When utility bills were inexpensive, it was easy to overlook how heating and cooling systems were inefficient. Now, the simple fact is that being environmentally friendly has a knock-on effect for businesses by making them more sustainable while also contributing to lower monthly costs. With a focus on removing harmful chemicals from coolant options and improving oft-overlooked components in systems, commercial HVAC trends for 2022 will continue to bring rapid change to an occasionally stagnant industry.

Improved Efficiency in Cooling Towers

Whether passive or active, cooling towers play a crucial role in commercial buildings that rely on chilled water for cooling needs. However, while they have been around since the dawn of steam power (and earlier when one considers the use of similar technologies in the Middle East), they have often not seen the same level of innovation. For example, engineers still talk about the move to better fill material in the 1980s.

Today, several factors can improve the efficiency of cooling towers. Like other HVAC systems, carefully modulated fans are crucial for precise operations control. In addition, aspects like moving to state-of-the-art engineered fill material can maximize system efficiency.

The Move From R-22 toR-410A, and now to R454B Refrigerants

With the end of sales for R-22-based heating and cooling systems in recent years, manufacturers have had to adapt their heating and cooling systems differently. The EPA banned new sales of R-22, commonly known as Freon, because of its contribution to greenhouse gasses and global warming. One of the most common alternatives is R-410A, but it is now up for replacement.

While it has improved heat absorption and distribution properties, R-410A has a high global warming potential (GWP).  The industry is now transitioning to a refrigerant with a lower GWP and is in the A2L class. Most major HVAC equipment manufacturers are designing products to utilize R454B. This replacement has the properties necessary to balance environmental concerns, operational performance, and optimized energy consumption.

Controls, Controls, Controls

There are natural limits to efficiency in heating and cooling systems. Manufacturers have vastly improved part-load performance depending on how systems are designed because of new government ratings for energy usage. Systems rarely operate at 100 percent for long periods. The simple fact is that systems are modeled after use cases that rarely occur in the real world.

Integrated “smart” controls fill in the gap between engineering requirements and the reality of how occupants use the space. By adjusting cooling, heating, and ventilation needs based on actual loads, these controls cannot just limit usage in under- and unused areas, but also based on surge energy pricing, weather, and other factors.

While there are numerous protocols, ranging from BACnet to Zigbee and others, ensuring that the various systems, sensors, and controls can all communicate with each other is an ongoing concern for HVAC systems designers due to the occasional interoperability concerns and the expectations of cost engineering limiting certain manufacturers as options.

The Bottom Line: Education is Crucial

There has been a steady trend toward sophisticated modeling software and incorporating numerous factors when considering heating, cooling, and ventilation design challenges. When it comes to commercial HVAC trends, taking advantage requires more than just skimming product sheets and using the same calculations as always.

It requires partnering with companies that can provide the performance capabilities for alternative options from multiple manufacturers and developing real relationships with other members of the construction team to ensure efficiencies are found throughout the design, build, and commissioning process.

Take Advantage of Commercial HVAC Trends

At Windy City Representatives, we understand that while commercial HVAC trends can seem exciting, they have to fit into a budget and existing design requirements. To ensure that your project takes advantage of efficient technology within scope, contact us today for support.

When an architect begins to design a building, their concept art rarely addresses how the building will be heated, ventilated, and cooled. Moreover, those renderings rarely account for the climate where the building will be located.

Instead, a building systems engineer must design an HVAC system that meets occupants' needs while accounting for climate, federal regulations, initial budgetary concerns, and ongoing energy and maintenance costs.

The first and most crucial consideration is the building envelope and design. After all, you can't select systems that you cannot install in a building. Of course, things become more constrained when considering retrofitting an existing building.

Load Measurement and Sizing

HVAC systems engineers can be conservative in their estimates, and with good reason: no one wants to be subject to a call that their design has failed to meet occupancy loads during the hottest, coldest, or most humid days of the year. Unfortunately, this means that some outdated (but widely used) rules of thumb are used in both manual calculations and even in simulations.

