How Does a Steam Boiler Work?

While steam heating systems aren’t as common as they once were, they’re still around and kicking. And if you have one, it’s probably never really crossed your mind how your system keeps you warm and comfortable in colder weather.

If you’re thinking of adding one to your home or just curious about how your trusty system works, you might be asking: how does a steam boiler work? We’ll explain how your heating system operates, its pros and cons, and how to maintain it so it stays running when you need it.

How Do Steam Heat Systems Work?

A steam heat system uses a steam boiler to heat water using a combustible fuel source—gas, oil, or electric burner—to its boiling point. Once the water reaches this point, it evaporates, turning into steam that’s then distributed to radiators throughout your home. A system that uses a heat pump instead of a boiler differs because it uses electricity to move heat air in your home.

When your steam heating system’s thermostat detects that the air temperature is below the desired level, the radiators use the heat from the steam to make the room warmer. 

Once the steam starts to cool, the condensation process takes over and turns the steam back into water, returning to the boiler where it’ll be heated again. 

However, how it happens precisely depends on whether it's a one- or two-pipe system. A one-pipe system means that the steam comes through and condensed back into the boiler through the same pipe. A two-pipe system uses one pipe for the steam to come through and the water condensed through the second pipe.

Pros and Cons of Steam Boilers

Whether you’re doing a full-scale remodel of your current home, buying a new one, or comparing your existing heating system to its alternatives, find out what makes a steam heat system shine and what its flaws are here.  

Pros

Steam heat systems can last for a long time, run quieter than other systems, and allow you control over which rooms you heat (by turning on radiators or turning them off).

Cleaner Airflow

When using a forced-air heating system, the air is continuously cycled through air ducts to heat your home. During this process, dust mist, pet dander, dirt, pollen, and other particles can float inside your duct system and circulate throughout the air in your home, potentially creating allergy problems.

But, steam heating uses a radiator and not ducts to heat your home, so you won’t need to worry about allergens or debris circulating throughout your home on loop.

Long-Lasting

When a steam boiler is maintained and in good condition, it can last homeowners 20 to 25 years on average. While on the other hand, a forced-air system lasts for around 15 years.

More Reliable

Newer, modern heating systems come with more moving parts. And when there’s more to maintain, the possibility of something breaking increases. A steam heater uses fewer parts to heat up your home, making it more reliable to use and less likely to break when it’s cold outside. 

Quiet Operation

Another nice feature of a steam heating system is that it’s quieter to operate than traditional forced-air systems. You can typically tell when a forced-air heating system is on and running since you can hear the air blowing through the ducts throughout your home. On the other hand, steam moving through pipes makes less noise.  

Air Control

Sometimes you don’t need to heat your entire home—only some of it. If you only care that your bedroom feels nice and toasty, you can distribute your system’s heat accordingly. 

Contrary to popular belief, closing unused vents in a furnace heating system is a common heating mistake. It places a strain on your HVAC system and is less efficient than leaving it open. But controlling air temperature by room isn’t a problem for a steam heater.

Cons

However, steam heat systems require a lot of maintenance and aren’t as efficient as many other systems. 

One Temperature Throughout Home

While you can control which rooms get heated, you can’t control the exact temperature of each room since it’s heated the same. If you’re someone who prefers to keep certain rooms a little cooler (or warmer) than others, a steam heater’s uniform temperature is something to consider.  

Heating Efficiency

Steam heating systems aren’t as efficient as their more modern, energy-efficient counterparts. This lower efficiency means that these systems don’t heat an area evenly, resulting in a higher energy bill since it’ll take longer to heat a space. 

High Maintenance

Steam heating systems can keep you warm in the cooler months, but it’s not just a set and forget it until the season is over heater; they require regular maintenance. Each part needs to be checked at least annually by a local HVAC pro, and the high maintenance needed to keep it running has many hesitant about these systems. 

Slow Start-Up

When the temperatures drop, you’ll want to warm up immediately. But steam heaters can pose a problem since it can take some time for the pipes to heat up and start pumping steam through your home.

Types of Steam Boilers

There are two main steam boiler types: fire tube and water tube. However, you might also hear professionals and manufacturers refer to steam boilers by the kind of fuel they use or the pressure they produce.

• Fire tube steam boilers: Combustible gases inside a tube are immersed in water. When the gases traveling along the tube are heated, this warms the water surrounding the tube.

• Water tube steam boilers: Water is contained within the tubes rather than around them. The flames and gases are on the outside in a combustion chamber. The heat on the outside of the tubes warms the lesser quantity of water inside the tubes quickly. These boilers are complex, so their installation and maintenance requires more help from a local boiler pro. 

• Electric boilers: These boilers generate steam using electrical elements to heat the water.

• Gas boilers: Low-pressure water and fire tube steam boilers are often powered by gas. 

• Oil boilers: Water and fire tube boilers operate very efficiently and require less maintenance when powered by oil.

• Low-pressure boilers: These boilers transfer heat at pressures up to 15 PSI (pounds per square inch) with a maximum temperature of 300 degrees Fahrenheit. 

• High-pressure boilers: These boilers are commonly seen in large-scale industrial environments, where they’re used to power machinery. They generate pressure between 15 and 800 PSI and temperatures over 250 degrees Fahrenheit.

How to Maintain Your Steam Heat Systems

To keep your system pumping out the steam you need for the warmth you want, you’ll need to perform year-round maintenance procedures and learn how to reset your boiler, how to light your boiler, and other important basic functions. Here are a few ways you can help keep your steam boiler system in tip-top shape:

• Free up any blocked vents.

• Inspect the steam boiler for leaks.

• Keep the area around your steam boiler clean. 

• Check if the water levels are in the correct range monthly.

• Test the pressure relief valve every six months to see if it’s working.

• Contact an HVAC pro to drain your steam boiler every six to 12 months.

• Check that the radiator’s inlet valve is fully open or fully closed, not in between.

• Check steam pressure levels every month to make sure they’re in a normal range.

• Keep each radiator gently sloped toward the steam inlet pipe to prevent your radiator from knocking.