I was at a call this morning for a walk-in freezer. and i discovered the evap coil was iced up. its a new customer i already checked if the drain heater was working, it was. checked if the drains were plugged it was checked if the heaters on the coils were working in defrost, it was. i already made sure it couldnt be anything else but the length of the time in defrost.

when i got there it was set for 4 times a day 6am noon 6pm and midnight. and it was set for 28 mins defrost it was an electric defrost.

as a inspiring tech i thought about the coil being frozen, i considered the length was too short and i raised it to 40 mins long.

my question is is 40 mins ok for a 2 fan evap system
could i put the length a little bit longer just incase? i dont really remember about this part in school but if the length is too long will it jump into the cooling mode if the coils already gets the ice off and now its just making the evap too hot?

wat is the normal length it should be in for?
appreciate the help well in advance