My Rheem unit tripped off yesterday. I went down to have a look and I noticed a puddle on the floor. Initially, I thought the condensate drain sump pump had died but when I took the panel off to look at the coils for the Rheem I noticed a block of ice on the coils and on the cooling transfer plates.

I can get the ice off and the unit will run but what is causing the ice accumulation? I do not see any freon to indicate a leak on the chill side of the coil. It appears to be condensate that has led to the ice.