Just brought a new 325G online. First brought the in law apt (where we live) online 2 weeks ago
then the main house (where son & wife live) on last week. A question on another NC thread about
how often a 400G is loaded inspired this posting.
My brother questioned how much wood we're burning. He claims his buddy only adds about 6
pieces of wood twice a day to his CB boiler to heat his 3000 sq ft home with DHW. I visited the
fellow last summer. He buys unseasoned wood in the fall for the winter so I suspect the story
is not quite complete.
So I did some calculations and would appreciate any feedback. Here they are:
One cord of seasoned red oak: 24.6 million btu/cord
2000 sq ft home, 8' ceilings: 60000 to 80000 btu/hr (using 30 to 40 btu/sq ft)
DHW 30000 - 50000 btu/hr (estimates reviewing several heating sites for sizing hot water heat)
therefore consumption should range from a low of 2.16 million btu/day to 3.12 million btu/day
net consumption would be a high of 11.4 days/cord to low of 7.9 days/cord
We are heating more than double the example as we also heat a 1000 sq ft basement
and a 900 sq ft garage though these would have much smaller heat differentials.
We are seeing not surprisingly about 4 to 5 days/cord
Some known errors:
Boilers are probably 75-80% efficient so consumption would be higher
DHW shouldn't be 24 hr/day so consumption should be lower
btu/hr numbers are based on heating to 70 degrees in 20 degree weather
we've seen single digit nights recently so consumption will be higher
Our loading experience using mostly oak split 18 - 21" originally for inside wood burners
tossing into boiler results in loosely full load, next wood will be cut longer and split less
a single digit night will burn a loose full load in 6-7 hrs
20 degree night with 30 degree day can be loaded just once in morning and once in
the evening.
Any thoughts