Thanks Miller'. Great to know. How is your Tarm set up? OK, I MUST get this all in and running by the end of this week, if not sooner. So, I am torn between these two setups. W = domestic hot water F = Oil Boiler H = Water to air heat exchangers. T = Tarm This one... To 'me', being a complete newbe here seems best because my Tarm is preheating everything before in enters my system. Thinking that if needed that my domestic water circulator could act as either a continuous flow or an overheat circulator. (that gray box being the Honeywell) . To me this would be not only keeping the oil boiler hot, but also store hot water in the domestic tank. ??? Then this, suggested and used by Paul..... Sweet easy hookup is a plus here. I would do this for sure, but what concerns me is that the hot water from the Tarm is being cooled when the heat calls for the circulators to be on, by the return water mixing with the hot Tarm water before entering the oil boiler. Would this then not make my oil boiler want to turn on in order to get the temp up? Or is this mixture what I need and still hot enough for the boiler not to call for the burner to start up? As soon as U hear some good answers I will get TO IT! I'm excited to get this up and going! Thanks everyone!