The Air Conditioning Contractor Association, in its manual for residential equipment selection, explains that "the practice of manipulating the outdoor design temperature, not taking full credit for efficient construction features, ignoring internal and external window shading devices and then applying an arbitrary 'safety factor' is indefensible." This is unfortunately just as true of commercial buildings, especially those with variable occupant loads.

A report released by the Department of Energy noted that in climates like Orlando, improperly calculating the cooling load based on the insulation and window design can lead to a 40 percent increase in the recommended system guidelines, from three to five tons for a 2,200 square foot home, or 133 percent. A similar case exists for a model home in Chicago for cooling, where adding safety factors added 1.5 tons of cooling needs.

The simple fact is that not-so-simple calculations are required to ensure that the actual heating and cooling loads are correctly ascertained. The same is true for occupant loads, particularly for office buildings or spaces that see frequent tenant changes.

Modeling for Commercial Building Air Conditioning System Design

Depending on location and building envelope design, a commercial HVAC system may only operate for a total of a few days per year during the coldest and hottest days. Unfortunately, while the Department of Energy has updated guidelines regarding energy efficiency ratios (EER) to include part-load conditions, the new guidelines do not apply to all HVAC systems. More importantly, even the updated IEER only gives a ratio based on three separate load conditions, which may not match the actual operation intended.

Instead, designers must use complex performance data that often can only come from distributors or directly from the manufacturers themselves. Otherwise, the energy usage models may be completely different from expectations. This is just as true for occupancy load and use types.

In fact, trying to account for different use scenarios is one reason why the above issue with oversizing is so commonplace. Engineers rightly understand that they may be blamed if the HVAC system fails to perform in specific scenarios, even if they were not discussed. However, when the design-bid-build or other construction process allows for it, ongoing communication is crucial for maximizing efficiency through continuously discussing requirements and needs.

System Selection

There are two factors in selecting systems to fulfill commercial building air conditioning system design specifications:

  1. How the treated air will be moved around the facility.
  2. What kinds of components will be used to treat it.

In most cases, this may seem simple, with the current standard combination being a variable-air volume system that discharges constant-temperature air at various rates throughout a facility matched with either packaged rooftop systems,  split systems, centralized chilled water systems or distributed terminal systems. However, climate and other factors may challenge typical systems, which could limit potential energy savings.

Airflow Movement

Constant Air Volume

The older standard for airflow around a commercial space was constant air volume, and it's similar to that used in modern homes that are predominantly "single-zone": the air is treated to a specific temperature and then moved throughout the facility.

Adjustments can be made for zone differences by using "terminal reheat" coils, where the supply air can be heated to a certain temperature before entering a specific zone. However, this does not provide as much flexibility as the alternative discussed below.

For large spaces, constant air volume systems still provide significant advantages. They are generally less expensive to purchase and quickly respond to large load swings that shift temperatures. However, they are not the right choice for all situations.

Variable Air Volume

For typical commercial buildings, the first choice is likely to be a variable-air volume system with a dedicated mechanical room for heating and cooling operations. In most climates, this provides the flexibility of meeting different temperature requirements throughout a building without requiring additional parts of the heating or cooling system to be operating simultaneously.

Typical applications include office buildings, schools, municipal buildings, shopping centers, and mixed-use facilities.

Equipment Location and Type

Rooftop Units

Rooftop units are flexible designs that put the building’s compressor and heating system in a box above the facility. Commonly used in manufacturing and industrial settings, they are also options for providing temperature, humidity, and ventilation control in lower structures in an adjunct role to the HVAC plant unit. However, there are limits to rooftop units in terms of the distance the air can travel before pressure and energy losses significantly reduce efficiency.

Chilled Water Based

Because it is impossible to move significant amounts of air over long distances, forced-air systems are not feasible in larger buildings. In that case, designers opt for a chilled water system. The solution (actually sometimes brine to prevent freezing) is generated in a chilled water plant  and then piped to air handlers throughout the facility to provide cooling by absorbing heat from individual zones.

Chilled water systems do carry one key consideration, however. Because they can not incorporate ventilation air into the water, designers must incorporate  ventilation air into the air handling unit to meet ASHRAE's requirements.

