A water flow-proving switch is activated by the flow of water through the discharge piping from a circulating pump.

A ___ is a narrowed portion of a tube.

A ___ tank is a hot water system tank used to absorb changes in water pressure in a forced-circulation hot water heating system.

If accessible, gas lines should be checked for leaks by ___.

Rotary cup burners atomize fuel oil using a spinning cup and high-velocity air.

A(n) ___ is a common type of heat exchanger used to heat the air in a building space.

Cold makeup water reduces overall boiler efficiency because energy is required to ___ the water.

Low-water cutoffs must be checked at least weekly or when local ordinances require.

Low-water cutoffs must be checked at least weekly or when local ordinances require.

In actual practice, most condensing boiler efficiencies are around ___%.