wood burner kw output to room size

[paul1966]

at the moment we have a coal fire but would like to replace it with a wood burner, there is a Burley 9104 4kw output for sale locally at a reasonable price but i am wondering if the output might be too low for the room size which is 23ft x 12ft. any thoughts?

[philm]

http://www.stovesonline.co.uk/calculator.asp

[andypaint]

Probably be better with a 7 or 8 kW and not running it as hard. A 4kw would take tiny logs that wouldn't last 5 mins.

[figgy]

4KW would heat the area no problem,to the point you would be opening doors to let heat out after the initial heat up.

 

The biggest thing to look at is how efficient the log burner is and how controllable the heat is. My log burner is five KW rated and its in a big room kithchen diner with sitting room, we end up turning it down low and opening the doors to other rooms to let out the heat.

Edited November 20, 2016 by figgy

[12borebanger]

Don't get an oversized burner. If the heat output is too much for the room you'll end up over heating and trying to dampen the fire, you'll just end up with smouldering logs which is no good for your chimney/liner.

[paul1966]

this one is 89.9% efficient and with it being small only burns one log at a time so wood should last a while. i am going to look at the cost of installing a flue liner before making a final decision and either sticking with the coal open fire or changing to a wood burner.

[Yellow Bear]

this one is 89.9% efficient and with it being small only burns one log at a time so wood should last a while. i am going to look at the cost of installing a flue liner before making a final decision and either sticking with the coal open fire or changing to a wood burner.

The question you need to ask yourself is "how long will it take to pay for the installation in fuel savings" bearing in minds the efficiency of an open fire is less than 30% not to mention that the burner requires less work to maintain in "fire"

[old man]

4KW would heat the area no problem,to the point you would be opening doors to let heat out after the initial heat up.

 

The biggest thing to look at is how efficient the log burner is and how controllable the heat is. My log burner is five KW rated and its in a big room kithchen diner with sitting room, we end up turning it down low and opening the doors to other rooms to let out the heat.

My experience too.

 

A useful back up is smokeless coal as running on wood alone can be a pain unless plenty available.

Don't forget the cost of logs, the stacking and splitting etc.

 

Could be useful for when the electric goes off?

[Stonepark]

Your room really requires a 5kw to 6kw but even a 4kw will heat the room significantly more than a standard 16" open fire for a lot less fuel.

 

You are better running a smaller stove at maximum rather than a larger stove at 75% s as efficiency decreases once you are burning a less full fuel chamber.

 

I used to have an 8kw stove (with in built back boiler using 2.5kw of the output) and it still could cook a 15ft by 15ft room with wood.

[paul1966]

been looking on ebay at the flue kits, probably looking at around £200 for the parts, just need to find someone to drop the liner down the chimney and make good, then i can do the rest.

[Adge Cutler]

been looking on ebay at the flue kits, probably looking at around £200 for the parts, just need to find someone to drop the liner down the chimney and make good, then i can do the rest.

How old is the existing chimney ? If you have had a coal fire ( Class 1 fire ) regularly without any leakage into the rooms upstairs and the chimney is airtight, you may not need a flue. Just a short length ( 1.0m ) of flue pipe.

 

Remember the co alarm and combustible air supply ( air brick too ) or the installation wont comply with Building regs.

[Medic1281]

I was under the impression that 5kw or under doesn't need an air brick in the room.

[paul1966]

I was under the impression that 5kw or under doesn't need an air brick in the room.

i think in an older house you do not, ours was built in 1950 so we probably won't need one.

[Adge Cutler]

I was under the impression that 5kw or under doesn't need an air brick in the room.

Depends very much on the Air permeability of the existing building, gaps under doors window vents etc. I believe all the information is on the planning portal document J. For properties with an air permeability > 5.0m³/h.m²300mm² of ventilation should be provided for each kW up to 5kW. Obviously it would be silly to have a AP test carried out when installing such a small output stove and might be just a question of trial an error ie see if the stove burns and the flue draws well without having to resort to opening a door or window.

 

 

 

i think in an older house you do not, ours was built in 1950 so we probably won't need one.

About 1950 is suspect a rebated terracotta flue liner was used as well, stick a torch up the chimney and check. No need to waste money on a flue if you don't need it.. After all a stove is only a firebox with a reduced aperture flue.

[Bazooka Joe]

at the moment we have a coal fire but would like to replace it with a wood burner, there is a Burley 9104 4kw output for sale locally at a reasonable price but i am wondering if the output might be too low for the room size which is 23ft x 12ft. any thoughts?

 

I've a 5kw Morso multifuel in a room slightly bigger than yours & it's ideal, but I burn coal not logs, it makes all the difference heat wise.

[Dougy]

I was under the impression that 5kw or under doesn't need an air brick in the room.

