Chimney smoke sinking after it leaves flue and re-enters cabin

[nb Innisfree]

1 hour ago, Slim said:

When I said 'new issue' I meant for the OP

Ah, sorry, my mistook. 

[sueb]

I do hope you have a carbon monoxide alarm monitoring the levels

[jetzi]

2 minutes ago, sueb said:

I do hope you have a carbon monoxide alarm monitoring the levels

I have three. But even though the CO levels were OK the smoke bothered me a lot, feels like I smoked a pack of fags and I don't smoke.

 

(For the record the smoke isn't coming in all the time, and isn't right now, so it's at least somewhat dependent on the wind...)

[Richard T]

My money is on the flue being partly blocked where it meets the baffle plate. I suggest the OP lets the stove out and removes the baffle and then checks that the flue is not partially blocked. After burning some dodgy fuel ours blocked at this point.

[blackrose]

Could be a blocked flue/baffle plate but in these high pressure windless weather conditions you can get an inversion which keeps smoke from chimneys close to the ground. If there are other boats around you it could be their fumes you're smelling as well as your own.

[Iain_S]

The smoke failing to rise can be due to weather conditions; usually still air and a temperature inversion (warm air above cold air) near the ground. More common in winter, when the ground can get a lot colder than the air above it. The smoke emerges from the chimney, and begins to cool. If it cools to the ambient air temperature, it stops rising and spreads out below the warmer air above it. The smoke from a bonfire or camp fire can be quite spectacular as it spreads at low level from the source ... 

[jetzi]

On 06/01/2021 at 22:06, Richard T said:

My money is on the flue being partly blocked where it meets the baffle plate. I suggest the OP lets the stove out and removes the baffle and then checks that the flue is not partially blocked. After burning some dodgy fuel ours blocked at this point.

 

On 06/01/2021 at 22:45, blackrose said:

Could be a blocked flue/baffle plate

 

As today was a bit warmer I let the stove out and gave the flue a good sweep. Here are "before" photos of the flue (from top) and baffle plate. It didn't seem at all blocked to me, maybe 1mm of soot deposited all around. Would a blocked flue cause the descending smoke, anyway?

 

 

 

 

 

On 07/01/2021 at 00:06, Iain_S said:

The smoke failing to rise can be due to weather conditions; usually still air and a temperature inversion (warm air above cold air) near the ground. More common in winter, when the ground can get a lot colder than the air above it. The smoke emerges from the chimney, and begins to cool. If it cools to the ambient air temperature, it stops rising and spreads out below the warmer air above it. The smoke from a bonfire or camp fire can be quite spectacular as it spreads at low level from the source ... 

It hasn't happened again since I posted so I think it's just the weather conditions as you describe. I'm probably just expecting too much from stone age technology!

 

 

 

  

On 06/01/2021 at 10:17, system 4-50 said:

its not the stove that is the problem, its the other means of air exiting and entering your boat.  If the vents are such that the wind before your chimney finds it easier to enter the boat than leave it then your boat will be slightly pressurised and the vents behind the chimney will be exit not entry vents and will not take in smoke.  You need more entry-favouring vents on the upwind end/side of your boat.  

  

On 06/01/2021 at 15:53, Detling said:

have you got low level vents and are they blocked?  the air and smoke going up the flue has to come from the cabin and will reduce the air pressure in the cabin thus drawing in more air via the vents.

 

I think this is the best advice. If enough of the gas going up the chimney is being replaced by air coming into vents far from the exhaust, then there shouldn't be any suction drawing smoke in.

 

I think I might try to create more low-level vents. In combination with a longer chimney (which I haven't been able to find due to lockdown) hopefully this will sort it.
 

Thanks to everyone for the advice!

[Jen-in-Wellies]

41 minutes ago, jetzi said:

I'm probably just expecting too much from stone age technology!

Fire! Cave man television. ?

[jetzi]

Ugh, weather conditions are such that the smoke is sinking. I'm smelling smoke again and I'm feeling it in my throat. There's no wind so turning the boat won't help. I'm at my wits end here.

 

Having to make a difficult choice between suffocation or freezing.

Cleaning didn't help. I created more low level ventilation which hasn't helped. Opening the top vent on the Morso doesn't seem to make any difference. Haven't been able to get a longer chimney yet thanks to lockdown, but that's my last hope...

 

I'm using Excel smokeless fuel but I wonder if I should try a different brand?

[John Hartley]

I find the weather can have an effect both on the smoke and the ability of the stove to burn well pressure being the culprit. On foggy days the smoke has difficulty rising due to the higher external air pressure.

