KingCoal wrote:here's a couple examples of what I mean.
early in Oct. I used 12#'s of coal thru a day that was reported to have 16 HDD. that's .75 #'s per HDD in those conditions, or .5 #'s per hour
this month I used 72#'s during a day reported to have 64 HDD. that's 1.125 #'s per HDD in those conditions, or 3 #'s per hour.
steve
I can see where that would happen. I now believe that daily is going to show such deviations, and that your consumption vs. HDD results should be statistically "smoothed" over 3 HDD (3 day) periods, due to variations including your feeding times vs. the times when the weather services compute their daily highs and lows (midnight to midnight most likely), from which they derive their daily HD's.
I feed my boiler most typically every 3 days (every 2 days only when its really cold outside), so I naturally benefit from such HDD data vs. consumption "smoothing", and I do not see the more radical daily deviations (which tend to smooth out and disappear over time).
I mentioned in a previous post to a different thread that over 3 day feeding periods I'm generally within 90% vs. forecast (projected) via HDD's, and over a month I'm generally within (or at better than) 95% precision. If I'm only in agreement to about 90% over any given 3 days, I can see where I might be only good to about 75-80% if I monitored this daily.
I also have the distinct advantage of tight thermostatic control of room temperatures, which a hand fired stove will never have. This will mean that for a hand fired stove the deviations will naturally be larger vs. HDD's (and perhaps much larger), since this level of room to room temperature control is not possible for a hand fired stove. The ability to tightly control the room temperatures over 4 distinct zones of the home makes consumption vs. HDD's far more linear.