What does XH mean?

XH is generally the two letters of Chinese Pinyin, but in the HVAC industry, it represents a representative of general equipment, which means fresh air ventilator, a high-efficiency and energy-saving total heat exchanger. For example, SE-XH-20D stands for an efficient and energy-saving total heat exchanger with 2000 air volume, which is installed in the ceiling and is a general representative. At present, some designers like to express it as SE-XF-20D, which actually represents the same kind of equipment, but.