We are noticing more and more that staff and managers are shutting off the blower fan (evaporator fan) when they are in the walk-in beer fridge.
I understand that when you are doing inventory that you can be in there for a while and it gets cold.
Wear a jacket & a toque.
Here is what happens: The fan needs to stay on to keep the fridge at or below 38F (3C). When you turn off the fan the fridge quickly warms up. This causes the beer to get warm in the lines that run from the keg to the top of the fridge. Eventually the kegs get warm too if the fan is left off long enough. Warm beer is foamy beer and that puts added stress on your line chiller. Line chillers are designed to keep cold beer cold, not make warm beer cold.
A bigger issue is that condensation develops on the walls which turns to mould. Before you know it the walk-in walls and the line exteriors are covered with a white film, which turns to white powder, which becomes black and then green after a couple of months or so. This becomes compounded if the fan is on-again, off-again multiple times a day, or if you forget to turn it back on after you leave. Recently I was in a walk-in beer fridge at 3pm where the fan was off since 10am and it was 55F. This happens a lot.
Leave the fan on at all times and dress for the cold.