Variable Refrigerant Flow SystemsVariable refrigerant flow (VRF) systems are coming into vogue for certain commercial environments. Similar to a multi-split system, no air moves through the system. Instead, the refrigerant flows to different air handling units in zones. This system offers several benefits, including:

  1. Reduced space requirements: Instead of ducting, the building envelope only requires space for the refrigerant piping.
  2. Improved efficiency: Like heat pump numbers compared to a standard forced-air system, a VRF system can have 20 to 30 percent better energy efficiency than conventional options. This is particularly true in part-load conditions.
  3. Simultaneous heating and cooling: While a VAV system tied to various heating and cooling equipment can provide consistent temperature air, it does so at the potential expense of occupant comfort with considerable possible changes in airflow for different temperature setpoints.

However, VRF systems do have some drawbacks. Because they do not bring in any outside air, engineers must ensure that a building is equipped with an outside air ventilation.

Installation, Commissioning, and Interdisciplinary Communication

As noted above, HVAC engineers can’t always consult frequently with other members of a build team. Additionally, they can be held responsible for system issues even if the use case no longer remains within the design specification. In addition, the simple fact of the matter is that even relatively small projects are dependent on the efforts and quality standards of many other teams.

As just one example, even the improper application of window film can drastically affect calculations. Even smaller shifts can have a large effect—changing how cabling is run, for example, can impact VAV systems originally meant to run through ceilings or below floors.

It's crucial for design engineers to work closely with the construction team.

While commissioning is the final stage and should allow for handover of the equipment and responsibility to the property owner, building engineers should monitor the construction process and work with building managers and owners to identify and address potential problems.

Partner with Experts Representing Leading Commercial HVAC Brands

There are very few quick fixes for HVAC design, and front-end engineering is the most crucial part of the process for an HVAC systems designer. A close working relationship with the rest of the build team—as well as ongoing examination and adjustment of the design specifications—is a close second.

Windy City Representatives works closely with leading commercial building air conditioning system manufacturers. We understand how important it is to take multiple considerations like budget and existing systems into account.

Custom air handling units take the definition of the system—a box that includes a fan, filter, and at least a coil—and turns it completely on its head. When debating whether off-the-shelf or semi-custom units make sense rather than floor-up solutions, mechanical engineers should consider not just budget, but building envelope, installation concerns, equipment life expectancy, maintainability, and other specific needs when deciding on custom air handling units and manufacturers.

Baseline Expectations of Construction and Reliability

Since there are far fewer issues regarding cost-cutting with custom air handling units, specifying engineers should be able to expect several things when they work with a manufacturer on a design to implement their specific requirements. These include:

  1. Much longer lifetimes: 50 years, or roughly 2 to 2.5 times the average expectation for an off-the-shelf AHU, is a reasonable expectation for a custom-built unit.
  2. Improved maintainability and acoustic performance: Both can be considered part of the “usability” factors, where engineers who understand their facility maintenance team's needs and organizational acoustical mitigation requirements can provide for easier access and noise attenuation.
  3. Meeting specific energy consumption and recovery goals: By being able to source specific components, like variable-frequency drives, fan arrays, coils, and more, a specifying engineer working with a manufacturer to design a custom AHU can meet very stringent requirements for energy costs.

Understanding How Design Criteria Works with Custom Manufacturers

In an ideal world, an air handler for every building and every need would be mass-manufactured and easily available, but that’s simply not feasible. However, the idea of modular and semi-custom air handling units has created a conundrum for specifying engineers: just how much customization does the project require? Below are some key considerations for engineers:

  1. Unit sizing: In many cases, the overall shape of the air handling unit is a key reason to look for custom options. Truly custom manufacturers will offer a variety of material thickness, variable aspect ratios, and types in terms of the outer envelope, along with thermal breaks and other efficiency/equipment protection features.
  2. Component needs: Custom air handling units come with custom-formed coils and the ability to source a variety of compressors, motors, filtration strategies, and drives. If these need to reach certain specifications, it’s crucial to consider a custom manufacturer rather than one that will try to use off-the-rack coils and a small number of “known components” for use.
  3. Expectations during runtime: Operational expectations are crucial for custom units. This can include noise requirements, bearing lifetime, resistance to corrosive elements, non-standard temperature and moisture conditions, different climates, etc.

