wood boiler and power failure

[foxmk]

Hello,
I ask myself a small question: how do you do when you heat yourself with a wood boiler that heats a hydraulic circuit on radiators (therefore with a circulator) and there is a power cut? In this case, the water no longer circulates, the boiler rises in pressure, empties its water ... but the fire continues to burn ...
Is this not dangerous for the house, the heating circuit, the boiler?
Are you emptying the boiler? And if you're not there, what's going on?
I hesitate to install a new wood boiler and again this evening, after a 2 hour power cut, I emptied my wood boiler so as not to risk overheating.

[Christophe]

There are (at least) 2 ways to avoid this:

a) Thermal safety valve (also called thermostatic safety valve) which opens and injects cold water into the boiler: it is compulsory for assembly (insurance) and often included with the boiler! Some explanations and plans here: https://www.econologie.com/forums/photos-et- ... t4368.html

Problem: when it injects, the overpressure of the network opens the valve of the safety group of the heating network and there is a risk of flooding (unless it is drained to the drain but it is rarely the case!) ...

b) Put an inverter on the circulator

Example: a very small 400VA inverter has a small 4.5Ah battery or 54 Wh capacity. A 45 W circulator can therefore run for more than an hour.

Obviously that only pushes the deadline but an hour is not bad ... The ideal will be to have a capacity

It would therefore be enough to wire an old small car battery to the 45 Ah inverter to have 10 hours of autonomy ... and the problem is solved!

[Rabbit]

Or simply a thermosiphon.
Even without electricity it heats up, finally hot water
circulates.

[Christophe]

It is true good remark but not necessarily compatible with the hydraulic installation (requires oversized pipes) so in recent or new houses: not too possible ...

On the other hand we can imagine putting the DHW buffer tank in thermosyphon effectively ...

[foxmk]

This means that even with a recent boiler, with reverse combustion, which therefore works with a fan, this does not prevent overheating?
Is it possible for a buffer tank to absorb the overflow of energy if its connection allows operation in thermo siphon?
But for this type of operation, shouldn't the buffer tank be high? (higher than the boiler)
Thank you for your answers

[Rabbit]

This means that even with a recent boiler, with reverse combustion, which therefore works with a fan, this does not prevent overheating?

You have to see what the ventilator is for.

Is it possible for a buffer tank to absorb the overflow of energy if its connection allows operation in thermo siphon?

Of course no worries, the thermosiphon is less effective
, for ducts of the same diameter as a circuit with circulator.
But the 2 systems can be used on the same circuit, must
just remove the anti return. [/ quote]

But for this type of operation, shouldn't the buffer tank be high? (higher than the boiler)
Thank you for your answers

It is indeed desirable, but in the event of a power failure, the objective is to dissipate the heat and heat the building.
leave this care to the radiators.

[foxmk]

The fan is used to create the air movement necessary for the combustion of wood.
In addition, in my house, it seems that the thermosyphon works very badly if not at all, even if the boiler is one floor below the radiators ... This is why I asked if a buffer tank could absorb all the water. energy that would no longer go into the heating circuit of the house.
And finally, at the end of the day, if I am absent and there is a power cut, the circuit overheats, the security starts and empties the water, and after what happens for the boiler who continues to burn wood? Is there a risk for the house, is the boiler out of order then?

[Cuicui]

it seems that the thermosiphon works very badly if not at all, even if the boiler is one floor below the radiators ...

A circuit works as a thermosiphon if the pipes have a sufficient slope everywhere and if there are no spring-loaded non-return valves which impede the free circulation of water.

All these aspects must be taken into account when designing the heating system, so as not to be stranded, or even in danger in the event of a power failure. You should eventually see how to modify an existing installation without much cost.

[Did67]

have a sufficient slope everywhere and if there are not spring-loaded non-return valves which impede the free circulation of water.
[Img]

If there is a circulator as the first said forumeur, and if it is stopped during a breakdown, we already have an obstacle, right ???

[Rabbit]

The stopped circulator does a little resistance but
does not prevent the thermosiphon.