Freezer rooms can be extremely difficult to keep running at sub -18°C temperatures. The biggest risk at all times is evaporators icing up, which can have the following extremely detrimental knock on effects:
Fan burn outs
Liquid returning to compressors
Room temperature rise
In order to prevent this, it is imperative that a skilled technician is on site inspecting the blowers at least monthly. The technician must observe the evaporators and ensure that defrosting is working optimally and act before any major damage can ensue.
In addition to icing of blowers the technician should also check for air leaks on the insulated structure itself to find the points of moisture ingress before they can cause further damage.