Many of you are familiar with this website but I wanted to offer it again for those who have just joined or have recently become interested in wood boiler/ pressurized storage systems. It's in Swedish but a picture is worth a thousand dictionaries."Ute" is the outdoor temperature. "Kontor" is the office temp. http://www.elstyrteknik.se/pannrum/ This is a pressurized storage tank directly coupled to a wood boiler with return temp protection via what is apparently some sort of thermostatic (Danfoss or Termovar) valve. The heat is taken from the tank for what I assume is radiant heat emitters (very low delta T) in the office. The boiler just heats the tank independently from the load. A mix valve dials down the temp to what ever the heat load requires. By watching the schematic and checking in several times a day you can see how simple this sort of highly stratified storage can be. The boiler fires up and fills the tank from the top and the heat is then drawn back out from the top through a seperate tapping so the boiler can be filling the tank at the same time hot water is being drawn out for the heat loads. This schematic is not as detailed as a line graph nor is it any help over time because it is only displaying what is happening right now. But it is easier to 'see' the basic BTU flow than a line graph. For those not yet convinced that stratification is all that important in a storage tank, tracking this display over a few days will help make the issue clearer.