Air intake for Multi-fuel stove

[alistair1537]

Hi All

 

The fit out continues...We are busy installing a Multi-fuel stove for our first winter on board - I want to draw air from outside the boat to feed the fire - I have the necessary attachment for the stove with damper control that exits at the rear. The duct pipe is 75 mm, so I am looking for a ventilation cover that be suitable for the through-hull.  Louvres preferred but I am fitting the ducting in a swan's neck arrangement to help reduce any chance of water ingress. The through-hull will be just under the gunnel rubbing strake, so the cover should not be proud of that point. I'd prefer a round brass fitting or stainless steel over aluminium or....galvanised.

 

Anyone know of a source for such?

 

Thanks in advance!

Edited September 14, 2020 by alistair1537
Wrong word used...

[Rickent]

drawing the air from inside the boat removes moisture and keeps the boat dry.

[Rob-M]

Why do you need to draw in external air...? What stove are you fitting...?

[alistair1537]

1 hour ago, Rickent said:

drawing the air from inside the boat removes moisture and keeps the boat dry.

Using the nice warm air from inside the boat that the fire has heated to fuel the same fire makes little sense - all you do is draft in "fresh air" from all the cracks and vents in the boat to replace the warm air you've allowed to escape up the chimney - the "fresh air" is likely to carry in as much moisture? 

 

On the other hand, directly using the "fresh air" via a ducted vent, circumvents the heating of it, and the heat from the fire keeps the boat nice and dry...

 

This is not a new practice - it has been done for ages.

Edited September 14, 2020 by alistair1537
added a word

[Bee]

There is another option, draw the air from under the floor, What happens beneath the floor is a mystery for most owners but sometimes it is damp and horrible, wood rots, steel rusts. Probably impossible to do any calculations for volumes but if you find a nice dark and cold corner, under a bed is a good place to start, and drill some big holes there you could achieve useful ventilation there and useful ventilation as air passes through the bilges and then duct it back up through the floor and into the fire. Easier than cutting a big hole in the side and much more useful.

[Higgs]

24 minutes ago, alistair1537 said:

Using the nice warm air from inside the boat that the fire has heated to fuel the same fire makes little sense - all you do is draft in "fresh air" from all the cracks and vents in the boat to replace the warm air you've allowed to escape up the chimney - the "fresh air" is likely to carry in as much moisture? 

 

On the other hand, directly using the "fresh air" via a ducted vent, circumvents the heating of it, and the heat from the fire keeps the boat nice and dry...

 

This is not a new practice - it has been done for ages.

 

You're not going to succeed in keeping the air contained in the boat. You'll require a certain area of ventilating points in the boat to satisfy the BSS standards. Circulation.  

 

 

[dor]

My stove is at the front of the saloon. There is a gap under the bow doors which will let in plenty of air.

 Better than cutting a big hole just above the water line, with or without a swan neck.

[Higgs]

 

When the Morso is on during the winter, my weather station tells me the humidity level inside could do with being higher. I get the grimaced face symbol. The humidity inside today is 74%. I've heard that Tom Jones always had a humidifying in his hotel rooms, set at 70%. In the winter, it can go down into the 20's, in the boat. 

 

 

 

[alistair1537]

9 minutes ago, Higgs said:

 

You're not going to succeed in keeping the air contained in the boat. You'll require a certain area of ventilating points in the boat to satisfy the BSS standards. Circulation.  

 

 

Certainly, There are vents in roof and doors to satisfy the requirements - the point of the ducted vent is to minimise heat loss through the chimney. 

[Dr Bob]

42 minutes ago, alistair1537 said:

Using the nice warm air from inside the boat that the fire has heated to fuel the same fire makes little sense - all you do is draft in "fresh air" from all the cracks and vents in the boat to replace the warm air you've allowed to escape up the chimney - the "fresh air" is likely to carry in as much moisture? 

 

On the other hand, directly using the "fresh air" via a ducted vent, circumvents the heating of it, and the heat from the fire keeps the boat nice and dry...

