I called the fire department last night ... wood boiler clogged!

[Surfeurseb]

Hello,

For those who are wondering about wood boilers, little account of my mishap.

Wood log boiler, installed in 2005, by a professional.
Quickly, the reality did not appear as rosy as expected: a lot of wood loading work, cleaning, frequent ash removal, sweeping once a month, autonomy of less than 1 hours in case of extreme cold, .... I had already exposed these points previously in another post here: https://www.econologie.com/forums/remplacement-chaudiere-fuel-par-chaudiere-bois-buche-t5169-30.html

Well it was supposed to happen: yesterday at 19pm, all my fire alarms sounded, except the one at the top where we were. Smoke visible on lower floor, boiler still one floor below. Quick exit from the house with the children, in "no no no panic" mode, and call in the wake of the firefighters.
No flames visible from the outside, but not possible to enter the basement because of the very dense smoke, and what good is it, everyone went out.

The firefighters arrive, the big game. They manage to penetrate the basement, up to the boiler.

Cause: obstruction of the evacuation duct, backflow into the house by the valve present to prevent "over-draft" when there is too much wind.
No fire in it. Phew. But were we on the verge of being?
Opening to the 4 winds of the whole house, extinction and emptying of the boiler.
"do not relight your boiler before having had your entire installation redone: duct too small, lack of tightness, etc."

Balls!

The boiler had been on for three weeks, dry wood well protected in shelters, up-to-date maintenance by the installer.

I will post other details "cold", it is the case to say it!

Seb

[Rabbit]

It is on that a wood boiler is work.

I have one, although for the moment I mainly use a
wood stove / boiler. I've been using it for over 15 years
this type of heating.
For me there are 2 or 3 problems.

The first is that you say in the other post that your boiler
idles. It’s already not good. Indeed, this implies that
your boiler is oversized. In addition you use wet wood
(I don't throw stones at you, I also use damp wood, even worse
I use softwood). These two factors cause cooling
important smoke, more smoke is charged with water.

The second problem is the draft reducer. Too cold smoke
mixed with cold air is fatal. Missing more than ham. You
have an almost perfect smoker in your chimney flue. The
consequences are the ones you know about fouling
catastrophic of the boiler as well as the duct.
The combustion station that you observed, must most certainly be
produce during an external cooling which makes you grow the
boiler which ignites the tar, increases the draft and the 2 put
together herald an inevitable fire.

For the third point, I share with you the advice given to me by the former
owner of the boiler I have: Do not cover the chimney and plan
evacuation of rainwater at the bottom of the chimney. I did what he told me and never had a problem with driving.

I clean my boiler every two weeks max. Chimney sweep
twice a year, once when the cold weather begins and
the next one in late spring.

It is true that when there is wind and the wood is dry, the stove / boiler
heats up thoroughly, and it makes a good 25 ° c in the house but hey
will not complain. Thanks to the air supply regulator, the water does not exceed
not 90 ° C. I reserved 10 ° c of security because I have a vase
d open expansion. The usual temperature of the circuit is 70 ° C.
My stove is 20 Kw. The boiler + -60 kw. It is why I
no longer use it, it will be used when the barn is finished.

As for the power of the boiler, it must correspond
to the maximum that all the radiators + boiler can evacuate. Which had
open windows if it is too hot.
You could solve part of the overpower of the boiler
by connecting it to a water reserve which will store the heat. It will allow
to average the temperature of the house and be able to operate
the boiler at its true power. I have no room for such an installation
I just do laundry when it overheats. My washing machine
Miele is regularly stuffed with water at 80 ° cal fall and spring.
It simplifies the sorting of the linen, the wools have disappeared from the laundry basket.

[Surfeurseb]

It is on that a wood boiler is work.

I have one, although for the moment I mainly use a
wood stove / boiler. I've been using it for over 15 years
this type of heating.
For me there are 2 or 3 problems.

The first is that you say in the other post that your boiler
idles. It’s already not good. Indeed, this implies that
your boiler is oversized.

The term "idle" is probably not the right one. There are still two modes on this type of boiler: full heating or off, with the fire smoldering but which is no longer supplied with air (thanks to reverse combustion).
In the event of extreme cold, the boiler operates almost continuously.

In addition you use wet wood

This year, my wood has never been so dry, thanks to a well-extended shelter.