An anecdote from one manufacturer might illustrate the last point more fully. Well into the fabrication stage of a custom air handling unit, a company found out that the unit would have to operate in conditions that could include Category 5 hurricane winds of well over 170 miles per hour. The ability to change cross members to ones that had nine times the surface area of the original design simply would not have been feasible in modular construction.

Custom AHUs, Delivery and Commissioning

Many air handling units occupy space on either the grounds outside a building or on its rooftop. Access to some spaces can be a major difficulty, and often why using off-the-shelf options wasn’t possible in the first place. It remains crucial to keep the actual installation process in mind at the very beginning of the design process.

While many contractors use cranes to bring larger components up to rooftops, some factors—for example, doorway openings in historical structures—may limit the ingress of other parts, especially interior AHUs. Finding a combination of properly sized components for requirements and ones that will also fit into the spaces needed for them to end up in the eventual shell can be two separate calculations.

The final issue comes with building and shipping the product. As with any custom-built equipment, custom AHUs need extra time. A reasonable expectation for lead time could be 12‒24 weeks, but it all depends on the components ordered.

Find the Right Custom Air Handling Units for Your HVAC Project

Windy City Representatives represents leading manufacturers of custom air handling units, and we understand how important it is to take multiple considerations like budget and existing systems into account when specifying these units. Call us today at 630-590-6933 for a quote or bid.

Cleanroom HVAC systems may be one of the most complex design challenges for engineers because the standards required for implementation offer many options. The key factors in these types of systems are modeling actual particulate and contaminant generation, space requirements for the end-users, and the energy and filtration requirements for the given standard.

ISO Guidelines for Cleanrooms

The current guidelines for particulate control provided by cleanroom HVAC systems are governed by the International Organization for Standardization, or ISO. It expanded the old U.S. Federal Standard 209E, which included six levels, by adding room air filtration as the lowest level of particulate control and adding two more stringent options.

ISO classMaximum concentration per m^3 of >=.1 micron particlesMax concentration for particles >=0.3 micronsMax concentration for particles >=0.5 microns
9 (room air)N/AN/A35,200,000

While the guidelines are relatively straightforward for particulate filtering, accomplishing that goal is anything but simple. Take, for example, guidelines for recommended air changes per hour (ACH) based on ISO level. Ranges vary, even for rough estimates, from 10 to 30 for an ISO 8 zone from one manufacturer to 15 to 25 from another. As the filtration requirements deepen, the range widens, with rough estimates for an ISO 5 zone ranging from 240 to more than 450 ACH.

Why Cleanroom HVAC Systems Engineering is Complicated

As noted above, there are rough ranges for the recommended air changes per hour for a given ISO cleanliness level. However, the simple fact is that every cleanroom is different, as are the processes involved inside each one. Further, while the ISO standard focuses specifically on particulate control, the activity inside the cleanroom may require tight tolerances in both temperature and even humidity control.

Finally, add the question of whether the zones need to have positive pressure relative to the outside rooms, to prevent contamination, or negative pressure to prevent the release of dangerous diseases, and considerations quickly add up.

Adding even more complexity to the situation, building owners must meet ASHRAE’s 90.1 efficiency standard. Ecologically minded owners may also wish to meet the U.S. Green Building Council’s LEED certification requirements, although these standards are not mandatory.

In addition, HVAC systems engineers must account for the “step-down” rooms. As an example, you cannot go directly from room air to an ISO 6 cleanroom. Instead, you must pass through an ISO 8 zone and an ISO 7 zone to access the cleanroom.

Options for Tackling Cleanroom HVAC Systems Design

There are two major options for cleanroom HVAC design, and both focus on how much makeup air or recirculation is possible given the regulations noted above. While all cleanrooms need some amount of outside air, the major decision is whether a large primary air handling unit is required in the situation.

