The methanol Ethanol Mix theory is out of my area, but I can investigate later. I only use methanol. I would think the bottom of the lake would be deep and remain close to 50 degrees in the winter. So why your loop is not transferring heat makes no sense unless the loop is at a higher elevation in the lake closer to the surface, which means it has floated up from the bottom to where temperatures are closer to 32 degrees. In the summer you can check the depth, unless the lake freezes to allow walking on it safely. Then you could take a look at where the loops are to see if they are close to the surface. All it would take would be to lose a weight or two and up it would float. Looks like the Unit has the right specs just no place to pick up heat from, plus the theorized potential for the loop flow to drop due to slush forming in the loop. My Carrier is set up to shut down at 20 degrees in the loop outlet water, when antifreeze is used.