Just for comparison, my garn 1900 holds 1906 gal x 8.43lbs/gal of water=15,896btu/deg raised, per my hundreds of weighed wood burns it averages out to approx 3lbs wood per degree of storage raised. Quick figuring about 1.5 lbs per degree should get you in the ball park for the jr., for 40deg raised= 60lbs wood. I don't know what the jr will hold and 2 how much wood will burn smoothly at a load. This depends on your your wood type and moisture content, dryer smaller splits=smaller load, higher mc and larger splits=larger load will burn smoothly. I have found with the firebox size of mine, same size as a 2000 that I can fit 150 lbs wood, 135lbs if large split is really pushing it, the comfortable spot is between 80/110 lbs wood load. My thought would be to load about 75lbs to start and reload 45 about 1.5 hrs later to charge your 2000 gal 40 deg, and clean the ash out of the firebox with one swipe of a flat shovel before the next firing.
As kwmeh09 states and jebatty will confirm that this can't effectively be operated as a downdrafter with day long occasional loading to keep the fire going for a extended time. In extreme conditions you can add a firing in between you normal schedule.
Id call dectra about how much of a wood load the jr is confortable with and their thoughts on combining with your onsite storage.
On the other hand being a big decision, you really should look at the 02 controlled froling.
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