Use Wood Boiler

[duduf]

Hello,

I installed now 1.5 months ago a Zaegel Held CKV35 Log boiler, reverse combustion, with hydroaccumulation of 2000 l (heating only).

From what I can understand, the fan seems to be "all or nothing", its speed must be fixed (but not specified in the instructions).

By these very low temperatures, I heat the house and the balloon in two complete charges.

At certain set values ​​(hydro at 85 °, boiler temperature at 90 °, smoke temperature too high (250 ° C)), the boiler stops and holds the embers.

What is its optimal use.
1 - Should I charge the balloon and maintain this charge? In this hypothesis, the boiler would be regularly at one of its setpoint values, so the fan would stop and resume when the value became good again. The load of wood would light up and choke intermittently.
2 - Should I continue as I do now, namely I charge morning and noon, the boiler burns everything and accumulates a part (balloon almost loaded to the max). I stay on the hydroaccumulation from 16:00 p.m. and only turn on again around 22:00 p.m. to "spend the night".

I hope I have been clear in my explanations.

Thank you in advance for your advice.

[Ahmed]

Your question is perfectly clear and legitimate.
Legitimate because there actually appears to be a contradiction between the mode of operation of this type of boiler and the principle of hydro accumulation.

These 2 systems were developed to remedy, each in its own way, the problem posed by the fact of providing a large amount of fuel at one time, while wanting a quality combustion, distributed over time.

Hydro accumulation made it possible to provide a thermal flywheel to conventional log boilers, by smoothing out the significant variation in heat production specific to these rudimentary devices. This corresponds to your "2".

The reverse combustion and controlled draft boilers (all or nothing), theoretically allow them to modulate heat production by themselves. This corresponds + or - to your "1".

In practice, we note that some manufacturers juxtapose these 2 systems, perhaps to compensate for a certain insufficiency of this boiler solution?

From a theoretical point of view, this type of combustion (which I practiced) is not entirely satisfactory in several respects. From the point of view of the quality of combustion, even if this constitutes a big progress compared to the traditional boiler, the transition phases still produce a lot of unburned. On the other hand, the distillation of wood produces an abundance of acetic acid which quickly attacks the walls of the boiler if their temperature drops below the dew point (be careful in particular at the bottom of damp walls).

It is for this reason that I am convinced that wood chip boilers are more logical in operation, since we regulate fuel and oxidizer jointly (instead of playing only on the oxidant parameter). I readily admit at the same time that the prices of these devices are prohibitive…

Well, I did not answer your question, but I hope I have provided you with some information…