Hold the heat exchanger where you want to mount it then outline it with the pencil on the wall or floor behind the exchanger. Set the heat exchanger aside while you install the initial brackets.
Screw the Z brackets to the wall just below where the heat exchanger will hang using the screws. The brackets need to be mounted into studs in order to support the weight of the heat exchanger.
Screw in the end of the two spanner straps so that they are evenly spaced along one side of the heat exchange outline.
Place the heat exchanger back in place, sitting on the Z brackets, then pull the spanner straps across the front of the heat exchanger and screw them to the stud. The straps will prevent the heat exchanger from falling forward while the brackets will keep it up, in place.
Attach the tubing to the heat exchanger. Typically the tubing will be copper with a screw type connector at the end which screws onto the input or output of the heat exchanger. Make sure you connect the recirculation tubing in a closed loop, rather than going in the input on one side and attempting to leave the output on the other side of the heat exchanger.