I have a couple of problems with my Geo system that may work out to have the same solution. First I have a strange problem with the domestic hot water desupeheater system on my Heat Controller ( Comfort-Aire) heat pump. It is a model HWW060B1C01CFC. This is a five ton unit for a smallish house of approx 1500 sq ft on two floors with most of the house over a crawl space except for a small basement where the heat pump is located. The closed loop slinky system running 25% methanol has about 500 ft of length. The pump was certified to be running optimally by the contractor and Heat Controller when the operational specs were sent for review. The load side is retrofitted tubing under the joists with bubble insulation and regular fiberglass over that. The load side is running straight water (softened) only. The heat pump is equipped with a domestic hot water desuperheater system. The system is plumbed upstream of the electric hot water heater as shown in the attached diagram. The problem is that the water is getting insanely hot in the line to the secondary tank from the heat pump. In fact it boils. You can hear it in the lines on cold nights especially. The standard pipe insulation which is rated to about 80 C has melted completely off the pipes on the lines the outlet line from the HP. The contractor is not having much luck troubleshooting the problem with Heat Controller techs. We believe the recirc pump is working. The question is why is this water getting so hot if it is circulating as it should? This leads to the second problem which is that the system is not able to hold the house at the thermostat setpoints on cold nights like we had recently. For example the outside temp was -12F and the setpoint was at 69F but the main floor zone was only at 66. I completely realize there is a whole huge bunch of other factors that could be causing the house not to reach temp. The point though is it would probably do better if we could dump a little more heat into the radiant load side. Which brings us to the overheating hot water system. If there is that much heat to spare on the desuperheater side could I use some of that heat by plumbing it through the buffer tank with a plate exchanger? I realize that the extra desuperheater heat my be a symptom of the fact that we are not getting enough heat exchange with the house itself. That is another very long complicated problem but could I solve both problems with the plate exchanger? Or is the desuperheater overheating a separate problem that needs to be resolved? Thanks for all help you can give!