I'm building a new house this summer with open-loop geothermal.  I was previously reluctant to do open-loop because of scaling/mineral build-up which can reduce the life of the heat pump.  I was told there is something called a "plate and frame exchanger" which is added in front of the heat pump that solves the scaling problem.  My understanding is that any scaling is captured by this unit.  Does anyone know more about this, and whether it is a good idea?  What is the cost?  Thanks.