High sun, low sun, wind, no wind, big difference

Back during the shortest days of the heating season, Dec-Mid Jan, we had some cloudy, windy days and highs barely in the teens, and 5-15 below at night, windy all night. During that time I had to keep the GARN temp at 160 during the day and 180+ at night. At this moment I'm staying comfortable with 130 water and it's 9 below zero. BUT, the Feb sun is just clearing the pine tops and no wind. When I build a fire this afternoon it will have been 18 hours since last burn.
So I think I'm further ahead by having designed my system based on previous oil usage, than I would have been trying to do a heat loss calc based on the coldest day like all the pros recommended. It just seems like, after five years of using my Garn, that there are things to consider that the math/formulas don't account for. Does that make sense?

maple1 said:

When you say designed your system, do you mean the entire distribution system also? Or just the heat making (boiler side) part of it?

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Boiler side.

bpirger said:

Well, of course you could account for the solar gain, wind/drafts, and really low temps and then it would all be "exactly" like theory. But that takes quite a lot of effort to model so well! But I agree, there's room for everything. You had to keep loading that Garn presumably during the cold, windy days/nights....so it was the extreme (hopefully!) side of the heat load. The Garn can crank out an enormous amount of heat....and the great thing is when it isn't needed, it can be used later.

Did you keep the fire burning essentially "continuously" during those coldest times? I suspect that was never in the plan during the design time.....was it?

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Hell no. Never have come close to continuous burn. The drawdown range would only be higher or more narrow during coldest/cloudy/windy times. I would crank it up to 180+ in the evening and it would be like 145 or so in 12 hours with the heat turned down at night. One fire would bring it up to 160 or so and I can coast for 6-8 hours on that during daylight hours. Two evening burns and I'm back up to 180-190 again. So 4 burns in 24 hrs.
With the same outside temps but full sun and no wind 2 or 3 ( depending on the wood) burns will work because I can draw down to like 130 or less during the day. With highs in the 30's sunny, no wind and lows in the 20's a couple burns a day will do fine because I can work it down to like 110-120 during the day and one burn, because of the higher difference in temps, will boost it up to 160 or so and that's enough to go through the night. If I burned that thing continuously it would be boiling all the time.