Boilers & Steam Heating Inspection Glossary of Terms and Conditions

Air vents - Devices that release trapped air from steam heating systems, radiators, or piping. They allow steam to enter the system and help prevent air pockets from interfering with heating.

Automatic water feeder - A device that automatically adds water to a boiler when the water level falls below a specified point. It should not be relied upon to compensate for a persistent leak or excessive water loss.

Boiler / Boilers - Heating appliances that transfer heat to water or another fluid. The heated fluid is then circulated through radiators, radiant floors, or other heat-distribution equipment.

Boiler feed pump / Boiler feed pumps - Pumps that deliver water into a boiler, particularly in systems where the pressure or elevation requires mechanical assistance.

Condensate - Water formed when steam cools and changes back into liquid. In steam heating systems, condensate returns to the boiler for reuse.

Condensate pump / Condensate pumps - Pumps that collect and move condensate back to a boiler or to a suitable drain when gravity return is not practical.

Dry return - A steam-heating return pipe located above the normal boiler water level. It carries condensate back toward the boiler or condensate receiver.

Equalizer / Equalizers - Piping connections between the boiler's steam outlet and return piping that help balance pressure and separate water from steam.

F & T traps - Short for float and thermostatic traps. These steam traps use a float to discharge condensate and a thermostatic element to release air and other non-condensable gases.

Float and thermostatic traps - Steam traps that combine a float-operated mechanism for removing condensate with a thermostatic mechanism for venting air.

Hartford Loop / Hartford Loops - A piping arrangement connecting the steam boiler's equalizer to the wet return. It helps reduce the risk of boiler water draining out through a failed return pipe.

Latent heat of vaporization - The heat required to change a liquid into a vapour without changing its temperature during the phase change. In steam heating, this is the heat released when steam condenses back into water.

Low-water cut off - A safety device that shuts down a boiler when its water level falls below a safe operating point, helping prevent overheating and damage.

One pipe counter flow system - A steam-heating arrangement in which steam travels through a single pipe toward a radiator while condensate flows back through the same pipe in the opposite direction.

One pipe parallel flow system - A one-pipe steam-heating arrangement in which steam and condensate travel through the same piping system in the same general direction in different portions of the system.

Pressure limit switch - A safety control that stops a boiler or burner when system pressure exceeds a specified limit.

Pressure relief valve - A safety valve that opens automatically when boiler pressure exceeds its rated setting, releasing pressure to help prevent a dangerous overpressure condition.

Pressuretrol - A pressure-sensitive control used on steam boilers to regulate burner operation by switching the burner on and off at predetermined pressure settings.

Steam - Water vapour produced by boiling water. Steam heating systems distribute heat by circulating steam through pipes and radiators.

Steam traps - Automatic valves that discharge condensate and air from steam systems while preventing the escape of live steam.

Thermostatic traps - Steam traps that use temperature-sensitive elements to discharge air and condensate while retaining steam.

Water hammer - A banging or knocking sound caused by the sudden movement or impact of water within piping. In steam systems, it often occurs when steam encounters accumulated condensate.

Water level gauge - A sight glass or other indicator that shows the water level inside a boiler.

Wet return - A steam-heating return pipe that remains filled with water and is generally located below the boiler's normal water level.