OKOFEN: Choose a PE20 or PE25?

[guizmo6767]

Hello,
I am studying the replacement of my fuel boiler (Buderus logana 105G + Ecomatic) of 25 years of age (approximately) by a beautiful Okofen + silo (feed by worm)

I keep in my installation the following elements:
- Radiators
- 3-way valve

I asked for several quotes and I find myself with the following problem:
Do I have to go on a PE20 or PE25?

My house is located in Lorraine, it is an old farm whose outbuildings have been transformed into residential houses and the old house into outbuildings (everything is connected).

I currently occupy 139M2 on 2 levels (ceiling height on average 2,40).
I have plans to renovate a more or less long term (7 to 10 years) part of the uninhabited area to enlarge:

- 35 to 56m2 on the ground floor (maximum)
- 100M2 upstairs (large maximum)

In terms of insulation, I will have double glazing everywhere (this year I am replacing non-existent windows on the outbuilding side).
The walls are of stone or red brick, more placo and polystère.
The ceilings are insulated (glass wool)
There are double doors between the inhabited part and the outbuildings.

According to my calculations I have a current need of around 17 kW.
The installers offer me either a PE20 or a PE25. The choice is complicated because the PE20 can be restrained (it is the same machine as the PE15), which is not the case with the PE25 (we start on another range of machine).

If I enlarge, it is possible that the PE20 is not sufficient. By cons while waiting to do the PE25 may be oversized (What about consumption and efficiency).

I am also considering the idea of ​​leaving on the PE20 and adding additional electric radiators on the 100M2 of floor (bedrooms and dressing rooms) if necessary.

For information, my annual fuel consumption is around 2500 liters (a little more this year) over 8 to 9 months and without hot water production (we sometimes give a heat up during the 'summer' period). 'It is cold or very humid). Basically 300litres / month on average.

Although I am afraid that your opinions are divergent, I welcome your comments, advice and feedback.
I can also provide more details if you wish. The goal for me is to make the right choice.

Thank you in advance.

[Did67]

Cornelian. And classic!

1) effectively: 20 kW = same machine as 15 and 12 kW; 25 kW = same machine as 32 kW ...

So you have to choose.

2) Without a precise assessment, it is difficult to decide "categorically". The maximum power needed should be calculated following a thermal study of the building. Impossible to answer categorically without a precise study ... There remains the snitch!

3) That said, 2 liters is what I consumed in Alsace before switching to pellets. And my Okofen 500 kW turns out to be too powerful. The heating engineer insisted on putting me a 15! [around 20 m², good insulation - the best in 200]. Maybe I'll put it at 95 kW ...

4) The choice will also depend on two things:

a) possibility of using an extra (insert, stove, even convector or "small oil"): indeed, the maximum power is only requested during the tens of days during which the colds reach the minimums, and again, not every year; the rest of the time, we are "automatically" below ... So if we can top up on those days ...

b) ditto if it is possible to "neutralize" during these very cold weather, a room or two (guest rooms, laundry room ...), or even if the occupants of the house agree to bring the rooms to 17 ° and add a duvet ... or to have only 18 ° and to keep sweaters ...

5) I didn't understand correctly: would you add around 130 to 150 m²? There, obviously, you double the surface, so the need ...

So if you see anticipate this, no other way than to oversize for now and add a buffer ... For example 300 l ... Otherwise, while waiting for the extension, you will have a boiler that will only start / stop ... Over 7 or 10 years, this is really not the best! Wear of certain parts (fireproof valve, igniter ...) and electrical consumption (ignition) ...

[guizmo6767]

Thanks Did67

The problem is indeed Cornelian.
My fear is of course to overconsume (the investment then might not be one).
I estimate my annual consumption at 5 or 6 tonnes of pellets.

suddenly, I think the right choice (in the absence of a specific thermal study) is to boost the insulation, to switch to a PE20 (which can be clamped if necessary because for the moment I only have 139m2). Thereafter, increase the heating circuit in the most used areas and put an additional heating if necessary in the additional areas (or bedrooms).

Regarding the Silo, I also have a small problem (of space) because of a beam and, unless I turn this beam (or switch to suction), I could not install a silo of more than 3 to 4 tonnes (flexiloplus 2210 * 1670 * 2150). My two installers seem to say that it is interesting to have a small silo and to fill it twice a year because it is easier to clean. Okofen recommends a silo adapted to its annual consumption (the price of pellets falling with the quantity ordered) -> who to believe?

In short, the project is progressing and the final choices will be difficult to shelter.