So on with the story. Details of constructing the six loop, 4200 foot horizontal loop field for this project were previously posted in the appropriate ‘loop field’ section of this forum (‘My most awesome horizontal closed loop’) The two inch header lines from the loop field were crossed over to 1 1/4 inch copper in the crawl space. Very standard using off the shelf materials. Next the HVAC contractor started the flow center and heat pump piping in 1 1/4 copper according to design specifications. The flow center is non pressurized using a Grundfos Magna Geo 32-140 variable speed in series with a fixed speed Grundfos 26-99. Control of the two pumps is accomplished with either a flowmeter or with differential temperature sensors across the heat pump supply and return. A manual flow center current mode is also available. The Grundfos flowmeter looks like a potential weak link with rather substantial head loss so I went ahead and added a flowmeter by pass. Reinforced steel flex hoses are used liberally throughout to dampen vibration as are brass unions to facilitate maintenance or replacement. Sensor points have been added to both the supply and load loops to allow continuous system monitoring and data logging: Loop supply temperature Loop return temperature Delta Pressure across the heat pump supply (GPM flow rate) Load supply temperature Load return temperature Delta Pressure across the heat pump load (GPM flow rate) Current meter to the heat pump Current meter to electric resistance heater in DHW tank Eventually all this will tie in to a main distribution panel downstream of the heat pump either directly or via the buffer tanks. For the main distribution panel I went with Eagle Mountain who build a customized distribution panel that is plug and play including the control systems. They do nice work. Distribution panel pumps have the following assignments: Pump 1 - Domestic hot water with priority override Pump 2 - Main water to air handler (cooling or heat mode) Pump 3 - Tower water to air handler (cooling or heat mode) Pump 4 - Manifold 1 in floor heat (all in floor heat is 1/2 inch hePex embedded in 1 1/2 gypcrete) Pump 5 - Manifold 2 in floor heat Pump 6 - Manifold 3,4,5 in floor heat Pump 7 - Garage floor cement slab. The in floor loops have all been pressure tested / filled and flushed with pure water. The hePex piping runs from the in floor manifolds to the main distribution panel. Just a look at one of the five in floor manifolds scattered throughout the residence providing a ‘highly zoned’ in floor heat experience. Manifold control is via thermostat with floor slab sensors. Over the next two weeks plan on fill and flush the loop field using a flush cart, hooking up the heat pump itself and installing the buffer tanks.