The parameters that guide equipment selection are uniformity of heat, energy efficiency, ease of control, ruggedness, maintainability, and cost. Where batches-of-one are the norm, then speed of response may also be a criterion. However, the preheat requirements of products vary greatly, depending on the thermal demand of the assembly and the drying properties of the flux specified. For this reason, many wave soldering machines have modular preheat systems that can be reconfigured on site for a specific application.

Whatever the set-up of preheaters in a machine it is most important that the whole board receives the same amount of thermal energy, because uneven preheating is a dangerous source of soldering faults. However most modern soldering lines give a warning if a heater in the preheating section should fail; some even prevent further boards from entering the machine in case of failure. Boards still in the machine must of course continue to travel forward, if they are not to be cooked or get stuck over the solder wave.