When it is, the options range between a single air handling unit that may include cooling, heating, humidification, and dehumidification capabilities in a custom cabinet to a smaller air handling unit separate from that of the rest of the facility that is combined with secondary recirculation units. The latter is common where there are multiple suites with different requirements.

With the advent of more advanced control systems, it is also possible to increase the use of outdoor air economizers combined with recirculation systems. This can come in the form of a makeup air system with or without fan-filter modules.

Final Thoughts

While the use of options like fan-filter modules and recirculation units are certainly going to become a necessity for cleanroom HVAC systems that must meet high efficiency requirements, they are also subject to the most variability in terms of potential for HVAC misbalancing.

It has become even more crucial for HVAC specifying engineers to not just produce accurate models of airflow during actual cleanroom usage, but to ensure that the facility manager is completely conversant with ongoing testing, balancing, and retro-commissioning as necessary if annual testing requires it.

Find Cleanroom HVAC Systems for Your Needs

Windy City Representatives works with leading manufacturers of cleanroom HVAC systems; we understand how important it is to take multiple considerations into account when specifying these units. Contact us today for a quote or bid.

Sustainable HVAC systems fight against a conundrum: there are very few spaces in the world that are habitable for humans 365 days per year. However, to keep the proper temperature and humidity in each building might represent up to 60 percent of the energy costs. Given that figure, and the limited quantity of available fuel, sustainability is crucial.

When trying to reduce costs and increase efficiency, specifying engineers generally focus on three areas: improvements to the building envelope and utilizing favorable outside climate conditions, improvements in responsiveness to occupancy, and efficiencies in the technologies used to condition and humidify spaces.

​Improving Existing Technologies

​Recently, innovations and demands from facility owners have combined to drive a number of significant innovations. Now, engineers can look to air handling units, chillers, and boilers that include:

  1. Adjustable-speed drives and variable-speed fans to keep HVAC systems from operating as giant on-off switches
  2. Improvements in system design of fan blades, optimized controls, more efficient transmision designs (no more belt losses or gear losses), and more to allow for improved airflow at varying demands
  3. The usage of variable air volume and heat pump systems to a much larger degree than ever before

​Placing a focus on these technologies, where they are applicable given the building envelope, and the external climate, can help drive down cost and increase sustainability. So, too, can examining the outside drivers of cost in terms of energy.

Where energy usage cannot be modified, the source of production can. Establishing boiler systems that work with cogeneration plants can enable system-wide efficiencies across larger campuses while leveraging solar panels for components with smaller drains can dovetail into system ideas revolving around the envelope and outside climate itself.

​Leveraging the Envelope and Outside Climate

​In an ideal world for heating and cooling, a building would be a completely sealed system and the HVAC systems would only have to adjust for changes created by occupants and the impact of outside weather. Unfortunately, that’s nearly impossible, but sustainably designed buildings do create environments where, to the extent possible, spaces of heavy traffic are minimized through proper traffic design.  Essentially, it would be great if a building’s envelope could be cost-effectively built like a YETI®.

Going further requires designers to make good use of both the HVAC system and the outside climate. Heat and energy recovery systems are already critical in modern HVAC systems design. Improvements will only continue to be made to improve the amount of energy that can be reused in the system.

​Moving further into the future, drier climates that can take advantage of evaporative cooling or the ability to reclaim condensate that is currently lost to drainage are all in the pipeline. Similar advances in making geothermal heat pumps more cost-effective would similarly make it much easier to meet sustainability goals. The cost of drilling wells continues to come down.

The most crucial element of any HVAC system is ensuring that it only works when it must. With the advent of the multi-speed fans and compressors available on newer AHUs and other systems and improving efficiency.  Simply letting an entire system run is no longer necessary or feasible.

However, accounting for the various systems that need to run in different zones used to be difficult, even with centralized controls, when they were mechanical. Building automation and control systems help monitor several factors, including:

  1. Occupant behavior and need.
  2. Costs of running various systems using electricity and fuels.
  3. Current grid costs and weather conditions.

​Factoring these along with usage patterns in various spaces can save money and reduce reliance on fossil fuels, but stakeholders must be aware of the decision-making methods used.
​Other examples of responding to user load may include demand-controlled ventilation, which relies on carbon dioxide sensors rather than estimates provided before construction.

