I've been asked a few times from other members if its saving coal, the answer is no, but its saving in other ways that more than make up for the 2 more tons that I burn..Now that I've ran the Axe for a couple years and can quantify DHW usage we can look at some comparisons..
Overall statistics of the over modified Clayton handfed furnace.
Usage - averaged 5.5 tons per season.
Duration - 6 months per season, otherwise used wood pellets and electric heat for 2 months
Heat load - 2400 sq ft to 73 degrees, automatic thermostat controlled combustion, convection blowers ran 98% of full time for the house
DHW - variable, passive heating only with natural convection thru coil, electric tank finished heating..
Maintenance - average tending 1 time per day, somewhat labor intensive and required 30 minutes start to finish
Overall statistics of the Axe
Usage - averages 7.5 tons per season
Duration - 8 months per season
Heat load - 2400 sq ft to 73 degrees plus 500 sq ft outbuilding heated occasionally to 68 degrees otherwise kept at 40 degrees, thermostat controlled heating, convection blower runs ~30% of full time for the house
DHW - 100% heated for 8 months, coal usage for DHW estimated at about .75 tons
Maintenance - average tending 1 time per day to observe its running, pull some coal over the feed tube end, check ash tubs, occasionally oil moving parts, labor wise easy and takes a max of a few minutes..
