benz k6 wrote: I'm really interested in how to determine heat load
Rob's reference to "heat load" is interesting, because it combines 2 different methods you may see discussed on the forum. Some advocate reliance on "heat loss" computations, wherein a computer program takes info from you, applies some hidden assumptions and presents you with the number of BTU's per hour of "heat loss" you need to be able to replace. As long as you never open a door or window, use a setback thermostat, experience weather conditions more severe than the program assumed, etc., you might do ok with that. You may note, however, that the advocates of this method generally have lots of recommendations on how to shut off different parts of your system when it can't get the radiators hot in real-world conditions. Personally, I don't find that very comforting.
The second method is to inventory all of the radiation you have, and determine how many BTU's it is designed to provide. Like in the shop you would say 2 x 45k = 90k btu/hr. If those things are going to run, you better feed them the 90k, or they're going to be blowing around cold air. Add to this "attached radiation load" a reasonable allowance for losses from the distribution system, commonly called a "pickup factor". Install a boiler big enough to supply all of that, with maybe a little extra as a margin for error. This is an "old school" method used by people who actually expect their systems to work properly after dropping a bunch of $ into purchase and installation.
So the choice is yours. You can size the boiler to power the radiation you are trying to run, or size it according to the hidden assumptions buried in some computer program. Hey, you may save a few bucks if the computer tells you you're ok with a little boiler, and if the computer was wrong you can always keep yourself warm with the output from its cooling fan.
Mike
P.S. If the underground pipes from the outbuilding to the house can't carry all of the BTU's associated with the radiant flooring, pickup factor and DHW use in the house, the boiler need only be sized based on the btu-moving capacity of the pipes.
VERY GOOD ,very sensible explanation. How many times during this winter & last winter have I read of boilers that just couldn't keep up,because they were undersized for the work load. I may have missed the threads on the boilers that were too big,i just do not remember seeing any complaints on having a boiler oversized. ~~~~ benz k6,WELCOME to the coal forum. From an OWB to a coal boiler,you are heading the right direction with heating fuel choice,just last yr at this time I was feeding a wood monster too. Winter is much easier to deal with since heating with coal.
