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I have been updating my baseboard heated house to an all radiant on top of floor sandwich. I have a standard cast iron boiler (which is about 3 X to big) with a Taco 5000 series mixing valve (no outdoor reset). Over the last few years, I have been adjusting my boiler/radiant settings to get the boiler to fire as little as possible (it only takes the boiler 3 minutes to bring the water up to temp with a 10 delta). What I found last year, was that I got the boiler to fire the least amount of time and cycles by using 100% constant circulation along with a control I built to increase the boilers delta (it also gave the house the best comfort around 70 F). I had to manually adjust my mix temp based on the outside temps. My mix temps are 100 F when it is 20 F outside, 110 F when it is 10 F outside ect. This could be automatically adjusted with outdoor reset on the mixing valve. The one issue I was having with the larger delta on the boiler is that the mix temps would vary as the supply water changed from 180 to 140. Is there a mixing valve that would have outdoor reset but also maintain a constant mix temp with the changing supply temp?