls and the place where the house is are all elements that concur in defining the building's thermal requirement and consequently point to a product with a certain thermal power.

In this case, let's assume your house has a low level of insulation and, being in an area with mild climate, we might calculate a thermal requirement of approximately 10,500 Kcal, which is equivalent to about 12Kw. Therefore, only for heating you would need a product - stove or boiler - of at least 12 kW power. To manage domestic hot water as well, you should opt for a boiler with greater power, for instance a Compact 18 by RED.

Compact 18 is especially suitable for small rooms. Since it has a DHW unit (circulating pump and expansion vessel) already built into the structure, it is ready for use and may be connected directly to the system easily and quickly. It is available in the Easy Clean version also, an exclusive cleaning system of the brazier and the turbolators, that allows you to forget your boilers for several months. It is equipped with a handy trolley to make it easier to remove and move the ash, as well as an automatic turbulator and brazier cleaning system with a compressed-air system. 

Easy Clean per caldaia a pellet

Having adequate room available in the utilities room, it is always recommended to insert a thermal buffer tank, able to store the heat produced by the boiler and release it based on the system's demands, independently from boiler ignition times. Furthermore, with a buffer tank a high amount of domestic hot water is available instantaneously. In your case, a 500-litre puffer pipe in tank might be suitable, able to use the heat produced by the pellet boiler, assuring maximum system efficiency and always ready volume of domestic hot water.

Through the puffer, the system may be integrated to other heat sources, such as thermal solar panels. The combination of the biomass boiler with solar to manage heating and domestic hot water production is the most environmentally sustainable solution. Solar energy may contribute to the energy requirements for hot water production and also give a significant contribution to heating.

RED-branded solar heating panels have a wider buffer surface compared to traditional panels, which translates into a higher panel yield and a reduction in installation costs (the number of solar panels required to have the same heat production is lower than those required for installing a standard solar heating system and the number of connection points is lower).

The heating system may be controlled by a single electronic control unit which optimises the operation of the various heat generators, thus controlling heating comfort and integration of the various sources of heat.

Since there are several aspects to be assessed, as you might have understood, the first step to be done is to contact an engineer or specialised dealer, able to assess the various parameters and to create the most appropriate system for your specific case.


Best regards,

The MCZ Group Customer Service


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Dear Sir/Madam, just want to check something. I am looking at the red compact 24 and the specs say the pellet hopper holds 70kgs of pellets and this amount of pellets will give a burn time of about 16 hours. Do these units need to run constantly or are they turned on and off being thermally controlled thereby spreading the 16 hours out over a greater period. Because if they were to burn the 70kgs in 16 hours you would be looking at about $75 per day in wood pellets. This would therefore render this to be very uneconomical in deed. Please tell me that i have got it wrong and maybe advise me what an average daily pellet usage i could expect using a compact 24. I am new to the world of wood pellet heating.
Any other information you can provide would be great.
Kind regards,
Roger TAIG

Hi Roger, usually the technical sheets report two values for the runtime: the first value indicates the runtime at minimum power and the second one at max. The boiler will never runs the whole day at min or at max, but it will automatically adjust the power according to the heat demand. The calculation of the average daily pellet usage it is not simple, because it depends on many issues (volume to be heated, insulation of the house, daily routine...). You can ask to a retailer to make an estimation for you, based on your specific case.

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