please advise re: output rating, does size really matter?

[freyah]

hello

first post here and I'd really appreciate any advice.

Am doing my research before getting our first woodburner and am not sure what to do on size. The output calculators say I need 4Kw but husband is suggesting we get a 6Kw "just in case" also hoping that we can use bigger logs.

Is this a wise idea? particularly given that anything above 5Kw rating will need external venting

My thinking is that you are best to run your stove near it's capacity to get best efficiency, is this true?

many thanks

 

[Highbeam]

Your husband is right. You never want to plan to use a machine at 100% capacity all the time. Efficiency will go down as you approach max output as you will be pumping large amounts of heat through the vent.

 

[par0thead151]

Your husband is right. You never want to plan to use a machine at 100% capacity all the time. Efficiency will go down as you approach max output as you will be pumping large amounts of heat through the vent.

i wish i could have gotten a larger fixre box.
mine fills up with ash and coals fairly quickm, as it is only 2.5 cubic feet in size.
get the largest size you can afford.
you can make a small fire in a large firebox, but you can not make a large fire in a small firebox...

 

[Pagey]

How many square feet are you heating? In what type of climate? And do you want to use it for primary heat or just weekend burning?

 

[freyah]

thanks for replies guys

my room is 13'9 x 15'8 with a ceiling height of 9'2 we have cold wooden floors, double glazing, one external wall (stove would be on internal wall between us and neighbour)

The required vent for 5Kw+ stoves was putting me off as this room is freezing already! Your advice makes sense though

We are supplementing our Gas Central Heating, hoping that we can switch off heating downstairs in the evening.

 

[Wood Duck]

I assume when you say outside venting, you mean a vent that allows the stove to use outside air for combustion, right? This is what we call an Outside Air Kit (OAK) in the US. Lots of people like these because they help limit cold air leaks into the room caused by the stove pulling room air up and out the chimney, which is replaced by cold air from outside. Many people will recommend an OAK even if it is not required. I don't really know enough about them to have an opinion.

 

[freyah]

that's exactly it Wooduck, we're supposed to have a non blockable vent in wall or window letting fresh air in. This applies to every stove over 5Kw and increasing with the output of the burner

all the best

 

[Highbeam]

Okay, so, 4000 watts is only a 13,648 btu per hour. This is a tiny stove compared to my 2.3 CF heritage that makes 55000 btu to heat my 1700 SF home. The heritage is mid sized here in the states and is a 16KW heater.

It's not the size of the room that was asked, it is the size of the home. How big is your home?

 

[freyah]

sorry for misunderstanding

my home has 2 similar sized public rooms downstairs (see measurements in last post) a and very cold tiny kitchen with no heating. Upstairs we have 3 bedrooms and one bathroom, we are attached to a neighbour on one side and have a gas boiler heating the radiators.

 

[woodgeek]

In practice, smaller wood burners have much shorter cycles--you'll be tending it ALL the time. Better to get a larger unit, which can still run small ambiance fires, or when you want the heat, larger fires with longer cycle times. The issue then is overheating a single closed off room.

So, the next question is: if you left doors open, how much total floor square footage (or meters if you prefer) could the heat circulate to, assuming it will only flow to rooms on the same level or above? If this figure is large, you could get a sensibly larger unit, not worry about getting over-heated, and make a bigger dent in your gas bill.

Also, how many thermostats do you have, and if only one, where is it?

 

[freyah]

so the advice is to go for a larger burner which I'm happy to do, thanks for the help.

Now.....I'd be very interested to know how to calculate how far the heat would spread with the door open? We have 6 radiators in the house and all have thermostatic controls. we have a HUGE gas bill, mainly (in my op) due to the very draughty wooden floors downstairs and would love to try and cut this down.

we are thinking of laying a new sealed bamboo floor on top of the boards to insulate and reduce draughts (though will not have the money for that for probably another year)

appreciate these words of experience.