Low consistency refining (LC) as a second refining stage, after a HC-defibration is an energy-efficient process solution. This HC-LC concept has for some time been explored in pilot scale and shown promising results. However it is clear that in order to obtain an optimal development of pulp properties the LC-refining has to be optimized with regard to process conditions. In this study the effects of temperature, pH, and specific edge load in the LC-refining on the pulp quality were investigated. For this purpose a mobile LC refiner rig placed after a primary stage HC mill refiner in the Braviken Paper mill, Holmen Paper was used. The trials show that energy savings are possible with preserved properties in the production of mechanical pulp. High temperature, high pH and low specific edge load were indicated to be preferable for both the tensile index development and for preserving the fibre length of the pulp. An increased degree of refining developed as expected the tensile index but too high specific energy resulted in some fibre shortening.