It is essential that you understand all of your options when choosing a commercial boiler. For large businesses, you have production demands that must be met. At a reasonable cost. With minimal downtime. In order to make the right decision for your company, it is important to understand a few key things, specifically:

  • The different types of boilers and how they work
  • Common commercial boiler FAQs
  • How to choose the right commercial boiler for your operation

Lucky for you, we’ve created the ultimate guide to help you get started. Our team at Powerhouse is always happy to walk you through these considerations in further detail. Just ask us!

Types of commercial boilers

There are many types of commercial boilers. Each with its own set of advantages and disadvantages. Below are just a few that might benefit your operation. Understanding the different types of commercial boilers will help you determine the criteria that meet your specific requirements. At Powerhouse, we’re happy to walk you through these industrial boilers in order to determine the one that best fits your needs.

Firetube Boilers

In a firetube boiler, the hot gases from combustion flow through tubes to transfer heat into the water contained in the pressure vessel. Firetube boilers are often for smaller industrial facilities with lower operating pressures. These types of boilers offer a cost-effective heating solution since a typical firetube boiler utilizes a simple design with minimal maintenance compared to a watertube boiler.

There are a few different classifications of firetube boiler designs. Currently, the most common design utilizes one or more large furnace tubes where the flame of combustion is maintained. The boiler doors on each end may be used as turnarounds to redirect flow gases for additional passes through the pressure vessel. The turnaround design utilized in the boiler further classifies firetube boilers as dry back, wet back, or semi-wet back. The difference in turnaround design stems from the utilization of water surrounding the rear wall (wet back) or the utilization of refractory (dry back).

Another classification of design is the number of passes the hot gases make through the water in the pressure vessel shell. Every set of tubes that the flue gas travels through is considered a “pass.” Two-pass, three-pass and four-pass designs are all commonly used. Each of their own advantages and disadvantages. As a rule of thumb, firetube boilers with more passes are more efficient with a higher extraction rate than ones with fewer passes.

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Watertube Boilers

In a watertube boiler, the hot gases from combustion flow between the tubes filled with water. Essentially, watertube boilers are designed to circulate water in tubes heated externally by the fire. These types of boilers operate at a larger capacity with the ability to handle greater pressures and higher temperatures compared to firetube boilers.

Watertube boilers utilize two or more drums (mud drum and steam drum) with specifically bent tubes to allow the transfer of water between the drums. The designs of watertube boilers are distinguished by the configuration of the mud drums and steam drums and are typically classified as A-type, O-type, D-type, or flexible tube, which are described below:

  • A-typeboiler utilizes two mud drums near the outside walls and a single centrally located steam drum with the burner located on the centerline of the steam drum.
  • O-type boiler utilizes a single centrally located mud and steam drum with bent types on either side and the burner located on the centerline of the steam and mud drums.
  • D-type boiler utilizes a single mud drum and steam drum located to the left or right side of the boiler and a large bent tube configuration with the burner located out to the side away from the mud and steam drum centerline.
  • A flexible watertube boiler is similar to an O-type boiler but with a much more complex tube bend configuration to allow for a more compact design, multiple pass flue gas flow, and thermal shock resistivity.

V. Ganapathy does an excellent job illustrating industrial watertube designs in the “Understanding Boiler Performance Characteristics” article.


Commercial Electric Boilers

An electric boiler is exactly what it may sound like - a boiler that utilizes electrical energy. Unlike other boilers, there is no combustion energy being transferred into the water with commercial electric boilers. Electric boiler designs utilize both vertical and horizontal boiler shell orientation and may be configured for steam or hot water applications. Some of the advantages include extremely high turndown, zero emissions, and thermal shock resistivity.

Vertical Boilers

For vertical boilers, the main circular boiler shell is oriented vertically instead of horizontally. Vertical boiler design includes both tubed and tubeless types. This type of boiler design allows for a much smaller footprint, which is ideal for areas where length and width dimensions are too constraining for a standard horizontal boiler.

