Question: Thinking about adding a coal boiler to my existing multi zone hot water heating system. System is set up with six zones, five of the zones do various locations in the house and the sixth zone does domestic hot water by-way of indirect water tank. Sized the boiler to be 80 to 100k btu with a gas boiler currently sized at 70k btu @ 87% efficiency. Question#1- Is there a boiler that is a stoker that will modulate to the load of the system and will burn rice coal. Have looked at the Keystoker but the problem is for my locality is to find buckwheat coal economically. Question#2- Can I use this system during the summer to produce hot water. Chimney is interior to the house and drafts great all year. Current boiler vents out the sidewall. Question#3- Looked at Hormones SF-160 wood/coal boiler. Can I use this boiler year round? Both the dealers in my area could get me the boiler but could not answer my questions about adaptation to my system. What is the minimum heat produced by the boiler that I would have to use the over heat zone for. Maybe one zone is not enough to dissipate heat during off cycle. Can I build smaller fires to match the expected load. What is the firebox reducer option for and how much does it reduce capacity. Answer: #1 Because of the low price of oil, these boilers have fallen out of fancy. A company called EFM in Emanus, PA used to make one..and perhaps they still do. Try them. Electric Furnace Man Division of General Machine Corporation 302 South Fourth Street Emmaus, PA 18049-3891 Phone: (610) 965-9041 Fax: (610) 967-6593 #2 You can use it all year. I think it needs a regular class-a chimney, but check their specs. #3 Does not sound like you want a hand-fired unit. It would not be realistic to use such a boiler year-round.