Understanding Boiler Performance - Lindberg Process Equipment

Over the years, the primary technology for heat or process energy generation has been powered through steam and hot water. These days, powerful machines like steam and hot water boilers are joined by electric boilers to provide heat and energy to commercial facilities and residential homes.

Simply put, the efficiency of a steam or hot water boiler hinges on the difference between the energy output and input. When you buy a boiler, the initial investment in the machinery itself is actually the lowest cost. What winds up costing the most over the long run is the fuel investment, so it’s crucial to assess and understand your boiler’s efficiency to save the most money over time.

The most basic measure of a boiler’s performance is assessed by looking at cost versus efficiency. A high-performing boiler will run better, for less. The opposite is true for inadequate machinery.

Through testing and monitoring, a boiler should be able to make it all the way through its expected lifespan. Gas boilers usually outlast electric boilers by a few years, but when maintained properly, both can last ten years at the very least. When you conduct a thorough assessment of your boiler’s performance, whether it’s gas, electric, steam, or hot water-powered, you can determine any necessary maintenance, repairs, or replacements.

Understanding Boiler Performance

There are a wide variety of reasons to test your boiler’s performance. Perhaps you’re considering an expansion of a commercial plant or a remodel of your existing home. Regardless of the project, you’re undertaking, the main factor in understanding boiler performance assessments is the annual fuel utilization efficiency (AFUE).

Annual Fuel Utilization Efficiency (AFUE)

It is standard operating procedure to measure the annual fuel utilization efficiency (AFUE) when assessing a gas or electric-powered boiler’s efficiency. This key indicator helps compare different boiler manufacturers and models.

According to the United States Department of Energy standards, the AFUE is a means to measure how efficient the appliance is at converting energy into expendable fuel. More specifically, it is the ratio of the annual heat output of the boiler compared to the total annual fossil fuel consumption of the appliance.

The Federal Trade Commission requires the AFUE of new steam and hot water boilers to be displayed, so you can accurately comparison shop when selecting a new boiler. While it may seem confusing, understanding the AFUE of your boiler is quite simple. Here’s an example:

If the AFUE of your gas-powered boiler is 95%, that means 95% of the fuel energy becomes heat and 5% is lost through a chimney.

Electric boilers don’t have chimneys, and the level of energy loss is low. Most electric boilers have an AFUE between 95-100%. While this high AFUE may seem attractive, the cost of running an electric boiler can be higher than that of a gas boiler in some areas.

The AFUE of a boiler system is the primary assessing factor for efficiency. However, there are a few unique efficiency characteristics between gas and electric-powered boilers to consider when completing an efficiency assessment.

Gas Powered Boilers

Just as the name implies, gas-powered boilers require fossil fuels to create energy for homes and commercial or industrial buildings. Gas consumption and loss are the primary focus of performance testing for gas boilers. Gas boilers are typically used in industrial and manufacturing processes.

Besides the AFUE of the boiler, there are a few other key factors to assess when measuring the boiler’s efficiency:

  • Combustion efficiency: This indicates the boiler’s ability to burn fuel at efficient levels—the less fuel needed to create energy, the more efficient the appliance.
  • Thermal efficiency: This determines the effectiveness of the heat exchange within the system. If a significant amount of heat is being lost in the heating process, the boiler is not efficient.
  • Direct efficiency: This is the percentage of total heat output versus total heat input.
  • Indirect efficiency: The indirect efficiency can be calculated by deducting losses taking place within the boiler from 100% efficiency. Other factors considered in indirect efficiency are:
      • Stack losses
      • Radiation losses
      • Blowdown losses
  • Other efficiency measurement parameters: On-off losses, convection losses, radiation losses, etc.

Electric Boilers

In recent years, electric boilers have become a popular choice for homeowners because of the attractive AFUE values they display. However, an electric boiler can be incredibly expensive over time. Depending on the area you live in, electricity may be a more expensive energy source than alternatives like fossil fuels.

Electric boilers usually have an AFUE of 95% or higher. Typically, the AFUE is closer to 99-100% efficiency, so it’s not as critical to assess other performance indicators of an electric boiler. However, it is important to consider the high carbon emissions at electric power stations.

For homeowners, the numerous advantages of an electric boiler are enough to make the switch. Aside from the near-perfect efficiency rating, other benefits of electric boilers include:

  • Minimal maintenance and service costs
  • No carbon monoxide emission risks
  • Small size compared to older boiler models
  • Solar-power compatible
  • Quiet
  • Ideal for homes and buildings not connected to gas lines

Many factors contribute to the performance and efficiency of a boiler, and it’s essential to understand the advantages and disadvantages of different models and boiler types. Luckily for home and business owners, Energy Star, a government-backed entity, compiled a list of the most efficient boilers currently on the market.

When to Replace Your Boiler

There can be a wide variety of reasons to replace your boiler. Obviously, when repairs become too costly and the machinery is running way below peak efficiency, it is an ideal time to replace your boiler. Additionally, if your commercial plant plans on expanding its production processes, higher efficiency boilers will be necessary to meet your new needs.

When looking for a new boiler, work with a professional processing equipment sales representative to help you understand and compare AFUEs and other performance stats to ensure you make an informed decision before you buy new equipment.