Burning wood on woodburner and multifuel stove - much difference?

[andy cobb]

2 minutes ago, Stubby said:

I think it needs the air source from above for wood ideally .  It sounds like its burning well though . If you mean by  "efficiently " burn less wood then I'm not sure that is achievable as the " burning " seems efficient as it is ...

Your quite possibly right, to be fair it tends to get fed softwood and the ugly hardwood lumps that won't sell for firewood.

[openspaceman]

2 hours ago, andy cobb said:

We have a charnwood la 45 multi fuel stove with back boiler, it does warm water and 9 rads. It's designed to run on anthracite I think but it hasn't seen a lump of coal in 8 years. The only air source is from underneath via a self moderating air vent. Is there anyway of making it more efficient when using purely wood as it can work its way through a good sized wheelbarrow of wood in a day.

Thanks - andy

If it's a multifuel stove then it can burn coal or wood and that coal can be anywhere between  bitumous to nearly pure carbon in anthracite. Even peat will burn if dry.

 

The difference is that when burning wood you drive off volatiles that  have to burn in a flame above the firebed, with anthracite you have to gasify the carbon to carbon monoxide and then burn that above the firebed, so wood tends to need 5 times more air for burning the volatiles whereas the  coal needs similar amounts below the firebed  for gasification as it needs above to burn the gases.

 

Your stove is putting a lot of heat into the water compared with the heat into the room, what makes you think it is inefficient?

 

If you have dry fuel the only losses in efficiency are in the heat that exits the flue. These will be sensible heat (e.g. what is the temperature of the exhaust gases up the chimney) and the massflow up the chimney (e.g. is too much excess air or unburnt gases going up the chimney). If you see a lot of whitish yellow smoke then the wood is either smouldering or too wet. Blue smoke and your flame is being quenched somehow, black smoke not enough secondary (over the firebed) air.

[andy cobb]

On 11/07/2019 at 22:18, openspaceman said:

, black smoke not enough secondary (over the firebed) air.

That's the only issue with the stove, it only let's air in below the grate. As for smoke, once it's up to temperature it's hard to tell that the stoves even lit.

For the work it does its probably quite efficient , especially for its age (approx 30) 

Think I was hoping to improve fuel consumption , but it wasn't until I started counting radiators to write the post that I realised just how much it was doing, and even then I got it wrong coz I forgot the towel radiator so it's running 10 rads and providing warm water for washing machine and bath etc, so maybe a wheelbarrow full isn't too bad after all.