The second problem is the draft reducer. Too cold smoke
mixed with cold air is fatal

Planned from the outset by the installer, I cannot judge its relevance. It is true that the consequence is a cooling of the conduit, therefore easier condensation, rather not well ...
but without this, in case of strong wind, as it often happens here (finistère tip), the overstretching could lead the heating circuit to overheating.

For the third point, I share with you the advice given to me by the former
owner of the boiler I have: Do not cover the chimney and plan
evacuation of rainwater at the bottom of the chimney. I did what he told me and never had a problem with driving.

This is how it is done in my case. Result bof. The rain that enters the duct also contributes to its cooling, of course.

As for the power of the boiler, it must correspond
to the maximum that all the radiators + boiler can evacuate. Which had
open windows if it is too hot.
You could solve part of the overpower of the boiler
by connecting it to a water reserve which will store the heat. It will allow
to average the temperature of the house and be able to operate
the boiler at its true power.

The boiler is 30kW, I have a 700l tank for accumulation, it is still a recent and consistent installation.

Note: the boiler is not "clogged", the exhaust duct, yes. It was 3 weeks, including a week of strong winds, and wet weather.

Thank you Rabbit for your directions, it also allows me to look in the right direction.

In the meantime, we have lost all confidence in reusing this boiler!

[Obamot]

Wholeheartedly with you. We understand that this is a very painful situation!

So no need to add more. How lucky you were!

[Did67]

The boiler is 30kW, I have a 700l tank for accumulation, it is still a recent and consistent installation.

Note: the boiler is not "clogged", the exhaust duct, yes. It was 3 weeks, including a week of strong winds, and wet weather.

1) Coherent installation, we could discuss it: the ideal, for a wood boiler (that we do not stop once the fire is gone), is that the heat energy released by the flare-up of a full hearth can be stored in the buffer.

The ideal is that you light up, and you let it burn at a fairly brisk pace without "suffocating" (no regulation by the draft) ...

Coherent installations are more like 1 l or more of buffers (so that you only have to do one ignition per day).

What would be nice is to find the capacity (volume) of the fireplace, to give us the essence of wood, and we could calculate ...

2) It seems to me all the same very curious that a duct (dimaeter 130?) Is blocked in 3 weeks ... even in the hypothesis of a bad behavior of the combustion ("closed draft") and a "cooled" duct ...

Do you confirm a pickup during the summer? Was the bistre clear or was there stratification year after year?

[Did67]

Heck, forgot:

It is indeed a blocked pipe, not a chimney fire!

If I understand correctly, you have smoke detectors and that's great!

The only danger was choking. Not the house fire. A chimney that no longer draws, the fire suffocates or almost ...

Spectacular, but not really a situation of imminent danger. Check your smoke detectors carefully. Are they networked? It is important for the night, when we sleep: that if the one in the boiler room goes off, it "rings" the one in the upper corridor. Everyone is awake. We go out in peace as you did ..

I would also recommend you a CO detector, because before being invaded by smoke, a bad draft can result in the emission of CO, which is a sneaky gas (odorless, but deadly, you can "go" without surrendering account for nothing!). Do an Internet search: many more deaths than we think and much more than the swimming pools we talk about so much!

And with these two reservations, I would not be more worried than that (after proper cleaning of the duct and verification of use).

Maybe also "investigate" if the sweeper does his job well, and really scratches and comes out of the bistre ... or if he passes his "hedgehog" (the good one, the one adapted to the duct ???) quickly and passes more time to cash the check and issue the certificate ??????? This is where I would start my questions.

[Did67]

On CO, this:

http://www.sante.gouv.fr/les-intoxicati ... rbone.html

or this :

http://www.sante.gouv.fr/les-intoxicati ... rbone.html

http://www.sante.gouv.fr/les-intoxicati ... rbone.html

[Surfeurseb]

Heck, forgot:

It is indeed a blocked pipe, not a chimney fire!

If I understand correctly, you have smoke detectors and that's great!

The only danger was choking. Not the house fire. A chimney that no longer draws, the fire suffocates or almost ...

Spectacular, but not really a situation of imminent danger. Check your smoke detectors carefully. Are they networked? It is important for the night, when we sleep: that if the one in the boiler room goes off, it "rings" the one in the upper corridor. Everyone is awake. We go out in peace as you did ..

