Heating value
77
depends on whether the wood is unsplit round logs,
metre-long split logs, or ready-to-burn split logs, and
on whether it is fresh from the forest or dried for
firewood.
The wood volume stays constant from when it is
freshly cut with a moisture content of 60% to the fibre
saturation point at 25%. The wood starts to contract if
dried below this point. It shrinks, and this is why air-
dried wood (moisture content of 15%) has more wood
substance per stere than freshly cut wood. The
difference is typically 5% to 6% for softwood, and 6%
to 9% for hardwood.
Logs are not straight. The longer the logs are, the less
wood and the more air is present per stere. There is
typically more air in "crooked" hardwood than in
"straight" softwood.
There is one further difference: round logs can typically
be stacked in a far more compact way than metre-long
split logs. If you split the wood yourself, buying round
logs will give you up to 15% more wood per stere.
In practice, deviations on the order of +/-10%
compared with theoretical values are to be expected.
Up to 20% is possible in extreme cases, not only
because the wood is particularly straight or crooked
but also because the density of the wood mass itself
can vary.
Incidentally, if you order a stere of ready-to-burn beech
firewood as 50 cm split logs from your wood dealer, the
dealer is entitled under current law to supply 0.85 m³ of
half-metre split logs cut from 1 m³ of metre-length split
logs. To avoid any unpleasant surprises, when
ordering ask how your dealer measures a stere (if the
price is good, you may find 0.85 m³ acceptable).
Estimating your wood requirements
Each kilowatt of heat output requires 0.9 steres of half-
metre split beech logs, or 1.3 steres of split spruce per
year.
In other words, 8 steres of half-metre split spruce logs
or 5.5 steres of beech will replace 1000 litres of
heating oil.
Energy content of one stere of wood in kilowatt hours
Round
logs
fresh-cut
1 m
Round
logs
dry
1 m
Split
logs
fresh-cut
1 m
Split
logs
dry
1 m
Split
logs
fresh-cut
50 cm
Split
logs
dry
50 cm
Split
logs
fresh-cut
33 cm
Split
logs
dry
33 cm
Moisture content
30-60%
15%
30-60%
15%
30-60%
15%
30-60%
15%
Softwood
1 stere contains 0.65 m³
1 stere contains 0.56
m³
1 stere contains 0.62
m³
1 stere contains 0.64
m³
Fir
1205
1269
1038
1093
1149
1210
1186
1249
Spruce
1299
1373
1119
1183
1239
1310
1279
1352
Douglas fir
1402
1478
1208
1274
1337
1410
1380
1455
Pine
1542
1625
1329
1400
1471
1550
1519
1600
Larch
1573
1656
1355
1427
1501
1580
1549
1631
Hardwood
1 stere contains 0.59 m³
1 stere contains 0.50
m³
1 stere contains 0.59
m³
1 stere contains 0.62
m³
Poplar
958
1020
812
864
958
1020
1007
1072
Willow
1107
1200
938
1017
1107
1200
1163
1261
Alder
1191
1270
1009
1076
1191
1270
1252
1335
Maple
1472
1550
1247
1314
1472
1550
1547
1629
Birch
1475
1570
1250
1331
1475
1570
1550
1650
Ash
1658
1760
1405
1492
1658
1760
1742
1849
Oak
1664
1760
1410
1492
1664
1760
1749
1849
Copper beech
1655
1800
1403
1525
1655
1800
1739
1892
Hornbeam
1743
1920
1477
1627
1743
1920
1832
2018
Black locust
1743
1920
1477
1627
1743
1920
1832
2018
Summary of Contents for TWIN 20 kW
Page 1: ...2016 04 02 EN 0000000302 V 001 X 36 0 2303 93412 001 TWIN pellet burner 20 26 kW Operation ...
Page 39: ...ETAtouch controller TWIN function block 39 ...
Page 49: ...ETAtouch controller Buffer function block 49 ...
Page 53: ...ETAtouch controller Hot water tank function block 53 ...
Page 57: ...ETAtouch controller Fresh water module function block 57 ...
Page 81: ......
Page 82: ...www eta co at ...
Page 83: ......
Page 84: ...www eta co at ...