New Wood burner !

[face cord]

how do you check efficency??

 

Some useful info:

 

http://www.soliftec.com/efficiency.htm

 

Stove efficiency

 

90% efficient wood stove (NB stove...not boiler)

[Paul Smith]

The Dowling stoves are all steel and very efficient.

[Woodworks]

Some people don't rate steel stoves (like the burley) compared to cast iron (like the handol), as they say they don't last as long dunno its thats true or not etc?

 

I have seen no evidence of this being true. I know of several older Woodwarm and Clearviews that show no signs of corrosion.

 

I am seriously thinking of replacing our cast iron Saey Scope with one of these Burley stoves but can't decide what size model to look at. The Saey is rated at 12kw max but frankly is to powerful for our house unless it's -10, I was thinking of the 8kw version but Stubby's comment about how much heat they give out has got wondering if we could go down to 5kw

 

Thanks for this thread it's good to read about new stoves and how good/bad they are

[likeitorlumpit]

Some useful info:

 

Solid Fuel Technology Institute - Efficiency

 

Stove efficiency

 

90% efficient wood stove (NB stove...not boiler)

 

Very interesting- if you're a bit geeky= like me

Important to note that high efficiencies often mean less waste heat going up the chimney meaning the flue is colder which could contribute to condensing gasses. Sometimes overridden by using an electric fan. This obviously affects the energy input and ultimate efficiency.

Difference in gross and net efficiency- net being about 10% less than gross.

1kg of wood= 5kw at 100% efficiency

I'm very happy with a 72%nett efficiency stove giving about 4kw of heat per kg of wood. I guess that would cost about 50 pence in electricity(not really sure what electric costs). Chopping logs has even more reason.

[Stubby]

Is that a 6 inch flexi liner or a rigid one please.Also did you have to put infill around the pipe.

 

Its a flexible stainless liner and is sealed where it enters the spigot of the stove the passes up the original terracotta liners in the chimney (7,5 inch) and attaches to pot at the top with a standard cowl to stop the rain coming down . No infil needed.

[Stubby]

Some people don't rate steel stoves (like the burley) compared to cast iron (like the handol), as they say they don't last as long dunno its thats true or not etc?

 

I have seen no evidence of this being true. I know of several older Woodwarm and Clearviews that show no signs of corrosion.

 

I am seriously thinking of replacing our cast iron Saey Scope with one of these Burley stoves but can't decide what size model to look at. The Saey is rated at 12kw max but frankly is to powerful for our house unless it's -10, I was thinking of the 8kw version but Stubby's comment about how much heat they give out has got wondering if we could go down to 5kw

 

Thanks for this thread it's good to read about new stoves and how good/bad they are

 

I liked the look of the 8kw Burley Brampton . Its basically the same as my Hollywell but wider . ( gives a sorta "wide screen tv aspect ratio to the window ) but I did the room calculation and it would have been too much . As it is the door to the stairs is open and the arch way to the back room is open so it is doing more than the room its in .

[openspaceman]

Very interesting- if you're a bit geeky= like me

Important to note that high efficiencies often mean less waste heat going up the chimney meaning the flue is colder which could contribute to condensing gasses. Sometimes overridden by using an electric fan. This obviously affects the energy input and ultimate efficiency.

Difference in gross and net efficiency- net being about 10% less than gross.

1kg of wood= 5kw at 100% efficiency

I'm very happy with a 72%nett efficiency stove giving about 4kw of heat per kg of wood. I guess that would cost about 50 pence in electricity(not really sure what electric costs). Chopping logs has even more reason.

 

I'm dubious at how these efficiency figures translate to actual use, they seem to work on the difference between the heat in a piece of dry wood and the flue losses in the enthalpy of the flue gases and again assume near stoichiometry. In practice as you increase moisture content then excess air increases so the flue temperature is distributed over a much higher mass flow. Also it looks like they can use a spot measurement which doesn't allow for the time constant on a massive stove. They assume smokeless combustion, as smoke is unburnt particles and represents a loss of fuel.

 

I think the adiabatic flame temperature of dry wood is 1600C

and 1kg of wood would need 4.5kg of air for stoichiometric combustion, so a total mass flow of 5.5kg. As a first approximation, because I haven't time to work out the specific heats of CO2 H2O vapour , Nitrogen and Oxygen at typical discharge temperature of 150C, I'll use a specific heat of air at about 1kJ/deg K. I also assume an ambient temperature of 0C.

 

If we call the 5.5kg at 1600C losslessly discharged at the flue as 0% efficiency then burning the same piece of wood at 25% moisture content,150% air and a flue exit temperature of 150C then we have a mass flow of 1*1.25+4.5*1.5=8kg

 

Energy from first example lost up chimney = 5.5*1600*1kJ and from second =8*200*1kJ

 

which gives an efficiency of 81%, anyone care to refine on that?

 

The last big (500kW) installation I monitored was running at 10% Oxygen in flue gas with 44% mc woodchip and a flue gas temperature of 180C and I would think this was a typical real world figure and 78% efficient.

 

I too would be happy with 72% actual heat ending up in the room from a small stove. With electricity at around 12p/kWhr and 100% delivered into the room that piece of wood is saving 43p which values it at ~£430/tonne

 

Mind you'd be better using the electricity in a heat pump cutting the cost to 1/3 at today's temperature here.

[Garfield]

Thanks for the reply Stubby,we have a Villager stove with boiler.On the second one now,boiler leaking after 18 years.