 

This is not a new practice - it has been done for ages.

Ventilation is key in the winter. Have you lived on a boat in the winter? How did you dry you clothes after washing? How do you cook without creating steam? The stove creates the circulation with a significant draw from the botttom caused by the air being sucked in. Cut that off and ventilation/ circulation is compromised. I cant recollect seeing a boat with the stove inlet piped to the outside. 

Edited September 14, 2020 by Dr Bob

[Higgs]

18 minutes ago, Dr Bob said:

Ventilation is key in the winter. Have you lived on a boat in the winter? How did you dry you clothes after washing? How do you cook without creating steam? The stove creates the circulation with a significant draw from the botttom caused by the air being sucked in. Cut that off and ventilation/ circulation is compromised. I cant recollect seeing a boat with the stove inlet piped to the outside. 

 

It could also be self-defeating without some form of a fan sucking in the air. The vagaries of the wind can otherwise cause the system proposed to be irregular and give an inconsistent flow. Until the flue is hot, the fire will not demand a flow of air caused by convection.  

 

 

 

Edited September 14, 2020 by Higgs

[mrsmelly]

2 hours ago, alistair1537 said:

Hi All

 

The fit out continues...We are busy installing a Multi-fuel stove for our first winter on board - I want to draw air from outside the boat to feed the fire - I have the necessary attachment for the stove with damper control that exits at the rear. The duct pipe is 75 mm, so I am looking for a ventilation cover that be suitable for the through-hull.  Louvres preferred but I am fitting the ducting in a swan's neck arrangement to help reduce any chance of water ingress. The through-hull will be just under the gunnel rubbing strake, so the cover should not be proud of that point. I'd prefer a round brass fitting or stainless steel over aluminium or....galvanised.

 

Anyone know of a source for such?

 

Thanks in advance!

Dont try to reinvent the wheel, it works very well. I am just entering my 31st winter aboard and I wouldnt do what you are wanting to do, listen to what the others have said. ?

[Tracy D'arth]

Even with a swan neck you run the very real risk of flue gas reversal in windy conditions, a crazy idea which has no place on a boat where the flue height is always insufficient anyway.

Just another unnecessary hole in the boat.

[blackrose]

1 hour ago, alistair1537 said:

Using the nice warm air from inside the boat that the fire has heated to fuel the same fire makes little sense - all you do is draft in "fresh air" from all the cracks and vents in the boat to replace the warm air you've allowed to escape up the chimney - the "fresh air" is likely to carry in as much moisture? 

 

On the other hand, directly using the "fresh air" via a ducted vent, circumvents the heating of it, and the heat from the fire keeps the boat nice and dry...

 

This is not a new practice - it has been done for ages.

 

I think you're right but it sounds like a hassle to do it on a narrowboat and I haven't heard of it being done before. I'll be interested to see your results if you can post a photo or two once it's done.

[blackrose]

2 minutes ago, Tracy D'arth said:

Even with a swan neck you run the very real risk of flue gas reversal in windy conditions, a crazy idea which has no place on a boat where the flue height is always insufficient anyway.

Just another unnecessary hole in the boat.

That's true as well. With just one air intake you run the risk of blockage, flue gas reversal, etc.

 

What you're doing is trying to create a room sealed stove and I can see the advantages of that, but which stove are you installing and is that installation to manufacturer's recommendation? 

[alistair1537]

46 minutes ago, dor said:

My stove is at the front of the saloon. There is a gap under the bow doors which will let in plenty of air.

 Better than cutting a big hole just above the water line, with or without a swan neck.

Yeah, I agree with that sentiment, cutting holes in boats seems to be a bad idea in general - I think maybe we'll duct through to the engine bay - there's a vent in there already to the outside. I note that Refleks air intake kits go through the roof like the chimney which is also doable, but means another potential leak point there too?

