Steam Heating System

What is a steam heating system?

A steam heating system is a prevalent type of convection heating system seen in older dwellings. A steam boiler is a device that uses thermal energy to make steam from water. Oil or natural gas boilers are the most common types of steam boilers. Because steam boilers run at a greater temperature than hot-water boilers, they are intrinsically less efficient and more difficult to operate and maintain than their hot-water counterparts.

How a Steam Boiler Works

A cast-iron tank filled halfway with water is at the heart of a steam boiler. The water is heated by a burner beneath the tank until it turns to steam. The steam rises to each radiator in the house via a series of supply pipes. The heat from the steam is transported to the radiator (and through air convection into the room), causing the steam to condense and convert back into water. The water returns to the radiator via return pipes, where it is reheated for the following cycle.

Types of Steam Piping Systems

In most homes, steam boilers are either one-pipe or two-pipe systems. The same pipes are used to deliver steam to the radiators and return water to the boiler in one-pipe (or single-pipe) systems. Steam rises to the top and water descends down the same pipes. A two-pipe system is more modern, as it separates the steam supply and the water return pipework.

Looking at a radiator is a simple approach to figure out what type of system you have. A one-pipe system is one in which just one pipe is connected to it. A two-pipe system is defined by two pipes located on opposing ends of the radiator. Another indicator is the lack of temperature control at the radiators in one-pipe systems; they must be turned on or off completely.

Air Vents in Steam Systems

With each heating cycle, both one-pipe and two-pipe steam heating systems require venting to drain air from the system. To allow steam to enter the radiators, air is driven out through vents. Each radiator in a one-pipe system has an air vent or valve. The hissing sound associated with antiquated heating systems is caused by them. The air is released from a two-pipe system through a steam trap vent on the water return pipeline.

Steam Boiler Controls

Steam boilers have several critical features to ensure safety and proper operation:

Pressure gauge and regulator: Monitors pressure and shuts off the fuel supply to the boiler if the preset pressure level is exceeded
Temperature and pressure relief valve: Releases steam if the pressure gauge/regulator fails and pressure builds dangerously high inside the boiler
Water level sight glass: Clear glass tube that reveals the water level in the boiler
Low-water cutoff: Shuts off the system if the boiler’s water level drops below the minimum level

Maintaining a Steam Boiler

Steam boilers are generally reliable, lasting 15 to 30 years or longer, but they require more maintenance and regular inspections than, say, a gas furnace. Many steam boilers should be checked weekly to ensure that the water level is correct. Overheating can harm boiler parts if there is too much water, and too little water wastes energy. A decline in water level might also suggest long-term issues like leaks or valve failures.

Another regular maintenance task is flushing out some of the water to remove sediment and prevent problems with low-water safety valves. This is usually a simple process of draining a bucket of water, then refilling the boiler with the same amount of fresh water. A quick flush and visual inspection of the boiler controls is good weekly practice.

In addition to homeowner maintenance, boilers should be checked by a professional at the beginning of each heating season. Boiler technicians test critical controls and safety features and conduct a thorough visual inspection to troubleshoot potential problems. Since most homes with steam boilers have very old systems that are costly to replace—or to convert to another type of heating system—it really pays to follow a regular maintenance schedule to keep your boiler running as long as possible.

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Last Updated on 4 years ago