Top & middle shelves COVERED with frost/ice, not middle

Obviously that freezer is not achieved the required temperature. There are several reasons for that:
- Defrosting system is not working, which leads to accumulation too much ice on the evaporator that prevents heat transfer and reduces air circulation despite the fan is running.
- The problem with draining condensate after defrosting cycle which also leads to accumulation of ice.
- Leaking gas from the cooling system (reduced cooling capacity)
- Faulty compressor

Dado

Just had this issue. Freezer is packed usually & suspected airflow. Emptied bottom 2 shelves & vent strip was solid frost. Bottom 2 shelves were filled w/ solid roasts & other solid large items. Used blowdryer & currently waiting to see if it begins freezing top shelf.

Things you can do to cut down on frost.
1.make sure all seals fit flush to frame.
2.use a thermometer and set freezer to -18c(beef will keep upto 12months).
3.wrap all food as airtight as poss.
3.do not overfill,leave space for air flow through drawers/shelves.
4.defrost every 2/3 months in humid conditions using clorine bleach to clean interior,and dry thoroughly.(leave door open to dissipate clorine gas.)

it may be that the door is open a lot witch lets in warm air that go's to the top of your freezer and turns into ice so there maybe nothing wrong with your freezer, in winter we heat the house up and close all the windows this holds in the damp air,, in the summer it should be ok, but to test it place a thermometer in the freezer is should be about -21*f or there abouts for a 4 star freezer

If this is the type of freezer where the shelves are the evaporator coils, the coolant goes through the shelves(tubing) and the formation of frost is normal and has to be manually defrosted.All the shelves should be as cold asd the top one. The fact that just one has any frost may indicate that it is low on freon. If this is the case you should notice that the freezer doesn't get cold enought.

I would look at the defrost control [sometimes they are defrost clocks]Maybe that the freezer is not defrosting.

have you checked the door seals on the freezer. sounds like its getting air into the compartment and causing the problem.

look to see if the shelves are in fact not shelves but evaporator coils . if the shelf is connected to small tubing, then that tubing flows freon that freezes the shelf. if its clearly not connect to any tubing or piping then its just a shelf and gets residual cold from evaporator shelves. if it is connected to tubing like the others and not getting cold then you have whats called a restriction. . particles have plugged the tubing and no freon is feeding the shelf. if that is happening then consider having a pro recover the gas , unplug the tubing , replace the drier and recharge it. if its an older unit and you are getting by then maybe not worth the expense.

Sounds like a defrost system problem. Could be related to defrost timer, heaters or defrost thermostat. Have it serviced.

An upright freezer that is not frost free will have the coils in the shelves (shelves are non-removeable) and that is where the frost will buildup.  If your model is like this then it will have to be defrosted periodically.  If your not sure then give me the entire model # from the sticker inside the freezer and I will look it up for you.