Wind, Stove Blow Back & CO

[pearley]

Bought a second CO monitor a couple of months ago to fit in the lounge, to supplement the one in the bedroom. It went off last week during the day in the last lot of high winds so shut the fire down and opened doors then relief fire when the wind had subsided. 

It went off again this morning at 7.15am, the fire was on tick over but the lounge area set a bit fume so again have shut the fire off (whilst doing this a short blast of flame came through the vent) and vented the cabin. 

Now we are moored by the Sea Life Centre since in a bit of a canyon so you don't know from which direction the next blast of wind is going to come from. Are you better moored more in the open? Is a longer chimney better? (We have a standard 12 " one) Is it better with the vent fully open or almost shut? 

Unfortunately you don't really get much chance to experiment. 

[Alan de Enfield]

I have read that having a 'wirly gig' on top of the chimney (like a small roundabout with 'vanes') that rotates in any wind direction will cause an improved suction and keep all the bad stuff from blowing back.

 

This sort of thing (other makes and designs are available)

 

[mrsmelly]

9 minutes ago, pearley said:

Bought a second CO monitor a couple of months ago to fit in the lounge, to supplement the one in the bedroom. It went off last week during the day in the last lot of high winds so shut the fire down and opened doors then relief fire when the wind had subsided. 

It went off again this morning at 7.15am, the fire was on tick over but the lounge area set a bit fume so again have shut the fire off (whilst doing this a short blast of flame came through the vent) and vented the cabin. 

Now we are moored by the Sea Life Centre since in a bit of a canyon so you don't know from which direction the next blast of wind is going to come from. Are you better moored more in the open? Is a longer chimney better? (We have a standard 12 " one) Is it better with the vent fully open or almost shut? 

Unfortunately you don't really get much chance to experiment. 

Sounds to me like you may also have partial chimney blockage. Our alarm went off a couple of winters ago and that was the reason. Wind blows occasional puffs into our boat on bad days but alarm doesent trigger from the smoke so I believe you may have a blockage?

[pearley]

I'll pull the chimney off and look but it does get cleaned every autumn. Our Boatman Stove doesn't have a baffle plate so no possibility of ash buildup there. 

[Phil Ambrose]

ZThe answer to blow back is simple, look at all the fishing boats that have heating from drip feed or solid fuel fires, they generally have a H chimney  .

In my last boat I fitted a drip feed heater which came with a H chimney, never had any blow back issues .

On our present boat I changed from a double skinned chimney after suffering blow back and fitted a H chimney, result no blow backs.

Phil  

[bizzard]

Thems are downdraught diverters, They do a similar job as the ones on gas hot water heaters, geysers do.

[Phil Ambrose]

Weĺl Biz, whatever they are called, they work 

Phil 

[John Hartley]

Why would you purchase a second hand CO alarm. I do not understand that.

Just reread OPs post, my mistake sorry

 

Edited February 1, 2018 by John Hartley
Rereadfirst post

[nbfiresprite]

Just now, John Hartley said:

Why would you purchase a second hand CO alarm. I do not understand that.

 

He brought a second one, not a second hand one.

[John Hartley]

I know. I can only plead bad eyesight lol

 

[nbfiresprite]

7 hours ago, pearley said:

I'll pull the chimney off and look but it does get cleaned every autumn. Our Boatman Stove doesn't have a baffle plate so no possibility of ash buildup there. 

You should sweep it more often, if the fire is in dally use, My own is sweeped weekly.

[nb Innisfree]

The alarm on Innisfree kept indicating low level CO, turned out to be short chimney letting smoke curl downwards into a mushroom vent when wind was blowing in a certain direction. Longer 30" chimney sorted it. 

[markgregoryuk2000]

A friend has had smoke puff out of the vents on windy days, for him a longer chimney fixed the problem.

