Do I need to use a jumper when connecting C2® in the HI 215IT summing junction box?

There is no "jumper" associated with C2®. The wiring associated with the C2® load sensor is as follows:

Gray wire goes to +C2
Violet wire goes to -C2

You can find technical documentation on our website at www.hardysolutions.com. Go to products and select the model you desire, select the Docs and Programs menus for the technical documentation you need.

You do need to use a jumper on the back of the controller if you do not use sense wires between the controller and the summing box.  The use of jumpers instead the Sense wires can effect the accuracy of your C2 calibration.  Please see associated answers concerning the sense jumpers.