Condensing Boilers

Condensing boilers are quickly becoming the go-to boilers in the commercial and residential markets. Due to the relatively low temperature of hot water loops in homes and small commercial applications, a condensing hot water boiler is specifically built for high efficiencies that other standard boilers cannot achieve, 90% or higher. Condensing boilers utilize a specially designed heat exchanger to lower the flue gas temperature enough to condense and capture the extra energy from condensation. Steam boilers may utilize a condensing economizer to gain the same energy from the flue gas but are theoretically unable to capitalize on this design inside of the boiler due to the difference between boiler water temperature and boiler exhaust dew point.

Commercial Boilers FAQs

What are commercial boilers used for?

In the simplest terms, commercial boilers are used for transporting heat energy from one area to another in your facility. This may be via steam, water, or even hot oil. The boiler is a pressure vessel to allow heat to be captured and efficiently carried from the boiler room to the point of use. Boilers are used in just about every industry in the world to assist in HVAC, manufacturing, processing, curing, cleaning, and so much more.

When do you replace a commercial boiler?

There are a few reasons you would replace a commercial boiler such as: the cost of repairs outweighs the cost of an upgrade, an upgrade in boiler efficiency results in a quick return on investment for a new boiler, or when the demand or operational needs for the boiler changes dramatically. A knowledgeable boiler company can assist in analyzing your current industrial boiler and advising on whether or not it is time to upgrade.

How long does a commercial boiler last?

The life of any boiler, like a car, is highly dependent on the care and maintenance given during service. If a structured preventative maintenance program is followed, boilers have been known to provide 50+ years of service for some customers. However, with no maintenance, some boilers have been totally destroyed in less than a year. Although the designs of boilers are relatively simple, any experienced boiler technician can attest to the importance of proper maintenance. Establishing preventative maintenance, like our recommended Industrial Boiler Maintenance Checklist, could help to reduce boiler emergencies and costs, and potentially increase the lifetime value of your equipment.

How much does a commercial boiler cost?

Commercial boilers dramatically vary in price based on your needs. While industrial and commercial stock boilers do exist, we often find it to be more beneficial over the long run to design a custom boiler. Each boiler should be designed for and ideally suited for a set range of operational conditions. This is so you pay only for what you need and can exclude some expensive design modifications that may be required for other design parameters.

How do commercial boilers work?

A commercial boiler is a pressure vessel designed to take the energy from the combustion of fuel (gas, liquid, or solid), or an electrical current, and transfer it to water for the production of steam or hot water for export to a facility. In simplest terms, boilers are really just internally fired heat exchangers to export steam or hot water. However, due to the inherent dangers of boiler operation, there are strict rules and regulations in place for the manufacturing and operation of these pieces of equipment.

In the US, all 50 states have adopted the American Society of Mechanical Engineer (ASME) code which gives the requirements for the design and manufacturing of boilers. Only a certified organization may manufacture a boiler with the ASME stamp. The ASME Code provides the criteria for the design and manufacturing for all of the types of boilers that we explain in this article, and the many others that we didn’t.

PWR Steam boiler

How to choose a commercial boiler for your operation?

There are a number of factors that you must consider when choosing a commercial boiler. We know that cost, efficiency and production output are important factors, but you also must consider things that could have long-term effects on your operation. From installation location to weather conditions, you’ll want to make sure you’re thinking about all of the things that can affect your operation. We’ve helped you get started with a list of questions for you to consider during this decision-making process.

  • How much steam is being used by the facility currently?
  • What output type is required of the boiler (i.e. high pressure steam, low pressure steam, superheated steam, hydronic hot water, domestic hot water)?
  • What pressures and temperatures should the boiler operate at?
  • What is the desired efficiency of the boiler?
  • What will be fuel be used for firing the burner (i.e. NG, oil, propane, biofuel)?
  • Where will the boiler be installed?
  • Is the boiler easily accessible or hard to get to?
  • Does the weather (i.e. humidity, temperature, etc.) change significantly throughout the year?

Powerhouse promise

Boilers are our business. We specialize in industrial boilers and can help you choose the best quality boiler for your operation. We take the time to understand your specific needs while keeping in mind the safety, reliability and efficiency of the boiler design. No matter what, we promise that you are set up for success with the implementation and maintenance of your boiler system.


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