I already have the Tarm. I was just curious how the E-classic is integrated into an existing heating system. For example... what if I had bought an E-Classic instead of the Tarm? Would I have set it up the same? Does it have the same concepts as the Tarm... Like " Primary-Secondary" or "Series" when it comes to setting it up? Or is it a whole different ball game? Don't get me wrong.. I love the Tarm... just pondering the " What if " scenerio. Cost and so forth too. Buying the Tarm, adding a zone with 34 ft of high output baseboard, and having plumber and electrician do all of work came to 11,700 shells. What would have been the price of the E-Classic with plumber and electrician hooking it all up? This would include all costs... ditch, piping etc... and hooking into my current system. Also... does the E-classic use the same idea as using my current oil boiler as my back up?