Why is it important for GFX to feed both the water heater and plumbing fixtures?
The answer to this question is far from obvious, which is why U.S. Patent 4,619,311 was granted. Perhaps the easiest way to understand this is to consider an ideal example of 105F shower-water comprised of an equal mix of 155F and 55F water, and experiencing no air-cooling before entering a perfect contra-flow heat exchanger at 105F . Three cases are important: The Obvious Case — passing just the cold water feeding the water heater through the heat exchanger, where it’s preheated by 50F to 105F as the 105F wastewater is cooled by just 25F because there is twice as much of it. This case corresponds to recycling 50% of the heat traveling down the drain. (In practice, the Model G3-60 will cool the wastewater by about 20F at 2.25 gpm while recycling about 40% of the waste heat. Lowering the water heater set-point will decrease the flow-imbalance and increase the efficiency.) The Equal-Flow Case — passing water feeding both the water heater and cold side of the shower through the heat exc
