What Is A Boiler

How Does A Boiler Work?

Though the roots of boilers were actually in heavy industrial applications, such as transportation and machine power, today boilers are an efficient means of home heating in residential properties. In residential settings, boilers can integrate with heaters and furnaces to some level to help provide heat and complement an overall HVAC system. They may also exist as standalone heating appliances. In this post, we'll cover more about boilers, how they work and everything else you need to know about them. Here's a closer look:

Boilers 101: What You Need to Know

What is a boiler? Simply put, it's an appliance that works to turn water into steam. More specifically, it's a tank that's often tucked away in a utility closet, crawlspace or in your basement that works to heat water under pressure. Boilers have various inputs and outputs to help them acquire water, a fuel source for operating (usually either gas or electricity) and a means for heat/steam distribution. We'll get into more of the boiler components and how they all work together in the next section.

How Does a Boiler Work?

How does a boiler work? This can be a difficult question to answer, simply because there are various different types of boilers, and it depends on the one that's installed and working in your home. Before we get into the different types of boilers and how they help generate heat, let's first touch base on the common components that make up the boiler:

A Boiler's Makeup (Gas Model) and Other Information

• Burner: In the case of a gas boiler, this is where the fuel source (gas) would come into contact with the air to combust.
• Heat exchanger: Following combustion, the heat produced would be sent into the heat exchanger. This is where the transfer takes place, going from gas to a water state.
• Piping: After the boiler generates steam, it is transferred throughout the property via pipes. 
• Valve: An accessory on gas boilers, these valves allow the boiler to receive the fuel source necessary to ignite the pilot light and burners so combustion can take place.
• Vent: Proper ventilation of combustion gases is important to prevent the buildup of carbon monoxide within a property. Boilers should be installed so that they vent these gases outside of the home.

The above is an example of a gas boiler makeup, but it's worth noting that boilers may be powered by electricity or fueled by oil as well. Oil boilers perform similarly to how gas boilers work, with a combustion chamber and a heat exchanger. Electric boilers are popular in places where gas and oil aren't readily available, and they use electricity to heat the water rather than a combustion process. Electric boilers tend to be more environmentally friendly than those that run on oil or gas, but they also tend to cost more to operate and maintain.

Aside from fuel type, boilers are classified based on pressure and temperature, their form of heating (more on that below), their size and/or capacity, and any advanced waste recovery features that they offer. Curious about how furnaces work and if it could be a more efficient alternative to your boiler? Check out our guide on how does a furnace work or view the different types of furnaces available for residential properties.

Form of Heating

There are two main ways that today's boilers deliver heat to the rest of the property: steam heat and hydronic heat. Both have their share of pros and cons, which we'll cover below:

• A boiler that produces steam heat is more of a traditional method. In this method, water is heated in the boiler until it boils. When it boils, steam is created. After steam is created, it'll rise to the highest point within the boiler system. If you can recall from your grade school science classes, you learned that hot air always rises. In a boiler, it'll usually rise to the radiator, which thereby acts as the heat exchanger, distributing it. 

• Hydronic heat is a more modern-day method of heat generation where water heats up within the boiler to a designated set temperature, and then disperses to other radiators that are located throughout a property. The heat is then distributed through these radiators to the various rooms and areas in a property. This type of system relies on a series of pumps to help distribute the heated water to the radiators in order to heat the property.

When it comes to efficiency, steam boilers tend to be less efficient than those that disperse heat via hydronic heat. This is because a lot of energy is required to boil the water than what is required to just heat it. However, one benefit to going with a steam boiler is that there's no need for a circulating pump, as there is in a hydronic heat boiler that pushes the heated water throughout the home.  For a complete overview and comparison on which system is best suited for your house view our homeowner guide on boilers vs furnaces.