Boilers play a vital role in modern industry and life. Whether they are powering large factories or heating homes and commercial buildings, boilers play an indispensable role. However, with so many types of boilers on the market, especially hot water boilers and steam boilers, the choice has become a difficult one for many people. In this article, we'll take a closer look at how these two types of boilers work, the key differences, and the advantages of each to help you make an informed decision.
Components and How They Work
One of the core components of a hot water boiler is the heat exchanger located inside the furnace. Working in a similar way to a kettle on a stove, the water is delivered to the heat exchanger and gradually warms up under the heat generated by the burner. As the water warms, it expands. To prevent the water from reaching the boiling point (212°F at sea level), the hot water system is designed with an expansion tank. As the water is heated and expands, the excess water flows into the expansion tank, thus preventing the water from boiling. In addition, the hot water boiler is equipped with a high temperature limit switch that cuts off the gas supply or stops heating once the water temperature approaches the boiling point, ensuring safe operation of the system.
Safety devices
The safety devices in a hot water boiler are of paramount importance. A key component is the temperature-pressure safety valve, which has a maximum pressure rating of 30 psi. When the pressure in the system reaches this value, the valve opens automatically, relieving pressure in the system and preventing dangerous overpressurization. At the same time, the safety valve is equipped with an extension pipe that directs the discharged water to within 6 inches of the ground to ensure safe drainage. It is important to note that the safety valve on a hot water boiler is not the same as the safety valve on a steam system or water heater, and its rating must be carefully verified to ensure safe operation of the system.
CONTROL AND CIRCULATION
The operation of the hot water boiler is controlled by a thermostat or control module. When the room temperature falls below the setpoint, the thermostat signals the pump to initiate water circulation. The pump pushes the flow of hot water through an operated switch known as a “water thermostat” (also called an “aquastat”). The aquastat will control the burner's operating status and combustion rate based on the actual heat demand. Simply put, it will automatically turn the burner on or off based on the room temperature demand.
Temperature Setting and Pump Type
The water temperature output from a hot water boiler is not fixed and its setting is affected by a number of factors such as the type of radiators used, the distance the hot water is delivered, the type and efficiency of the boiler. Usually, this temperature is set by an engineer or technician on a case-by-case basis. On the side of the hot water boiler, there is usually a tridicator (three-in-one meter) that displays the set water temperature, the actual water temperature and the system pressure at the same time.
There are two types of pumps commonly used in hot water systems. One is the enclosed pump, which requires little or no maintenance, and the other is the three-piece pump, which is often referred to as a three-piece pump because of its manufacturer, Bell and Gossett. The three-piece pump consists of a motor, bearings and pump body, each of which requires regular lubrication and maintenance and is more costly than the enclosed pump. Using multiple pumps on a single boiler allows for hot water distribution to multiple zones.
A steam boiler is a device that produces steam by applying heat to water. In simple terms, it is a closed vessel that converts water into steam using the heat generated by burning fuel in a combustion chamber. In terms of pressure, traditional steam generators typically operate in the low to medium pressure range (1 - 300 psi, or 6.895 - 2,068.427 kPa), and are more commonly referred to as steam generators when the pressure is higher than this range. Steam produced by steam boilers has a wide range of industrial and commercial applications, such as heating and power generation.
There are various types of steam boilers, commonly including fire tube boilers and water tube boilers. In a fire-tube boiler, high-temperature flue gases flow inside the tubes and heat the water outside the tubes, while in a water-tube boiler, on the contrary, the water flows inside the tubes and the flue gases rush outside the tubes to heat them. In industry, a steam boiler can be used to drive a steam turbine to generate electricity to power a factory, and in the commercial sector, it is often used in central heating systems for large buildings.
Because steam boilers operate at high temperatures and pressures, their safety and maintenance are critical. Steam boilers are more prone to scaling and corrosion problems than hot water boilers, which not only reduces the efficiency of the system, but can also shorten the life of the equipment. Therefore, the temperature, pressure and water level of the steam boiler must be monitored regularly to ensure its normal operation. At the same time, strict adherence to safe operating procedures and regular maintenance is the key to ensuring the safe and efficient operation of steam boilers.
Different Working Media And Principles
Hot water boiler: generates and circulates hot water (usually not boiling), which is transferred to heat-using equipment (e.g., radiators, heat exchangers, etc.) through a circulating pump, and the hot water is heated by circulation in the system.
Steam boiler: generate steam, steam pressure through the steam delivery to the steam equipment (such as steam heating equipment, steam piping, power machinery, etc.), steam condensation back to make up water tank.
Application Areas Are Different
Hot water boiler:
Mainly used for building heating, domestic hot water supply.
Suitable for hotels, schools, hospitals, neighborhoods and other civil buildings, can also be used for some process hot water needs.
Steam boiler:
Widely used in industrial production, such as food processing, textile printing and dyeing, pharmaceutical, chemical, paper and so on.
Can be used to drive steam equipment (such as steam turbine, steam drying equipment, etc.).
Different Working Pressures And Temperatures
Hot water boiler:
Usually atmospheric boiler or low-pressure boiler, high safety factor, the water temperature is generally ≤ 95 ℃ (closed system can be as high as 130 ℃).
