Choice of granulated boiler power

[commandeur_brin]

Hello everybody

I just bought the house of my dreams in the Orne (61) and it is currently heated by good old bread rolls of families ...

After much thought I made the decision to install a pellet boiler with a network of radiator a priori cast and production ECS. I hesitated and compared the brands and I think to favor Okofen over Fröling and Hargassner.

The problem is the power of course. From everything I've read here and there, installers tend to overestimate the power or to call on a calculation of oil boiler. Blows I would like your opinion.

My house is a 17th century farmhouse which is 120 / 130m2 which include 30m2 of attic. A restoration was made in the 90 years almost all windows are double glazed. I will change the remaining 3. There are 70m2 attics to develop and I would like to size the boiler according to that recess.

My calculation is done on this basis: https://www.mychauffage.com/contents/ch ... -puissance

From the shots I made the following calculation:

Insulation Coef: 1,4
Volume: 200m2 x 3m high ceiling = 600m3
Temperature: 29 (20 + 9) The house is in a wood so I imagine cooler than in the open countryside
Power: 1,4x600x29 = 24360w
With a margin of 20%: 24360x1,2 = 29232w

If I believe what I hear on the right, you have to add almost 10kw for the ECS (I take long hot showers ...)

Blows I get to 40kw and it seems huge compared to a lot of posts read here and on the forum Futura-sciences.

What do you think ?

Another question, the transition to condensation is it a real plus? Is there no more risk of malfunction (More moving parts and piping)? I have the impression that the gain of the minimal ...

Thank you in advance for your help and feedback!

[dede2002]

Hello,

Others here can tell you better than me, because I have no experience with pellet boilers. But I think like you that 40kW seems exaggerated.

To compare, at home I have about 1000 m3 heated in a house of 19ème (4 apartments and about fifteen inhabitants) with a fuel oil boiler of 35 kW, changing jet to decrease NOx I brought the power to 20kW and that's fine.
The max power is calculated to ensure 19 ° or 20 ° during periods of great cold, to see the minimums in your area, but it is increasingly rare and can easily support a few days (once every 10 years ...?) with a lower temperature in the house.

For ecs, 10kW it heats about 300 liters in half an hour, it does not change much for the heating of the house (at home, about 20% of the total, with 15 inhabitants).

Do you know the winter electricity consumption of the former occupants?
Is the roof isolated?

[sicetaitsimple]

If I believe what I hear on the right, you have to add almost 10kw for the ECS (I take long hot showers ...)

Hello,
I neither have any practical experience with the pellet boiler. On the other hand, I do not understand this "10kW" more for the ECS?
When you heat the ECS, it actually decreases the power available for heating, but it is very temporary, you do not take anyway showers for 2 hours? At worst, the days when it is very cold, you will take showers a little less long!

There are real specialists on this forum, maybe they will appear. But I chose, to be interested but without following up, that they all recommended not to oversize a pellet boiler.

[commandeur_brin]

Thanks for these informations !

@dede2002 no past consumption, the house served as occasional cottage so electricity cut off half of the year. The attic was surely isolated in the 90 years during the installation of velux. I will sound when I finally have the keys! The roofs remaining to be developed are not isolated at the moment and I think quickly to do it even if I think there was an isolation between the DRC and 1er.

@sicetaitsimple I read it everywhere. But it's true that it makes sense and I tell myself that the possible additional power is a function of the buffer tank no?

I understand that unlike oil and gas boilers that operate in a short period of intense heating, pellet boilers work less hard but continuous. Blows if I take a long shower, my wife takes a bath at the same time and empty a ball of 300L, how long will the boiler not heat?

Thank you for your help to both of you!

[sicetaitsimple]

Blows if I take a long shower, my wife takes a bath at the same time .....

A suggestion would be to take a long shower or bath together, normally it warms up!

Truce jokes, it is obvious that if you do not control the instant consumption of ECS (for example as you quote in a house with cottages where you are not going to tell your visitors the shower is 10h00 to 10h15 ), it can possibly pose a small problem.
But I don't think so in a general case. Again I am no pellet specialist, but a boiler normally has a small buffer tank (not 300l, usually less than 100) but is normally able to instantly heat a "reasonable" water consumption.

[commandeur_brin]

I actually look at the Pellmatic Maxi Condens 25kw who has a ball of 100L.

There is very little price difference between the 32kw and the 25kw so I wonder if it would be better to take the 32kw and the brider to 25kw. I have the impression that it is anyway the case of the model 25kw ...

Like that, if it's not enough I unbridle and if enough I leave until the development of the attic! What about the addition of condensation? We win 10% theoretical efficiency but in fact I imagine that there are so many factors that there is not 10% savings on the monthly bill?

Edit: "100L balloon" and not "25kw balloon"

[sicetaitsimple]

Like that, if it's not enough I unbridle and if enough I leave until the development of the attic!

It also depends on the use you intend to make these 70m2 additional attics. If it is not a permanent occupation, but for example a temporary home for children in WE or a vacation or even as above a cottage, an electric solution is looked at, unless electricity as a heating mode gives you buttons .
But it's really much cheaper in investment than pulling pipes and conventional radiators, much more flexible in use.
This is what I did to build a large (high) attic above a ground floor of about 50m2 three rooms (a main room, 2 small rooms and a bathroom) not intended to a permanent occupation, and my faith I do not regret it.

[commandeur_brin]

It also depends on the use you intend to make these 70m2 additional attics.

When I have the means I will go up the two rooms downstairs. I do not like the full foot at all. Blows it will be for permanent sleeping and it's true that the electric gives me buttons ...

[sicetaitsimple]

It also depends on the use you intend to make these 70m2 additional attics.

When I have the means I will go up the two rooms downstairs. I do not like the full foot at all. Blows it will be for permanent sleeping and it's true that the electric gives me buttons ...

No problem, it was just a suggestion just in case!

[commandeur_brin]

It also depends on the use you intend to make these 70m2 additional attics.

When I have the means I will go up the two rooms downstairs. I do not like the full foot at all. Blows it will be for permanent sleeping and it's true that the electric gives me buttons ...

No problem, it was just a suggestion just in case!

A very good suggestion! I ask myself for example the question of keeping the electric heating of the only room on the floor while waiting to make savings of installation ...

We will move in the next weeks so we will largely be able to discover the effectiveness of the grids bread before work for the boiler in January ...