This paper proposes an effective method of variation of speed in the recirculation pump and consequently ensure optimum range of flow for absorption chillers when it uses the pair LiBr/H2O. These systems operate at subatmospheric pressures, merely for this reason the use of non-invasive flow measurement methods. The need for low power recirculation systems in such devices makes it impossible to adopt three-phase loads on the driven of the pumps. These implications prevented the achievement of advances in these systems, limiting the success of important contributions in the literature. Due this, it was designed an experimental apparatus reproducing the flow conditions which are submitted to absorption chillers with LiBr and developed a device that could changing the low power load speeds. It was implemented in LabVIEW language, a PID controller action system, which allowed tested to the flow control, initially for water and then to the saline LiBr/H2O.