Rob R. wrote:If you have a steam system, that changes everything. You have to ensure the coal boiler is large enough for the amount of radiators you have.
I'd like to basically agree with Rob, but hijack his post for a second to refer you to a recent discussion of coal-fired steam boiler sizing on another thread - see where to buy a 300,000 BTU coal fired steam boiler stoker
"I see people measuring their installed radiation, adding a small pick-up factor and then deciding what boiler to buy based on the ratings on the manufacturer websites. I agree with you that many of those ratings are higher than the unit is actually likely to perform, and that's part of why I'd be more comfortable with specifying more excess capacity. I've seen all kind of weird stuff happen when stokers of different designs get pushed close to their maximum output. For example, I had a flat plate stoker that picked a deep cold spell to let me know my recent coal delivery was more prone to clinker formation - due to plowing, etc., I had to baby it when I needed it to really go. Likewise, even EFM's can come up short at the top end if your coal has too large of a % of undersized pieces, but you may not find that out until you need that output. Making steam by coal, I'm much more comfortable building in excess capacity to provide protection against such factors, not to mention the boiler needs cleaning/DHW needs/future expansion/etc. factors that might lead you want to keep some capacity in reserve. And I know I'm repeating myself, but I believe I'd get the same heat with less coal using a bigger boiler running at 2/3 of its capacity vs. a smaller boiler running flat out (at least if the bigger boiler has a bigger heat exchanger)."