To know which power of boiler with the pellets to choose

[vanou]

Hello

We just bought an old house where everything needs to be redone , anyway we want to install a pellet boiler but have no idea of ​​the power to take, knowing that we have a surface of 160m2 and that we want to use it for heating and water (family of 4)
I await your answers with great impatience
Thank you

[Philippe Schutt]

A boiler only used to recreate the calories lost by the house, you have to know what power your house emits with say 20 ° inside and -xx ° outside depending on where you live.
there are calculators on the net that do this depending on the composition of the walls, the thickness of the insulation etc ...

Already in the ladle, a non-insulated and single glazed house 0,2kw / m2, so 32kw ​​for a not very cozy nest, 0.1kw / m2 if double glazing and small insulation and 0,05kw / m2 so 8kw if super-insulated . We add a little something for the bath water and a small safety margin, that's 35kw, 20kw, 12kw, which you can reduce if you live in a warmer area than Alsace
Knowing that the budget can go from 5000 € to more than 20000 €, it's worth isolating first

[vanou]

Thank you for your answer.
we will of course insulate the house first with wood wool and the windows already have double glazing , we live in seine et marne.

Thank you again for your information Philippe

[dirk pitt]

indeed, as stated, it is always advisable to isolate.
Regarding the pellet boiler, I advise you to read the article that I wrote there 1 or 2 winters on this site HERE
what is very important is especially not to oversize a pellet boiler by saying to yourself: who can do more can do less.
most heating engineers still reason with fuel oil where it is easy and without adverse consequences on the output, a 30kW boiler where there is a need for only 15kW
with pellets, it's quite different because a wood fire (that's what it is) does not modulate as easily as an oil burner.
for the estimate, I can try to give you some first approximations but the ideal is a real heat balance.
information that would allow the data to be cross-checked would be to know approximately the average consumption of the former owners.
I also need the place (to know the DJUs in the region, the occupancy rate: absence during the day or not, 5 days out of 7 or other.
Is there already central heating by radiators? if so, what types of radiators, their number and ideally their power (or estimated according to their size)
is it a single storey house or a basement?
total volume heated? is it 2m50 under the ceiling? if or, that's about 160 * 2.5 = 400m3
where do you plan to store the pellets? if you have a large basement or a shed, I advise you to do the storage yourself: it's easy and it really lowers the price of the installation.
you must know that the storage place is not necessarily adjoining the boiler. one can use a pneumatic transport between the two but in this case, it is the reverse, it increases the price a little.
the other thing to check before starting is the availability and prices of pellets in your region. call the suppliers and ask for the price delivered to you for 3 or 4 tonnes.

[Macro]

When we made my radiators caluls (central heating) with the plumbers, he told me 60W of the m3 ... In my insulated roof spaces 260mm green wool crawling and 150mm rigid on rectifications ... For bedrooms (even the one which culminates in the cathedral at 5m50 meters from the ground) it is largely sufficient (for my climate in any case) often there is only one radiator out of the two open ... In the low rooms ... ( ceiling a 2.5) the heat coming from the ground floor (wood floor, brick ceiling and 10cm of glass wool in the middle) is sufficient to sleep ... Downstairs is another thing ... No insulation and cast iron radiators monstrous...

[dirk pitt]

.... and monstrous cast iron radiators ...

precisely, the monstrous cast iron radiators are very good.
in fact, to deliver a given power: that required for the room, the larger the radiator, the lower the temperature of the water that must be circulated therein.
However, the losses in the production of hot water (boiler + pipe) are lower the lower the water temperature.

It is therefore better to have large radiators with 45 ° water inside than small ones with 65 ° water

In terms of materials, cast iron has another advantage, it is its greater thermal inertia. there are therefore fewer hot-cold jerks, but now all the regulations (or almost) are proportional so it is less important than with a regulation which cuts off the circulator when the setpoint is reached.

[Philippe Schutt]

And if your fuel oil is still operational, you can just put a hydro pellet stove as a backup to the boiler. this is what will cost you the least and will save you the most money, while maintaining a certain degree of automation in the event of prolonged absence.

[vanou]

Thank you all for your advice