要用到一台燃气热水器,PID图上指出用天然气做热源,业主指定了型号和供应商,是一台间接式燃气热水器(indirect water heater),但是厂商的资料上提到“indirect water heaters combined with a high efficiency boiler provide the most efficient, economical method of heating water”,可是PID图上并未提到有锅炉与之配套,天然气是直接送至热水器的,所以我糊涂了,向大家求助!到底间接式燃气热水器是怎样工作的?' p/ |0 l" o9 [- \, L4 g! p