Hi-Tech and fashionable appearance and aesthetic design SD series: Anti-dirty monothemic heat exchanger, Timer setting and one week timer program, Large LCD color display, Timely error diagnoses, buzzer alarm, Microcomputer digital control SP series: Bithermal heat exchanger, Timer setting and one week timer program, Large LCD color display, Timely error diagnoses, buzzer alarm, Microcomputer digital control Gas type: Natural gas / LPG / Town Gas Power selections available: 18kW, 24kW