What should you consider when buying or operating a boiler?
A commercial boiler is a long-term investment. Properly maintained, your unit can last 30 years. So, it is important that you consider more than just price when shopping.
Consider the unit’s lifecycle cost.
Since fuel costs are by far the largest single lifecycle cost of a boiler, choose the most energy-efficient unit that meets your particular needs.
Yes, condensing boilers cost much more money than conventional units. But they are significantly more energy-efficient (90-96 percent efficient compared to 70-85 percent for a conventional unit). The savings you realize from a condensing unit will help to repay that cost difference in as little as five years.
As well, condensing boilers are well suited to specific applications. They are particularly effective, for example, at delivering low-temperature hot water for space heating.
Use a modulating boiler.
A boiler that fires at a single input rate heats water by switching a flame fully on and fully off. This method, however, consumes a large quantity of fuel and is highly energy inefficient. In a modulating boiler, the flame is fired to match the boiler load.
Integrate small boilers.
Check your boiler size. Some businesses install too-large boilers to accommodate periods of peak demand and anticipated expansion, but this practice is highly energy inefficient. When retrofitting your boiler systems, consider sequencing several smaller boilers. Fire all in parallel during peak periods and run only the ones needed during periods of low demand.
Try heat cascading.
Multiple high-efficiency condensing boilers can be installed in cascade to satisfy even the largest commercial heat demands. This boiler configuration provides a highly effective and extremely efficient heating system. The boilers are configured to automatically optimize heat, efficiency, and hot water supply to the demands at any particular time. This system of multiple boilers also provides security against interruption of heat, with multiple boilers available as back-up.
Follow these best practices for even more energy savings
By themselves, new high-efficiency commercial boilers can bring real energy and cost savings to your business. But if your company wants to do even more, consider how your boiler functions as part of your larger heating system.
Follow some of these tactics to ensure your system runs at peak performance.
Hire only trained, qualified personnel to run, adjust, inspect and maintain your boiler systems.
Lower return water temperature
A condensing commercial boiler operates at peak efficiency when the water returning to the boiler is lower than the temperature of the condensing flue gas—in the range of 45–50ºC. Otherwise the flue gases will not cool enough to recover the latent heat. If an existing distribution system is designed for high temperature water, look into changes that would lower return water temperature.
Minimize short cycling.
An oversized boiler turns on and off more regularly than a properly sized unit. Such regular—and short—cycling is very energy inefficient. A number of sequenced smaller boilers can easily do the job of a much larger unit and will run more efficiently.
Control combustion air.
A boiler’s air-fuel mixture significantly affects its efficiency. Too little air means incomplete combustion; too much leads to wasted energy. Introduce a control system to monitor and optimize boiler air-fuel mixtures.
Clean your boiler.
The fire side of boiler tubes can accumulate deposits from burning fuel that can greatly reduce heat transfer. Similarly, the water side of the boiler tubes can become clogged by mineral deposits, which also reduce energy efficiency. Hire a professional to inspect and clean your boiler regularly to ensure optimal performance.
Control water blowdown.
Boiler water should be blown back through the unit as part of regular maintenance to clean scale deposits from water side tubes. If you use more water than needed, this “blowdown” process is wasteful. Introduce automatic blowdown controls to measure and respond to blowdown needs and use just the right amount of water for the task.
Use outdoor reset.
Outdoor reset is used in hot-water building-heating systems. Older boilers deliver the hottest water possible to the heating system’s distribution channels. Outdoor reset varies the temperature of the water in the distribution system in response to outdoor temperatures. When outdoor temperatures are cold, water temperature rises; when temperatures are warm, distribution water is cooler. For condensing boilers, this will help lower the return water temperature to the boiler, particularly in the shoulder seasons.
Outdoor reset can lower energy use by as much as 15 percent.
Adding insulation to the outer walls of your boiler can reduce heat loss through radiation and convection.