Steam boiler:
belongs to the pressure vessel equipment, working pressure ranging from 0.4MPa to several MPa, steam temperature up to 151 ℃ or more (depending on the steam pressure).
Structure and configuration differences
Hot water boiler:
structure is relatively simple, does not require vapor separation device.
Equipped with expansion tanks, circulating pumps, hydraulic balance and other systems.
Steam boiler:
equipped with steam bag, steam separator, steam output piping and so on.
Complex control system, real-time monitoring of pressure, water level and other parameters.
Safety Requirements and Regulatory Differences
Hot Water Boiler:
The atmospheric hot water boiler does not need to apply for pot inspection procedures, more flexible use, simple maintenance.
Low risk, suitable for places without professional operators.
Steam boiler:
belongs to the special equipment, need to obtain the boiler registration certificate, and operated by licensed personnel.
Strict regulation, regular annual inspection, higher safety risk.
Comparison of operating costs and efficiency
Hot water boiler:
Small heat loss in the system, good energy saving, suitable for continuous heating needs.
Low operating costs, suitable for long-term stable operation.
Steam boiler:
High steam loss, high heat exchange efficiency, but heat utilization is not as high as hot water system.
Suitable for intermittent or high heat intensity demand scenarios.
|
Comparison Item |
Hot Water Boiler |
Steam Boiler |
|
Working Medium |
Hot water |
Steam |
|
Operating Pressure |
Atmospheric or low pressure |
High pressure (generally ≥ 0.4 MPa) |
|
Application Fields |
Heating, domestic hot water |
Industrial production, power output |
|
System Components |
Circulating pump, expansion tank, heat exchangers |
Steam drum, steam pipes, safety valves |
|
Safety Regulations |
Usually no special equipment registration needed |
Classified as special equipment; requires annual inspection and licensed operators |
|
Thermal Efficiency & Loss |
Low heat loss, high thermal efficiency |
Higher heat loss compared to hot water systems |
|
Operation & Maintenance |
Simple operation, high level of automation |
Requires professional operation |
Easy Installation and Maintenance
Steam boilers are able to run efficiently for decades after installation and require less routine maintenance. A steam boiler system is a good choice for those who are in the process of renovating their homes, especially in older home remodeling projects in places like Grand Rapids, Michigan. In addition, it is relatively inexpensive to retrofit an existing building with a system that is adapted to a steam boiler. The lower initial investment cost allows homeowners to continue to benefit for decades to come.
Saving on Energy Costs
While hot water boilers and steam boilers are each unique in terms of energy efficiency, steam boilers are more unique in the way they save energy. It uses energy primarily in the process of heating water to a boil to produce steam, while less energy is required during the heat transfer phase of steam. As a result, steam boilers are able to better utilize their energy-saving benefits in extremely cold environments or in older homes that are poorly insulated. For example, in many historic buildings in downtown Grand Rapids, steam boilers are still operating efficiently today, providing warmth to the building while effectively reducing energy costs.
Zoning and Flexibility Options
Hot water boiler systems offer a wealth of zoning and flexibility options. Homeowners are free to mix and match a variety of cooling devices according to the functions and needs of different rooms. For example, a plumbed-in skirting radiator can be installed in the living room, a plumbed-in radiant floor in the kitchen, and forced-air heating equipment in other rooms. It is even possible to add special heating devices such as plumbed heated towel rails. In addition, hot water boiler systems are even more advantageous when it is necessary to extend the heating system into new rooms, such as a finished basement, attic or garage. By eliminating the need for extensive floor and ceiling ducting, as is the case with forced-air systems, not only is space saved, but installation costs are also reduced. At the same time, by having individual radiators for each room, users can precisely control the temperature in each room for a personalized comfort experience.
Reliability and Efficiency
hot water boilers excel in reliability and efficiency, which is comparable to, if not better than, traditional forced-air heaters. Upgrading to a hot water boiler system is a smart move for those still using older forced-air heaters and water heaters. Not only will this replace two older units with one efficient system, reducing energy consumption and energy bills, but it may also qualify for energy efficiency grants associated with the use of energy efficient equipment. In addition, users can also choose modulating boilers, which can automatically adjust energy consumption according to the actual hot water demand, further improving energy efficiency and realizing the goal of energy saving and emission reduction.
Conclusion
In summary, there are significant differences between hot water boilers and steam boilers in terms of working principle, energy efficiency, maintenance requirements and application scenarios. Hot water boilers are suitable for places that require higher precision of temperature control, smaller building scale and flexible zoned heating, such as family houses, small commercial buildings, etc. Steam boilers are more suitable for large-scale buildings. Steam boilers, on the other hand, are better suited to large buildings, industrial production, and the heating needs of cold regions, due to their advantages in large-scale heat transfer and in dealing with extreme cold environments. When deciding which boiler to choose, it is recommended that you consult with a professional HVAC engineer, who will be able to provide you with the most suitable solution based on your specific needs, building characteristics, and budget to ensure that your heating system is both efficient and economical.