[blackrose]

I've had the same Vedetta cowl on my boat for about 12 years. Never had any back draft, blow back, or whatever you want to call it. I think it's essentially an H cowl in the form of a cylinder and personally I prefer it to a revolving cowl as it has no moving parts. I've never used a revolving cowl so I might be wrong, but I can't help thinking that they might actually restrict the draw in calm weather and be more suited to buildings which have chimneys a bit higher up than a boat.

When I sweep my chimney and flue I just stick a hose into the upturned Vedetta and give it a good flush through with water.

Edited February 10, 2018 by blackrose

[Guest]

56 minutes ago, blackrose said:

I've had the same Vedetta cowl on my boat for about 12 years. Never had any back draft, blow back, or whatever you want to call it. I think it's essentially an H cowl in the form of a cylinder and personally I prefer it to a revolving cowl as it has no moving parts. I've never used a revolving cowl so I might be wrong, but I can't help thinking that they might actually restrict the draw in calm weather and be more suited to buildings which have chimneys a bit higher up than a boat.

When I sweep my chimney and flue I just stick a hose into the upturned Vedetta and give it a good flush through with water.

That is identical in design to the one fitted to our stove flue at home (all be it ours is on a slightly bigger scale). No blow backs here either. I asked our HETAS fitter what it was for and the reason given was indeed to help prevent airflow back down the chimney in high winds.

 

Edited February 10, 2018 by MJG

[mark99]

Depending upon model, you can have a clean chimney bore but still have a blockage.

Best to strip out everything (dismantle) from stove and check.

Mine for instance has a steel plate above chimney exit from stove and this can hold a kilo of two of rust, soot etc.

 

 

Edited February 11, 2018 by mark99

[blackrose]

2 hours ago, mark99 said:

Depending upon model, you can have a clean chimney bore but still have a blockage.

Best to strip out everything (dismantle) from stove and check.

Mine for instance has a steel plate above chimney exit from stove and this can hold a kilo of two of rust, soot etc.

A steel plate above the chimney [you mean flue?] exit from the stove? Is that some sort of butterfly valve in the flue? They aren't recommended for the reasons you state. 

If on the other hand you mean a baffle plate at the top of the stove under the flue, Pearly has already said that his stove doesn't have one.

Anyway, a sensible stove/flue installation really shouldn't need to be dismantled to sweep and clean it out.

On 01/02/2018 at 10:25, pearley said:

I'll pull the chimney off and look but it does get cleaned every autumn. Our Boatman Stove doesn't have a baffle plate so no possibility of ash buildup there. 

 

Edited February 11, 2018 by blackrose

[brassedoff]

I use to struggle with blowback so I bought a brush.  :-/

[mark99]

Yes baffle plate that's it.  Unlatch it to remove. Acorn stove. Can dismantle the grate and guard to get every bit of ash out.

[Sir Nibble]

wind, stove, blowback and co. Sounds like a firm of solicitors.

[MtB]

On 01/02/2018 at 09:28, Alan de Enfield said:

I have read that having a 'wirly gig' on top of the chimney (like a small roundabout with 'vanes') that rotates in any wind direction will cause an improved suction and keep all the bad stuff from blowing back.

 

This sort of thing (other makes and designs are available)

 

 

Is there any evidence these actually DO anything, other than spin round in the wind and look pretty? 

While the Bernoulli principle partially explains how/why the H cowls work, it doesn't really apply to one of these.

[mark99]

Venturi or Bernoulli?

[MtB]

On 11/02/2018 at 21:24, mark99 said:

Venturi or Bernoulli?

 

The way a venturi works is explained by Bernoulli.

[WotEver]

16 hours ago, Mike the Boilerman said:

Is there any evidence these actually DO anything, other than spin round in the wind and look pretty? 

This site simply states that because it’s spinning the wind can’t get down the chimney. 

http://www.fluesystems.com/shop/Chimney_Cowls_Revolving.html

[MtB]

49 minutes ago, WotEver said:

This site simply states that because it’s spinning the wind can’t get down the chimney. 

http://www.fluesystems.com/shop/Chimney_Cowls_Revolving.html

 

Oh very scientific! 

I bet I could demonstrate otherwise.