Hi All, I operate a small Textile mill at my farm. We process raw animal fiber into yarn and other products. A big part of what we do is wash raw wool. We use water that is 160*. This temperature is the most efficient for getting the lanolin away from the fiber. Other fibers are washed at lower temps (120 to 140*) Currently I am using a Takagi T-M32 which is 240,000 btu. In the winter my ground water is between 50 and 54*. We go through about 500 gallons of heated water per 8 hour shift. We need as much as 110* of temperature rise(which, in my opinion, is a lot) At these temperatures, understandably, I can get about 3 gpm of 160* hot water out of the T-M32. I'd like to raise that to 4 or 5. I have about 10 gpm available (before heating). I have purchased an additional heater, a Takagi AT-h3-DV-p (the T-M32's have been discontinued) it is rated at 199,000 btu. I use a dedicated propane tank for fuel so I will have enough gas to provide fuel to both units. My question is (after that long winded intro), for my application, should I run the units in parallel as master and slave units, or in series, with the first one set to preheat to 110* and the other set to heat to 160* ? Thanks in advance for any info you might be able to share.