I am confused about delta t when charging storage tank

[jebatty]

You may find that, if you bring your boiler up to a higher temperature before the circulator starts, your boiler will operate better and maintain a higher temperature supply. The extra heat from hotter water around the firebox likely will enhance production of wood gas.

 

[mwk1000]

I let the danfoss choke of the cold water feed and keep the boiler starting at 140. I may try je's thought and raise the temps to 160 because of the high dose of cold I have when charging the tank but so far this setup has been the best conpromise in all the factors discussed. I also like to time the burn so that I haven't enough energy left in the wood to drive the boiler to idle. I have seen that the diffrence between the eko sensor and the true boiler feed temps make it even harder to get good transfer when the tank temps are high. The boiler idles at 195 but the actual temp leaving the boiler is 185 it reaches the HX say 183 is my max operating real temp.

I used to set the tank circulator on low speed 15-58 3 speed model but as JA mentioned I use a higher flow rate now to do better in the later stages. I do miss seeing 30-40 degree delta's into the tank but I am actually moving more btus this way.

I have a chart of the two delta T's source/boiler and load/tank that I use like religion to see if it is all operating "normally". It took me a long time to understand the quirks, and like many time in the past what I thought was NOT what was happening. Would not be suprised to find I still don't know what I'm looking at.

You can "see" the danfoss at startup is restricting flow to the HX creating the huge startup source delta T. As it opens it starts to drop , as does the wood energy later both contribute to the slide look of the chart. ( The spikes in the load line are actually when a furnace kicked on. or at the tail end when the controller is cycling every 5 min squeezing out whatever is left.)

You can also see when the tank pump starts early on and drops the delta T of the tank( black) right down. The one thing that has struck me the most it the fact that "steady state" does not really exist , at least for how I intend to use it. From the wood fuel input , to the HX changes. I did want to change out my tank load pump for a true variable spped so that I could use the controller to dynamically change the flow rates raising the rate as Delta T decreases -- but I'm to cheap to buy the variable speed when this works. But it would be fun to add that logic into the controller because it is new for me.