heater upper cover

例句：

1. 1. The heater needs to be properly installed and the upper cover should be replaced when necessary.
   加热器需要正确安装，当需要时更换上部覆盖物。
2. 2.The heater's upper cover is damaged, which affects its heating efficiency.
   加热器的上部覆盖物损坏了，这影响了它的加热效率。
3. 3. The technician carefully inspected the heater's upper cover before replacing it.
   技术人员在更换之前仔细检查了加热器的上部覆盖物。