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Woodburning Stove - Internal / External Air?


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Hi all!

 

I'm looking to get a woodburner for heating my open plan living room / kitchen - but have come across some conflicting advice...

 

I am looking at the MEG 4.5 / 7.5.

 

I wanted to know what the benefits / disadvantages were for using an external air supply. The MEG 7.5 can accept an external air supply - or use internal air with of course the provision of an air brick.

 

I have read that if you use a direct air supply from outside - stoves become less controllable and always burn the wood much faster - so you would end up using much more wood stock - or burn out quicker.

 

That said I have also read that not having an external supply - the stove would be sucking in already warmed air from the room - and it would get replenished by external cold air from wherever it can get in the case of a MEG 4.5 - or via the air brick for the MEG 7.5.

 

Can anyone comment if they have had experience of both external / internal air supplies?

 

Thanks!

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A piece of wood contains only so much energy, how fast you release that energy will depend on how much air you put into the stove, that should depend on the position of the secondary air supply lever, this is the air curtain down the inside of the glass.

 

All the stoves I sell that have a direct air facilty have a controlable opening so that you control now much air enters the stove and therefore how fast and hot it burns.

 

Think of it as an engine inlet manifold that fits over the existing air inlet, normally the stove would draw air from the room, with an outside air kit any air required is drawn from the manifold which connects to the air vent. The existance of the outside air supply should in no way impede the way the stove is controlled, its simply an air supply that is used as and when directed by the operator.

 

This means that there is no drafts from the air vent entering the room. New houses are all tested for air tightness, all stoves fitted in such houses need to be in rooms with either an air vent or the stove must be fitted with a direct air supply that is connected to the air vent.

 

Under the building regs older properties require air vents only when the stove has a capacity of 5.1kw or above. 5.0kw and below do not require an air vent.

 

Regarding the stoves, cant say I have ever heard of either, perhaps you could post a link. 4.5 I assume is 4,5kw output, enough for a 63 cu m room assuming average insulation, 7.5kw would do a 105 cu m room assuming average insulation, thats a pretty big room. It is far better to drive a small stove hard that have a big one ticking over, more flames, less soot and tar. My calc's are based on the Morso size table, getting a 21 C temp rise in the room if its 1 C outside.

 

I have just installed a direct air kit on my own Morso Panther 8kw, works well, it is a sensible way forward as it prevent heat loss through an open vent.

 

Hope that helps.

 

A

Edited by Alycidon
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Thanks Alycidon :001_smile:

 

House is a bungalow. The living room is open plan with the kitchen. The combined volume is 101 M³. Insulation is to current standards. The combined heatloss calcs come to 4.2kw.

 

I had thought of leaving the door open to the hallway which is 24 M³ - which serves three beds & bathroom.

 

I take your point about driving a smaller stover hard. I am just wondering whether I will get draughts from somewhere if I go for the 4.5kw stove with no air brick? The air will have to come from somewhere - or do they not require much air?

 

The stoves are DEFRA approved (I'm in a smokeless zone) - details here:

 

Meg + Sirius smokeless wood and coal stoves

 

I have seen the 4.5 in operation and it's seemed very good - certainly throwing a lot of heat out.

 

Thanks again

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If your heat loss is 4.2kw just to keep the room at a constant temp then you need more than that to raise the temp.

 

One other thing to consider is, that the house needs so many air changes per hour any way so having some of that feeding the stove should not be a big issue. It will also help reduce condensation & damp issues.

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Thanks Alycidon :001_smile:

 

House is a bungalow. The living room is open plan with the kitchen. The combined volume is 101 M³. Insulation is to current standards. The combined heatloss calcs come to 4.2kw.

 

I had thought of leaving the door open to the hallway which is 24 M³ - which serves three beds & bathroom.

 

I take your point about driving a smaller stover hard. I am just wondering whether I will get draughts from somewhere if I go for the 4.5kw stove with no air brick? The air will have to come from somewhere - or do they not require much air?

 

The stoves are DEFRA approved (I'm in a smokeless zone) - details here:

 

Meg + Sirius smokeless wood and coal stoves

 

I have seen the 4.5 in operation and it's seemed very good - certainly throwing a lot of heat out.

 

Thanks again

 

 

Stoves look nice, made in England as well which is a big plus.

 

So 101 cu meters of space to heat in a well insulated property, divide volume by 16, ( 14 for average ins, 12 for poor), that comes back at about 6kw. On that basis the 7.5 might be a bit big but if you have a conservatory or similar to bleed excess heat into when required it should be ok. But as a secondary heat source the smaller one might be a better bet. If the sitting area is close to the stove and TV which most are then I would err towards the smaller stove, you want to see lots of flame but dont want to be mega hot.

 

A

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Hi

 

Thanks for the replies :-)

 

The room will be heated by fast acting aluminium radiators and will be a zone in itself with thermostatic control - so as the stove heats up the radiators will shut down.

 

Yes the stove will be a side focal point in a seating area - so it would be nice for it to be in flame so to speak without us being fried to the seats :gasthrower:

 

I was told the stove outputs are nominally rated - so at full pelt it would be more like 6Kw.

 

So - looks like the 4.5kw will do the job :thumbup1:

 

Thanks

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