Hello Alan4711,
I have a piazetta 905e mutlifuel wood burner and it puts out between 9-14 KWtt per hr. the only wood I steer clear of is soft wood (all conifers) as they create chimney tar which can ignite and treated wood. This little poem may help you choose your wood.
Beech wood fires burn bright and clear,
If the logs are kept a year.
Oaken logs burn steadily,
If the wood is old and dry.
But ash dry or ash green,
Makes a fire fit for a queen.
Logs of birch wood burn too fast,
There???s a fire that will not last!
Chestnut???s only good , they say,
If for long it???s laid away.
But ash new or ash old
Is fit for a queen with a crown of gold!
Poplar makes a bitter smoke,
Fills your eyes and makes you choke!
It is by the Irish said,
Hawthorn bakes the sweetest bread.
But ash green or ash brown
Is fit for a queen with a golden crown.
Elm wood burns like churchyard mould,
Even the very flames are cold.
Apple logs will fill your room,
With an incense -like perfume.
But ash wet or ash dry
For a queen to warm her slippers by!