Only use back-up boiler when occupancies require additional water.

只有当入住率要求更多供水时，才使用备用锅炉。

youdao

The pressure in the cylinders would go up in proportion to the boiler pressure.

汽缸内的压力会与锅炉的压力成比例上升。

《柯林斯英汉双解大词典》

I then soldered up the top and bottom of the boiler.

当时我焊接起来的顶部和底部锅炉。

youdao

Even the billowing steam, it turned out, was fake: no one had dared stoke up the pre-war boiler.

ECONOMIST: Waiting for Korea��s peace train

Beyond this eco-friendly element, Radiator Labs is integrating a phase change material into its product that can store energy and heat an apartment for up to four hours without assistance from the boiler.

ENGADGET

Replacing an old boiler with a modern version can cut a gas bill by up to 25%.

BBC: Gas prices rising: Can you cut your bill by 15%?