lsayre wrote:I went through 1,130 lbs. in November, and 1,492 lbs. in December, so it appears we are burning at somewhat similar overall rates. Since October 14th I've used 3,312 lbs. of anthracite.
Have you noticed (as I have) that your December efficiency was much better than your November efficiency, and leagues better than your October efficiency? I burned a bit more than 38 lbs. per day in October, a bit less than 38 lbs. per day in November, and a tad over 48 lbs. per day in December.
Are you also heating all of your homes hot water with coal, and did you factor this into your anticipated usage calculations? If you are heating the homes water with coal you are probably using about 5 lbs. per day of coal on average to provide for your homes hot water. About 1,000 lbs. of coal for the heating season should be fair guess for your DHW demand.
Allowing for various factors such as coals inherent water content and a boilers nominal efficiency, I believe its best to assume that in the end you should realize quite close to 10,000 BTU's of actual output from each pound of coal that you add to your boiler. If you used 600 gallons of oil for home heating only, and your oil furnace is 85% efficient. then putting it all together I get:
600 gal. x 138,600 BTU's/gal. x 85% eff. = 70,686,000 BTU's
70,686,000 BTU's/ 10,000 BTU's per lb. of coal = ~7,069 lbs (3.5 tons) of coal required for heat only
Add to this roughly 1,000 lbs. of coal required for hot water and you should have a projected need for a tad more than 4 tons of coal for the season.
Well, at least my math isn't off! Your calculations are what I came up with. My old oil boiler was 84% on a good day. I used the old boiler's tankless coil for DHW last year so the load shoould be the same. When I installed the LL110, I added a storage tank to its tankless. I think a nice Weil McLain indirect may be in my future, and Ill use the storage tank as a summer dump zone....
However, the way my DHW works, it never calls in the low limit to satisfy recovery?