Stay safe everyone

[jetzi]

7 minutes ago, John Hartley said:

I find the weather can have an effect both on the smoke and the ability of the stove to burn well pressure being the culprit. On foggy days the smoke has difficulty rising due to the higher external air pressure.

I'm finding the stove is burning very well, it's just that the smoke sinks immediately upon leaving the chimney and sits around the boat at roof height. So all I can think of doing is raising the chimney, so at least by the time the smoke sinks it will be diluted by more air...

I think there was definitely a problem with having too little low level ventilation, causing the smoke to be sucked in the roof vents. But even if I leave the bow door totally open smoke still gets in so that can't be the whole problem.

 

It's really making me feel unwell so I have to kill the fire and put on a few more layers...

[Sea Dog]

20 minutes ago, jetzi said:

I'm using Excel smokeless fuel but I wonder if I should try a different brand?

I burned Excel as my fuel of choice for years and never had such an issue. Its either the your stove flue set up or the way you use the vents, but you had had the stove for long enough and you say the problem is a new one. With new problem, question No1 is "What's changed"? Something has, or you wouldn't be getting dramatically different results.

 

You don't sound confident in the use of top and bottom vents, but you say if you run the stove hotter it smokes more, which defies the laws of physics - a stove thermometer would show whether you were running hot enough or not, so get one if you don't have one. I'd suggest you also consult your Morso manual and other sources to read up on air controls in solid fuel stoves, just so you can stop doubting yourself there and have confidence you're not causing the issue. 

 

The only other thing that concerns me is the difference opening your doors makes. Are you sure there's not been a reduction in vent so the fire is being starved of air?

 

Since you've had the stove a while, it's unlikely that you're experiencing weather conditions which you've not faced before either, plus you're having this problem for too long for freak atmospherics to be the cause, so that now seems unlikely cause too.

 

Back to basics: what's changed since you and the Squirrel were getting along fine?

 

And don't forget that stove thermometer.

[Tracy D'arth]

You could always move off till spring into a flat with electric heating?

[Jen-in-Wellies]

2 hours ago, jetzi said:

Ugh, weather conditions are such that the smoke is sinking. I'm smelling smoke again and I'm feeling it in my throat. There's no wind so turning the boat won't help. I'm at my wits end here.

 

Having to make a difficult choice between suffocation or freezing.

Cleaning didn't help. I created more low level ventilation which hasn't helped. Opening the top vent on the Morso doesn't seem to make any difference. Haven't been able to get a longer chimney yet thanks to lockdown, but that's my last hope...

 

I'm using Excel smokeless fuel but I wonder if I should try a different brand?

What is the horizontal distance between the flue and the nearest roof vent? Any chance you could post a photo of the stove and flue pipe inside the boat and the roof in the area of the chimney outside? May give us some clues that can help.

 

Edited January 15, 2021 by Jen-in-Wellies

[Tony Brooks]

2 hours ago, jetzi said:

Ugh, weather conditions are such that the smoke is sinking. I'm smelling smoke again and I'm feeling it in my throat. There's no wind so turning the boat won't help. I'm at my wits end here.

 

Having to make a difficult choice between suffocation or freezing.

Cleaning didn't help. I created more low level ventilation which hasn't helped. Opening the top vent on the Morso doesn't seem to make any difference. Haven't been able to get a longer chimney yet thanks to lockdown, but that's my last hope...

 

I'm using Excel smokeless fuel but I wonder if I should try a different brand?

Excel really stinks, i think its the petro-coke it contains. Red from the same maker smells far less pungent but is not certificated for smokeless zones but it does not smoke much once going. I could smell the Excel on my stove all over the garden and down the road and that is from a  house chimney. Certainly try another brand.

 

 

[sueb]

What is the CO monitor reading?

[jetzi]

@Sea Dog I'm reading from your answer that the problem could be that the stove is too cool - which is highly possible...

  

2 hours ago, Sea Dog said:

if you run the stove hotter it smokes more, which defies the laws of physics

Perhaps I need to give it more of a chance. Opening the vents initially generated more smoke, after two or three minutes I closed them again.

 

2 hours ago, Sea Dog said:

a stove thermometer would show whether you were running hot enough or not, so get one if you don't have one. I'd suggest you also consult your Morso manual and other sources to read up on air controls in solid fuel stoves

I don't have a manual, didn't realise there was any complexity to operating a stove - basically all I do is open the bottom vent more for more heat and close it to make the fuel last longer.

I'll find the manual online and read it. The FAQs on the Morso site say this about temperature:

 

Quote

There is soot in my chimney. how did that happen?

If the temperature is too low you might experience tarry soot in your chimney. The combustion temperature will be too low if not enough air is supplied, compared to the amount of wood. Tarry soot is easily recognised as a brown sticky coat. Supply more secondary air to increase the temperature.

