The biggest problem In my case is my baseboard, with 180 out to baseboard it will return at like 165, so unless I used some system to return the water to different levels in the tank it’s gonna mix anyway. Radiant would be soooo much better.
I suppose essentially what you need to do is charge the tank to about 165F at bottom of tank. My tank is horizontal, not that that necessarily makes any difference, but when my bottom of tank is 165 and charging is continuing, bottom of tank temp is rising rapidly, which means that the water column above quickly becomes much hotter. I don't have mid tank sensors (could be done, though), but I suspect that in this situation about 190F water sits in at least the top 2/3 or more of the tank. Returning 165 water to the bottom of the tank might not be giving up many btus. But as you say, radiant would be much better.
My argument for that is if you charged the tank with the highest temp water you can without idling the boiler, when the bottom tank temp rises sharply as on page 5 of the referenced pdf, the tank is charged.
This is the point I'm making above.
I would have to agree that you should be able to control your stack temp with water flow ...
I think this is somewhat problematical, and is highly related to the engineering design of the boiler and the firetubes. I have 8 tubes, 3" diameter, and x" long. The velocity of the flue draft will determine how long and how hot the hot gases are in the firetubes. Controlling the draft, faster or slower, seems to be the primary way to control the ability to extract heat from the firetubes in a typical home boiler. How much heat is extracted by the surrounding water/water flow will depend on the interior design of the boiler water jacket and how that water flows through the firetube matrix and mixes as it flows from the bottom return to the top supply. Increasing the speed of that flow does not necessarily equate with the ability to extract more heat in any determinable fashion, except by trial and error with measurement. The flow will take the path of least resistance, which likely is not through the firetube matrix. While some additional heat may be extracted, I suspect it will not be linear with increase in flow. And second, in all cases increasing flow is limited by the capacity of the plumbing, pump head, etc.
Also, for some reason I am convinced that my laddomat cools my tanks as the eko is out of heat, because once again I see lower temps going into the top of the tank(but maybe the flow is just slowing way down?)
A differential controller should largely solve this problem. When return temp is less than ___* less than supply temp, the circ should shut down.
...boiler return water protection...
An interesting side note. I've been involved as a lay adviser in a non-profit institution installing a Garn and a Woodgun for primary heating, to replace heating previously provided by 4 LP staged boilers. The LP boilers will remain to supplement, as needed. Beautiful looking install, but two issues have quickly surfaced and were not dealt with by the HVAC contractor: 1) no return water protection for the Woodgun, and 2) at this point believed to be inadequate specs/design on the HX a) to transfer to the pressurized system all the btus that the Garn can produce and b) to operate in a reverse direction to transfer excess Woodgun btus to the Garn storage to prevent the Woodgun from idling. The HX issue highlights what we know well, and appears not to have been adequately considered or understood by the HVAC contractor: as delta-T closes it takes a lot more capacity to move btus. It will be intriguing to see how this is worked out.
