Steam Boiler vs Hot Water Boiler

Steam Boiler vs Hot Water Boiler


When it comes to the steam boiler vs hot water boiler, the operating principles are more or less the same. Both steam boilers and hot water boilers (also called hydronic boilers) involve the heating of water and creation of steam through the burning of fuel. The heated water is transmitted through boiler tubes, while the steam created is circulated throughout the facility with the assistance of radiators.

Although things work in a similar fashion in most instances, sometimes the steam created in steam boilers is gathered in separate containers. In most instances, the burning fuel used in steam boilers and hydronic boilers are the same.

While hot water boilers and steam boilers share several similarities, they do have differences in the areas of application. Because steam boilers are more powerful, these units are commonly used in industrial applications where steam or hot water is required. On the other hand, hot water boilers are commonly limited to applications for heating. Continue reading to learn more about the major differences between steam boilers and hot water boilers.

Steam Boiler vs Hot Water Boiler

Some of the major differences between hot water boilers and steam boilers include heating points, water level and circulation, accessories, cost, efficiency and safety, and water levels and controls.

Heating Points

The intensity of boiling water in hot water boilers is exceptionally low. In most hot water boilers, the heating temperature doesn't exceed 180 or 200 degrees Fahrenheit. In contrast, steam boilers boast an very high intensity of water boiling. These high temperatures are required to transition water into steam. As a result, steam boilers have heating temperatures that are higher around 212 degrees Fahrenheit.

Water Circulation and Levels

While hydronic or hot water boilers must continually be completely filled with water, steam boilers do not have similar or the same requirements. With steam boilers, the natural expansion of steam causes the pipes to fill. On the other hand, hot water boilers must have an electric pump to circulate the hot water.


In most cases, a steam boiler will not require extra accessories. In contrast, a hot water boiler will typically require an expansion tank, a circulator, and a flow check valve. Most importantly, a hot water boiler will require a motorized pump.

Cost of Implementation

The cost associated with steam boiler vs hot water boilers are approximately the same. The cost variations will commonly be based on the type of fuel required, such as oil or gas.

Safety & Efficiency

In comparison to steam boilers, hot water boilers have been traditionally safer. At the same time, the efficiency of steam boilers has traditionally been less than that of hot waters. The reason for this difference is due to the fact steam boilers do not use motor pumps to enhance circulation. Most importantly, the efficiency of the unit will greatly depend on the steam boiler or hot water boiler manufacturer.

Water Levels & Controls

As previously mentioned, hot water boilers require water levels that are very high or up to the top of the water jacket. In contrast, steam boilers have water levels under the top of the jacket to allow for steam generation. Steam boilers have designs that incorporate a sight glass along with a float valve. These mechanisms automatically control the amount of water.

Radiators distribute the steam throughout the facility, and the steam is returned back into the boiler through gravity. As a result, the steam boiler continues repeating this cycle without any fittings, or special control devices, such as automatic bleeders, flow check valves, or circulators.

On the other hand, hot water boilers require several accessories and fittings to be functional. These units have a unique device for regulating temperature called an aquastat, which handles two major requirements:

  • Manages the operating temperature of the boiler
  • Acts as a low voltage transformer as well as relay to manage the circulator

Some hot water boilers require more than one circulator, which requires additional relays or a multi-control panel. Other controls required for hot water boilers include:

  • A regulator to control the water pressure
  • Backflow preventer or check valve to prevent the remigration of boiler water
  • A temperature-pressure relief valve is used to ensure the pressure and temperature is within limits.
  • Expansion tank is used to facilitate the contraction and expansion of water.
  • Manual or automatic air bleeders are necessary due to the impracticality of sealing the heating system.

Corrosion and Scale Build-Up

Hot water boilers and steam boilers may require a variety of water treatment techniques, but steam boilers must have water treatment to prevent the buildup of corrosion and scale. One of the most common techniques used is bottom blowdown.

With hot water boilers, scale build up is not a common problem. Yet, hot water boilers may still have issues associated with corrosion. This is commonly solved by adding oxygen scavenging chemicals.

Contact Applied Technologies of New York

Whether you're looking for a steam boiler or a hot water boiler, Applied Technologies of New York has your needs covered. We are the manufacturers representative for the leading boiler manufacturers in the world.

Our factory-trained technicians and sales engineers will conduct an intuitive needs assessment and help you choose the best boiler for your facility. We provide expert product sales and support to:

Contact Applied Technologies of New York today to schedule an appointment.