Hi All, I've been spending recent days installing my WEL (http://www.welserver.com/WEL0899/) and analyzing some data. During that, I wanted to also compute the heat of extraction. I was hoping you could confirm my math: Delta T = 7 deg F Pressure drop = 2 psi Flow (according to attached manufacturer's table) = approx. 8 gpm I'm running glycol at an assumed 25%. 8 gpm X 7 deg delta T X 485 = 27160 BTU/hr Given that I've got a 4 ton Tranquility 27, the HOE number is low, correct? So I thought about the possible causes. One thing that caught my attention is that my QT flow center has a single Grundfos UPS 26-99F/3 pump. The manufacturer's (B&D) instructions say this unit is good for up to 3.5 tons. Over that the two-pump version is needed. How important is this? Also, the Grundfos pump has 3 selectable speeds. Will changing the speed have any impact on either my GPM (seems obvious it will) or my delta T? From reading on this forum, it seems that my GPM should be 12. 3 gpm per ton is what's prescribed in the Tranquility manual. However, 12 gpm is at the extreme high end of the table I attached. It also seems my delta T should be lower (lots of folks are at around 2 deg F). Your thoughts are appreciated. PS - WEL setup is still rough. Looking for some free time to improve on it.