 

We have not long had 2 new doors, front and back, they were both rather draughty wooden doors before, trust me if you have double glazing and UPVC doors you will need an alternative air supply.

[njc110381]

Our room is about 16ft square and 8ft ceiling. We had a 3kw Stovax in there that running flat out could make the room just comfortable in the worst winters. I now have an 8kw Clearview 500 (I've no shortage of wood and it saves cutting it so short) and in an hour that can make the room unbearable. If we leave the door open so the heat can go upstairs and run it at about half output it still burns cleanly, doesn't clog the flue and warms the whole house.

 

My advice would be don't buy too small. Those tiny things are a ball ache! With the 8kw I can get enough wood in there to burn all night. That's not great for the flue or burn efficiency but if you count the time you spend lighting it vs cleaning the chimney twice a year it's a no brainer for me.

[Evilv]

The HETAS people claim all kinds of woes will fall on you if you don't have them install a flue and the fire. they talk about 'illegal' and stuff like that and talk about insurance claims being rejected as well as problems selling the house if there isn't a professionally installed stove.

 

I was helping an old farmer pal of mine with his stove last week. We took out his old steel chimney liner which was a ten inch stainless pipe he'd installed twenty five years ago for his open fire and he had bought new liner and all the bits to go with his new 8 to 12 kw stove (which seems massive to me to be honest). Anyway - the supplier of the stove put the wind up him that much that he has asked a HETAS registered company to come and do the install and they are charging him £750 cash. I wouldn't care - the brand new liner is already in the chimney, the old guy is supplying all the parts except he needs a new pot and cowl because the old one fell apart while he was dropping the new pipe down, but that seems steep to me.

 

The big difference between a new stove and an open fire is that when you turn it down and restrict the air entering the stove IT WILL GENERATE carbon monoxide. If the flue isn't right, that could leak into the house and do someone a bad mischief or worse. You must make sure that the flue is properly sealed and that there is enough air getting into the room where the stove is. You probably know all this already though.

Edited November 20, 2016 by Evilv

[oowee]

My lounge is 550 sqft with a max height of 15 ft well insulated and i run a 5kw stove which does this and the rest of the house too.

the performance figures of the stove are misleading (IMO) as they refer to its burning performance not use able heat. I have the fresh air supply flued direct to the fire (closed system) so I don't have cold air entering the house to feed the fire. Its efficiency remains the same at 81% but provides much more warmth than otherwise.

[Jason_ox]

We are just having a 6-7kw installed in our bothy on the Isle of Mull with similar room dimensions to yours. We had a 4-5kw and it just wasn't enough, probably down to low insulation more than anything else but not a lot you can do with solid stone walls.

[bornfree]

I have an 8kw in a similar sized room. Its absolutely fine with the hall door open so heating other parts of the house.

[dazb1967]

 

We have not long had 2 new doors, front and back, they were both rather draughty wooden doors before, trust me if you have double glazing and UPVC doors you will need an alternative air supply.

You don't need vents for a 5Kw burner, we had one fitted recently by a HETAS certified installer and no vents were required, I installed a log burner in my previous house myself and it was fine but I heard too many horror stories about void insurance etc so I went down the registered route.

From memory anything above 7kw requires extra ventilation

[vampire]

We have a 4kw in a slightly wider than standard fire place,it heats the sitting room easily which is 4.8 x 5.8m and no air vent installed with upvc double glazed and fully insulated bungalow.

Only problem is you need smaller split logs,but as I am a builder every thing gets burnt in there,at £200 for a new flue I don't care how long it lasts.

[Dougy]

If your home is sealed due to double glazing and UPVC doors you WILL need some ventilation. Makes no difference what size the fire is, it will eventually burn the oxygen in the house.

That's one of life's simple facts, fire needs an oxidising agent to burn and in this case it's oxygen. Once that's all gone you're breathing in co2.

[Adge Cutler]

You don't need vents for a 5Kw burner, we had one fitted recently by a HETAS certified installer and no vents were required, I installed a log burner in my previous house myself and it was fine but I heard too many horror stories about void insurance etc so I went down the registered route.

From memory anything above 7kw requires extra ventilation

 

It depends very much on the age of your property to be honest. If its a modern property ( since about 2008) which is generally airtight ( double glazing, vapour barriers, weather sealed doors etc ) you will need one which is equivalent to 500mm2 per KW. (I think its 500 I will check tomorrow at work ))

 

If your house is older, generally not to current air leakage standards you will still need one for a fire over 5KW but the first 5kw is discounted.

 

However Nobody goes to the trouble of having APT's done on older properties.. why should they ?

 

The problem lies where home owners with older properties have taken measures to reduce air permeability to conserve fuel and power and made the need for ventilation necessary. In this situation the individual registered installer must decide whether it is required or not and it comes down to a question of interpretation.

Edited November 20, 2016 by Adge Cutler