I've just had a new 2 and 1/2 ton Rheem Heatpump, model RPNL, with RHLL air handler installed in my attic using existing ductwork to replace a 24 year old Weathertron of same tonnage. When I asked the installers about the static pressure, they informed me that they never do this, don't know how. According to the info I have read, the x-13 GE blower motor should be set to switch 2 or 3 depending on the static pressure. I figured that it's better to assume I have a lot and connect to switch 3 to insure maximum airflow over the coils, so I had them set it on this switch. What negative effect (other than wasting electricity to turn the motor) will it have on my system if I have lower static pressure and am pushing too much air across the coils? Also, is there any way to ballpark figure static pressures based on duct size, configuration and materials?