A stove flue thermometer placed on the lower part of the flue pipe will indicate if the air supply is correct. The flue gas temperature must be approx. 250°C. If the flue gas temperature is considerably lower, tarry soot may be created in the chimney. If the flue gas temperature exceeds 250 – 300°C, the inside parts might be superheated.

I don't have a stove thermometer but I do have an infrared gun thermometer, so I could use that to measure the temperature.

 

Next time smoke starts coming in I'll raise the temperature at the base of the flue to between 250-300 degrees and see if that impacts.

 

3 hours ago, Sea Dog said:

The only other thing that concerns me is the difference opening your doors makes. Are you sure there's not been a reduction in vent so the fire is being starved of air?

I'm not 100% sure that opening the bow doors did help, it could just be that more fresh air got in and diluted the smell. Around 3 months ago I did change the layout at the front which I thought may have reduced the airflow from the vent in the bow bulkhead. I opened that up after this conversation and I definitely feel a bit of a draught through it, so I thought that might have solved the problem - disappointed when I started smelling smoke again today.

 

2 hours ago, Tracy D'arth said:

You could always move off till spring into a flat with electric heating?

Giving up is always an option, yes! But then I'd have to live in a flat - I think I'd rather suffocate!

 

1 hour ago, Jen-in-Wellies said:

What is the horizontal distance between the flue and the nearest roof vent? Any chance you could post a photo of the stove and flue pipe inside the boat and the roof in the area of the chimney outside? May give us some clues that can help.

I'll take some photos the next time it happens during the day.

 

My boat is a bit unusual - it has a roof that overlaps over the walls, with a couple of mm gap the whole length of the boat. This provides ventilation in place of mushroom vents. I have considered silicone sealing along that edge near the chimney.

 

1 hour ago, Tony Brooks said:

Excel really stinks, i think its the petro-coke it contains. Red from the same maker smells far less pungent but is not certificated for smokeless zones but it does not smoke much once going. I could smell the Excel on my stove all over the garden and down the road and that is from a  house chimney. Certainly try another brand.

I've heard that Red is being taken off the market, don't know if that's accurate, but I can see if I can find it. Are there any other recommendations?

Perhaps another option is to switch to wood logs?

 

1 hour ago, sueb said:

What is the CO monitor reading?

I have 3 alarms of 2 different brands, but they all only show "alarm" or "no alarm", none of them have a reading. I will buy one that has a ppm reading.

[Jen-in-Wellies]

14 minutes ago, jetzi said:

I'll take some photos the next time it happens during the day.

 

My boat is a bit unusual - it has a roof that overlaps over the walls, with a couple of mm gap the whole length of the boat. This provides ventilation in place of mushroom vents. I have considered silicone sealing along that edge near the chimney.

Doesn't necessarily need to be when it is happening. Just a pictorial idea of the stove layout, inside and out. Not sure if the unusual top vent method has been mentioned before, for example and might well be significant. Over, say a 8m long cabin a gap between roof and sides each side will give 160cm² of top ventilation for each mm of gap. Each one of the four mushroom vents on my boats gives around 75cm² on a 12m long cabin, so each mm of gap you have is worth two mushroom vents roughly. Depends on the cabin length, which we don't know. A "few" mm might be a lot more than you think, leading to any bottom ventilation being totally overwhelmed by the top.

Jen

[MartinW]

Yesterday I was foolishly put in charge of an incinerator bin, effectively a perforated dustbin with a stubby chimney on top. It was very cold (My van said -3 when I started it) and still in the small garden area where I was working. There were some lovely effects from the smoke going up about a foot and then spectacularly cascading back to earth, filling the 'sink bowl' created by the hedge-borders. I was reminded of those old 'mushroom' fountains in the middle of sewage-works.

Some great advice in this thread for future amelioration but I reckon that most of what you are experiencing is a non-typical winter inversion made worse by the compromised nature of the flue in a boat. My home stove has a double-skinned chimney up above the first floor roof line and the smoke still behaves the same on cold, still days.

[Jen-in-Wellies]

11 hours ago, jetzi said:

My boat is a bit unusual - it has a roof that overlaps over the walls, with a couple of mm gap the whole length of the boat. This provides ventilation in place of mushroom vents. I have considered silicone sealing along that edge near the chimney.

Further to what I said yesterday evening, a small gap of only a couple of mm along the entire cabin length each side will give massive amounts of ventilation. You could safely block a lot of it in the region of the flue and still have adequate top vents. Measure the real gaps and their length, then work through the calculations in Appendix K of the Boat Safety Scheme private boats requirements for the cabin size, appliances and number of people and block off enough to give you the recommended amount of top vent.

Jen