Gmoccapy tool setter block height overrides G54 zero

Hi I use freecad to generate the g-code to linuxcnc. The cnc homes and tool setter works my question is when i set block height to the top of my work piece the tool offset works what happing now is if I try to zero g54 to a work piece the z zero gets overwriten by the block height.I thought the block height was for initial setting of tool setter. The gcode file ask for tool M6 T7 G43 H7  at the start . What Iam I doing wrong how would I change this to tool offset is from work piece ?