normally measured

SPF1 is normally measured on the brine/water sides of the evaporator/condenser, but it could also be measured directly in the refrigeration loop with e.g. the Climacheck equipment [10]. This requires measurement of the pressure and temperature of the refrigerant. This methodology is very efficient if the status/condition or diagnosis of the heat pump is to be evaluated, but generally in domestic heat pumps, the measurement  is not easy to carry out since measurement sockets are not generally installed