12 minutes ago, mrsmelly said:

Dont try to reinvent the wheel, it works very well. I am just entering my 31st winter aboard and I wouldnt do what you are wanting to do, listen to what the others have said. ?

If we all took that advice, we'll still be crossing rivers on floating logs...

[mrsmelly]

19 minutes ago, alistair1537 said:

Yeah, I agree with that sentiment, cutting holes in boats seems to be a bad idea in general - I think maybe we'll duct through to the engine bay - there's a vent in there already to the outside. I note that Refleks air intake kits go through the roof like the chimney which is also doable, but means another potential leak point there too?

If we all took that advice, we'll still be crossing rivers on floating logs...

Not realy as there are better methods. However what you are proposing is a retrograde step. Forums are great places to ask people with experience their views on an idea, when several have informed you many of which have huge experience that its not a good idea then its good to listen. Your choice, perhaps you can fit it next to your composting toilet?

[Tracy D'arth]

Ah, Leixlip is near Dublin, its the Irish way of doing things! ?

[ditchcrawler]

Its a diesel stove designed for boats, like the Dickinson which are were made to fit to fishing boats and they do recommend an external air supply, I think they are worried about them being in very confined areas with little ventilation. 

[Higgs]

40 minutes ago, alistair1537 said:

If we all took that advice, we'll still be crossing rivers on floating logs...

 

Let's face it, a boat is just fancier. 

 

 

[blackrose]

2 hours ago, dor said:

My stove is at the front of the saloon. There is a gap under the bow doors which will let in plenty of air.

 

 

It shouldn't really matter where your stove is located, or whether you've got a gap under the doors. Assuming there is adequate fixed ventilation on the boat then as it burns oxygen a stove in the centre of the boat will draw air in through the vents.

[Tony Brooks]

1 hour ago, mrsmelly said:

Dont try to reinvent the wheel, it works very well. I am just entering my 31st winter aboard and I wouldnt do what you are wanting to do, listen to what the others have said. ?

 

He is obviously set on his idea with little experience to base it on so lets encourage him to go ahead. If the BSS bod will accept that the stove can be disregarded in the ventilation calcs (by no means certain) then he will have even less ventilation that most and after a couple of winters with damp cloths and mould etc. he may learn

[TheBiscuits]

2 hours ago, Tracy D'arth said:

Even with a swan neck you run the very real risk of flue gas reversal in windy conditions, a crazy idea which has no place on a boat where the flue height is always insufficient anyway.

Just another unnecessary hole in the boat.

 

As well as this, I'd be concerned that mooring with the combustion air intake against the bank would restrict it half the time the boat is moored.

 

2 hours ago, alistair1537 said:

I think maybe we'll duct through to the engine bay - there's a vent in there already to the outside.

 

That would be better, especially if there are vents both sides.  I still think it's the wrong thing to do on a boat for all the reasons posted above, but at least this way you won't have to weld another hole up when you remove the ducting after trying it for a few weeks.

[Rickent]

2 hours ago, Dr Bob said:

Ventilation is key in the winter. Have you lived on a boat in the winter? How did you dry you clothes after washing? How do you cook without creating steam? The stove creates the circulation with a significant draw from the botttom caused by the air being sucked in. Cut that off and ventilation/ circulation is compromised. I cant recollect seeing a boat with the stove inlet piped to the outside. 

we dry all our wet clothes around the stove in winter, the stove draws the damp out.

Drawing air from outside is crazy.

Never had a problem with condensation. 

[blackrose]

59 minutes ago, Tony Brooks said:

 

He is obviously set on his idea with little experience to base it on so lets encourage him to go ahead. If the BSS bod will accept that the stove can be disregarded in the ventilation calcs (by no means certain) then he will have even less ventilation that most and after a couple of winters with damp cloths and mould etc. he may learn

 

Perhaps, or on the other hand the reduced ventilation may be perfectly adequate for his boat and the system may work well, in which case he might give us some feedback so that we can all learn something new.

 

It often pays to keep an open mind rather than belittle people with new ideas.