See document "Defrost control using 2-stage supply coil"
TANIPLAN TWO STAGE COIL SYSTEM GUARANTEES DEFROST CONTROL AND TROUBLE FREE WORKING DURING COLDEST WEATHER, TOO.
WE HAVE A STANDARD 2-STAGE COIL IN ONE PIECE TO BE USED AS A SINGE SUPPLY AIR COIL. NO PROBLEMS WITH FROST ANYMORE !