I would also recommend you a CO detector, because before being invaded by smoke, a bad draft can result in the emission of CO, which is a sneaky gas (odorless, but deadly, you can "go" without surrendering account for nothing!). Do an Internet search: many more deaths than we think and much more than the swimming pools we talk about so much!

And with these two reservations, I would not be more worried than that (after proper cleaning of the duct and verification of use).

Maybe also "investigate" if the sweeper does his job well, and really scratches and comes out of the bistre ... or if he passes his "hedgehog" (the good one, the one adapted to the duct ???) quickly and passes more time to cash the check and issue the certificate ??????? This is where I would start my questions.

You are right, Didier: clogged pipe.
He adjusted a CO detector in the boiler room, which was triggered first, then the smoke detector, from the floor above.
The problem is, for the boiler to choke, it is absolutely necessary that there is perfect sealing of the circuit, which is very far from being the case, just by the presence of the draft regulator (automatic valve which s 'opens if there is too much draft in the wind, so as not to force combustion in the boiler.

So the risk of seeing the fire catch in the conduit was present, and once started, it would strengthen the draft, vicious circle on the way.

Otherwise, there is no speed regulator on the boiler: either it is full head, fan on for advanced combustion, or fan off, and there theoretically smothered fire, which smoldering while waiting for the next restart by the thermostat.

I begin to understand little by little what happened.
Basically: windy, soft and humid week: boiler frequently dormant. But by design, if the draft is forced by the wind, and the draft control valve does not cancel the vacuum, the lack of tightness of the boiler, at the level of the fan, leads the fire to restart, but to slow pace. Too slow to have a good smoke temperature. Combined with a duct well cooled by the rain, the wind partly sup, the deposit of bistre accelerates at full speed, until reaching the incident.
Result: duct fouled in three weeks.

I used to do it every month, having already noticed a fairly quick fouling. In addition to sweeping and regulatory maintenance by the heating engineers.

What bothers me the most, finally, is that even by respecting a recommended framework of use, one can arrive at a serious dysfunction. It clearly misses a monitoring of the fouling and the tightness of the circuit, therefore of draft, by sensor.
The biggest risk remains the fire in the pipe, devious because not necessarily detected, and which could lead to a general fire.

[chatelot16]

the easiest way would be to remove the draft regulator

when there is a fan, it means that the boiler lets out cold smoke therefore with a weak draft ... there is therefore a risk of too strong draft

and between the risk of loss of yield due to too strong a draw, and the risk of intoxicating everyone in the event of blockage, I would have quickly chosen

another interesting thing to do: put a pressure indicator in the smoke pipe at the outlet of the boiler: a start of blockage of the pipe will be clearly indicated by an increase in pressure

it would even be possible to put an automatic shutdown of the boiler as soon as this overpressure indicates a blocked chimney

[Did67]

The problem is, for the boiler to choke, it is absolutely necessary that there is perfect sealing of the circuit, which is very far from being the case, just by the presence of the draft regulator (automatic valve which s 'opens if there is too much draft in the wind, so as not to force combustion in the boiler.

So the risk of seeing the fire catch in the conduit was present, and once started, it would strengthen the draft, vicious circle on the way.

Otherwise, there is no speed regulator on the boiler: either it is full head, fan on for advanced combustion, or fan off, and there theoretically smothered fire, which smoldering while waiting for the next restart by the thermostat.

1) Theoretically, even if the smoke from a lit fire escapes through the regulator, in the absence of draft through the chimney (and unless your draft fan is acting), the fire should suffocate or at least " vegetate"...

2) A chimney fire is quite another thing: it is first of all an accumulation of bistre (carbon - wet coal!); generally by high heat, post-combustion, this charcoal dries up in its part directly at the exit of the boiler, ignites and the phenomenon is amplified and can slip ... 1st step: close everything to "suffocate" while waiting for the firefighters - too often I have seen people "open" ...

I'm not going to say that there was no risk. In my opinion it was limited. Less than in a boiler operating situation "normally but at fopnd!".

3) The solution, for a peaceful sleep: install a REAL buffer, so that you only havea unique outbreak, unregulated, per day, without "on / off"; clean combustion, no "sleep" phase ...

I suggest you take a look at the calculation I mentioned.

In short: it is the pad that heats the house for 24 hours minimum; when you are there and the buffer is low, you make a single outbreak all at once to raise it ...

This is a well-calibrated modern installation (in addition, the combustion of wood then becomes much more ecological because it is much less polluting!).