Some of them can get pretty elaborate with lockout relays, multiple evaporators and such, but the most basic walk-in coolers I have wired normally use a line voltage thermostat inside the box at the evaporator that controls the liquid line solenoid to shut off the compressor on the low pressure control. If itís a cooler only, it generally wonít need a defrost timer setup, because the evaporator doesnít get cold enough, but if itís both a cooler and freezer setup, it will have one. You might also have some door jamb and air pressure vent heaters to connect.
A condensate line heater is normally used in a freezer compartment. Iíve seen them either 120 or 208V, so I would check with the reefer guys on that because it may require add-on GFI/GFP protection.
For the interior wiring, I like to use EMT with pipe hangers, WP compression fittings and LFMC where needed along with WP metal boxes and covers, but Iíve also done coolers with PVC and FS boxes and LFNC where needed that worked out fine. Iíve seen some guys just use LFMC inside the walk-in secured directly on the surface with one-hole straps along regular dry location 4Ē boxes, so I guess it depends on what the walk-in is used for and your local requirements. I your case, they are storing fresh meat, so I think your state sanitary code is going to come into play.
I just use ordinary duct seal to pack the LB other fittings at penetrations and then run a bead of caulking around the outside of the fittings.
HeatCraft is a big name in walk-in refrigeration sytems. You can download other installation literature from their website, but the one in the link below is pretty typical of what you'll see. The wiring diagrams start on page 40.HeatCraft