EnergyManager wrote:350 EFM Coal Stoker
Still the best size unit ever made by EFM for a modern house.
90,000 BTU is more than most people need especially if zoned.
A 350 produces alot more then 90k btu even the orignal ones with the small pot & S-15 stoker had a max of 6 teeth feed rate 2.5lbs per hr per tooth with rice coal 15 lb max feed rate per hr 15 lbs x 13.500 btu per lb = 202.500 btu's subtract
15% or 20% for heat loss depending on set up 172.125 btu's to 162.000 but's max out put . Now stick a S-20 stoker & pot
your at the 520 #s max feed 8 teeth 20 lbs per hr max with Rice coal with buck it is 16 lbs per hr max feed .
20 lbs per hr x 13.500 btu per lb = 270.000 btu's subtract 15 to 20% for heat loss 229.500 btu's max to 216.000 btu's
Remember these # are for the older 520 -s-20 which olny had a 8 teeth feed rate max The newer s-20 with the longer gear arm and with the bigger pot has a feed rate max of ten teeth 2.5 lbs per hr 25lbs per hr max rate . 337.500 btu's subtract 15 to 20 % heat loss 286.875 btu's to 270.000 btu's max out put using coal at 13.500 btu per lb the numbers will be higher or lower depending on the coal being used. Even at 4 teeth with a 350 the out put would 108.000 btu to 114.745 btu's
3 teeth feed rate is from 86.625 btu's to 81.000 btu's . Agreed the 350 is capable for most of the newer homes aswell as alot of the older ones being that is what has been heating them more often then 520's most people think they have a 520 when it ends up being a 350 in the basement that's been heating the house for decades.