20 Sqft Mat, Electric Radiant Floor Heat Heating System with Aube Digital Floor Sensing Thermostat Carefully calculate the square footage of the area to be heated.  Do not include permanent objects or areas that are not walked on.  Purchase the corresponding heating system size. Simply unroll the floor heating mat with the cold lead running up the wall to the electrical box. The adhesive tape on either side of the mat allows the mat to stay in place and lay flat.  You can manipulate the mat to fit the desired heating area by using the turning techniques shown below. Install the mortar and tile over the top of the heating system. Connect the floor heating thermostat. AF mode-controls ambient temperature with floor temperature limitation A mode controls the ambient air temperature F mode controls the floor temperature using an external temperature sensor Two temperature sensors-one in floor, one in thermostat for accuracy and security Red light and alarm indicates lead wires have come loose from the terminals or damage has occurred to the heating system A white light indicates the monitor is operating Can monitor up to 3 systems at one time when they are temporarily connected in series