Construction Concerns: Heating Boilers

Article and photos by Gregory Havel

Boilers have been with us since the beginning of the Industrial Revolution, around 1800. The earliest boilers generated steam for mills, locomotives, and ships; their excess capacity was used to heat rooms. Smaller boilers were developed to be the heart of central heating systems for buildings. The earliest heating systems used steam in cast-iron radiators to heat rooms. Since the steam is about the same temperature no matter what the outdoor temperature, buildings were often overheated in mild weather and uncomfortable in frigid weather. Although these systems are difficult to control and inefficient users of energy, some of them are still with us.

By 1900, boilers heated buildings using hot water in cast-iron radiators. The earliest systems circulated the hot water by gravity. Warmer water is lighter and is pushed upwards through the pipes and radiators by the cooler water that is descending in larger pipes back down toward the boiler, usually in the basement or cellar. The water temperature could be adjusted manually by a thermostat, so that in mild weather the water would be only warm, and in frigid weather it would be hot.

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The development of reliable electric pumps in the early 1900s led to the replacement of gravity systems with hydronic systems using electric pumps and thermostats to control the water temperature and turn pumps on only when needed. The boilers were much the same until the 1950s, when fuel costs became a concern. Boilers were usually steel or cast-iron hulks (photo 1) that took up much of cellar or “boiler room” space. If insulated at all, they were insulated with asbestos cement, and often sent more than half the heat value of their fuel up the chimney. Some of these boilers have been well-maintained and are still in use today.

The earliest fuels were coal and wood. Fuel oil burners became common in the early 20th century, even in areas with coal mines; and were advertised as clean and trouble-free compared to a boiler with a coal stoker and ash pit. Natural gas began to replace fuel oil in the Midwest and other parts of the United States after World War II.

In the 1970s, fuel prices rose dramatically, even more rapidly than the cost of living index. It was already known that the boilers in use were inefficient, but low fuel prices offered little incentive to develop truly efficient systems, although residential heating boilers had already evolved into more compact and efficient units. Homeowners wanted to use their cellars and basements for living space, not to house a huge, dirty boiler.

Residential heating boilers’ efficiencies continued to evolve and were applied to commercial heating boilers, reducing their size and significant changing their appearance.

The boiler in photo 1 was used to heat a college dormitory building with an attached gymnasium and recreation facilities, using a hydronic heating system with automatic temperature control. It’s what we often visualize when someone mentions “boiler.”

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The boiler in photo 2 is one of several used to heat a college dormitory building of similar size, using a hydronic heating system. Instead of a central boiler room, four of these units are located in closets and utility rooms scattered throughout the building.

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The boilers in photo 3 are in a conference center, and were installed to replace a boiler similar in size and capacity to the one in photo 1. The modern, high-efficiency boilers in these photos don’t even look like boilers. They use sealed combustion chambers, bringing in outdoor air through PVC pipes or metal ducts rather than using air from inside the building. The combustion chambers and heat exchangers are so efficient that the stack gas is often below its dew point, requiring a trap and drain to remove the condensed moisture. The flue gas is only a few degrees warmer than the water circulating in the heating system; in residences, is often vented through Schedule 40 PVC pipe. Because condensed flue gas is corrosive, stainless steel is becoming the most common material for these boilers, replacing copper, steel, and cast iron.

When we are doing primary search in a building or investigating a reported gas leak or carbon monoxide alarm activation, we must be aware that the appearance of boilers and heating equipment has changed as the technology has evolved. Although we may still find a boiler like the one in photo 1, we are more likely to find one that looks like a filing cabinet or sheet-metal box, like the ones in photo 2 and 3. We must also remember that just because we have found one of these does not mean that we have found the only one.

Another significant point in developing prefire plans and strategy and tactics for an incident, is that in a modern building, it is less expensive to build and more energy-efficient to operate when we pipe the boiler fuel (oil or natural gas) throughout the building, so that the energy will be used where it is needed. Fuel is likely to be piped throughout the building to appliances, rather than only to the boiler room and kitchen.

For more information on modern boilers, fuel efficiency, temperature control, and heating systems:
• Visit the Web site of your local electric and natural gas utilities
• Internet search for “heating boiler,” “hydronic heating,” “central heating boiler,” “energy efficient boilers,” and “energy efficient.”
• National Fire Protection Association 54, National Fuel Gas Code.
• NFPA 85, Boiler and Combustion Systems Hazards Code.
• Visit the manufacturers’ Web sites for brands of boilers and controls with which you are familiar.
• Discuss your state and local codes and HVAC and energy efficiency requirements with your local building inspector or a reputable service contractor.

Concerns with small residential hydronic and steam boilers; industrial power boilers; boiler operator licensing; boiler make-up water systems; pressure relief valves; and safety controls will be addressed in future articles.


Click to EnlargeGregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC.

Subjects: Building construction for firefighters, boilers

 

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