We have a large outdoor freezer. R22 gas, two air handlers inside the box. The outside compresor cage is with in three feet of the exit of the box. I had a local tech check the freon level earlier in the summer as the temp had been climbing up steadly. We found a lead at the spider on one of the air units and tightened the compresson nut. Filled the system to what his calculations said was full. It now freezes all the way back on the suction line which seems to indicate to me low level of gas. I called and he said no, that is normal. I just would like to understand, is it the wrong spider, thus improper expantion or do I just not understand?

There could be a few different reasons you have a frozen or frost on the suction line. Many of them normal on a outdoor freezer. It is not good to play a guessing game on this subject since the best way to tell is by a ON SITE inspection by a person skilled in refrigeration. This way you will know for sure if there is a problem or not.

Usually these systems have a defrost control and uses hot gas or electric heaters to do the defrost job. You need to have the service man check the unit if you are concerned.