We try to mount them on the northern side of the building to ensure it received the least amount of direct sunlight as the sun will add quite a few degrees to the actual temperature.

We actually use the C2N-RTHS sensors over the CHV-RSS sensors as you can connect the C2N readings to multiple thermostats easier, plus you get the humidity reading as well. We install them into the bottom of a 6x6 PVC box with conduit running back to the rack area to ensure we can replace/add a wire later on if need be.