Hello, Before I begin I need to mention that I’m not an engineer or an HVAC contractor, just a general contractor with over fifty years of experience building and renovating homes. I posed this question about seven years ago and had one response and was not convinced that the response was correct. My GSHP systems were installed in March of 2011. Later the following winter my HVAC contractor called me during a cold spell and asked me to check the incoming water temperature on my air handler. I was surprised and concerned that the temperature reading was 49 degrees, about ten degrees below the ambient ground temp in Wake County North Carolina (60 degrees). All of my reading about GSHP systems before installing the system talked about using the constant temperature of the ground to provide a heat sink for heat and A/C.From that, I thought the loops were sized to maintain a near constant ground temperature, retuning the loop water to the heat pump at near the same temperature as it entered it. My thought is that the lower the temperature of the ground the more the system needs to work to produce the same amount of heat and therefore is less efficient (using more electricity) as the ground temp falls. Just like using an air to air system when the outside temperature falls. The responder to my previous post said that it was a question of the law of diminishing returns. That if I did have more loop or pipe length any gain in efficiencies from a higher ground temp would be offset by the additional cost of running the circulating pump for the larger loop. I’m not convinced. With a “warmer” loop it should take less time to produce enough heat to warm the house and therefore less run time for both the compressor and the circulating pump. So, seven years on my questions are: · How much more loop would be required to maintain a near constant ground temperature, say within 4 degrees, at 10 degrees outside temperature? · Can the same size circulating pump be used for the increased loop size? · How much more electricity would be consumed pumping water through the larger loop than the smaller one. Some specifications: I’m using a 3-ton Climate Master 27 horizontal package unit, installed in a “closed crawlspace”. I have two - 290’ deep, 6”, bore holes backfilled with bentonite grout and the bore holes are about 100’ from the house foundation. There is 17’ of overburden at the bore site and the water table is 64” below the surface.