1. What material(s) are you running?
The material or materials you are drying will influence almost every decision you make about a dryer and, if you are running many different materials, you’ll want to specify it with your most challenging material in mind. But different materials require different things from a dryer, particularly when it comes to temperature setpoints. PET, for instance, needs to be dried at 350°F (176°C), while some PETG dries at 140°F (60°C). If you are running PETG, you may need a precooler in the system, while you don’t need one with PET.
Other material related issues include volatiles. If you are running a material that gives off volatile compounds during drying, you need to specify a volatile trap to prevent desiccant contamination. and, if you are drying a material that is sensitive to over-drying (PET for instance can degrade if overheated, and certain nylons actually lose mechanical properties if too much moisture is removed) you should consider a temperature set-back feature that monitors return air temperature and automatically reduces drying air temperature to keep the process stable.