In all of these, the calculus remains the same: maintain occupant comfort by working within the outside environment and what energy it can provide, minimize its impact when it is at cross purposes with heating and cooling goals, and balance first costs against overall building costs when designing building envelopes and HVAC systems.

Windy City Representatives represents leading manufacturers of sustainable HVAC systems and their components, and we understand how important it is to take multiple considerations like budget and existing systems into account when specifying these units. Call us today at 630-590-6933.

If you work with commercial HVAC systems frequently, chances are you’ve heard of variable refrigerant flow, or VRF, systems. However, you might not know just how this technology works—or the benefits it offers in commercial and institutional settings. 

​In a nutshell, a VRF system is a ductless HVAC system which uses either a heat pump or heat recovery system to simultaneously heat and cool multiple zones. Its versatility, efficiency, and effectiveness make it a valuable option for building managers who are considering new HVAC systems. However, it’s worth having a basic understanding of just how VRF systems operate and what makes them stand out. 

​Basics of VRF Systems

​Like other ductless (or mini-split) HVAC systems, a standard VRF system consists of an outdoor unit connected to one or more indoor units. However, in VRF systems, the outdoor unit is connected to its counterparts via refrigerant piping and uses R410-A refrigerant to heat and cool indoor spaces. Because the system can control the flow of this fluid through various evaporator coils, it can heat and cool multiple zones—hence the name “variable refrigerant flow”. This is paired with variable-speed compressors and both indoor and outdoor fans, which contribute to the system’s efficiency and comfort.

​There are two basic types of VRF systems you’re likely to encounter, categorized by how the system cools compressors. Compressors support variable motor speed, which is responsible for the system’s control over refrigerant flow. 

Compressors are responsible for transferring refrigerant to zones, so making sure they don’t overheat is essential. To address this, VRF systems use either an air- or water-cooled mechanism. Air-cooled compressors are connected via a loop of refrigerant, while water-cooled compressors are connected to a water loop. 

Both systems have their own advantages and drawbacks. Air-cooled systems usually carry a lower upfront price tag, as they require no additional parts. However, because they require access to outside air, they can present designers with some difficulties in placement and installation. Water-cooled systems, on the other hand, are more compact and offer more installation flexibility. However, they also tend to cost more than air-cooled systems, as they require additional equipment to maintain the water-loop temperature.   

Generally, the system you choose will come down to what your distributor recommends. Both air- and water-cooled VRF systems offer many features and benefits, and every building has its own requirements. Manufacturers like Samsung offer a variety of both air- and water-cooled VRF systems depending on the ambient environment and your cooling and heating needs.

​Benefits of a Variable Refrigerant Flow System

​So, why would you choose a variable refrigerant flow system over your other options? Simply put, they’re efficient, quiet, compact, and versatile. 

Efficiency and operating costs are where VRF systems really shine. Because they don’t have to heat or cool entire buildings and don’t need to push water or air around the building to run, they use less energy and can cost up to 34% less to run than conventional forced-air systems. 

​This also keeps noise down, as the only sound you’re likely to hear from a VRF system when it’s operating is the fan coil units. In settings like hotels, schools, and offices, this is a major advantage.  

Often, space is a major concern when it comes to HVAC systems. Because they don’t require ducting and their air handlers are relatively small, VRF systems are generally more compact. 

Finally, VRF systems’ ability to heat and cool spaces simultaneously helps occupants keep comfortable while keeping costs down. In fact, since the refrigerant can be modulated to a significant degree, it is easier to keep the system operating at peak efficiency and effectiveness.

​Design Considerations

​There are three issues to keep in mind when considering a variable refrigerant flow system in a commercial space, either as part of a retrofit or in use during new construction. As with any newer technology, VRF units have a higher price tag upfront; although they are less expensive to run, these savings take some time to add up.

Another key factor is the use of refrigerant pipes throughout the system. They may only be able to extend several hundred feet, compared to ducts that can travel several stories. More importantly, there are considerations in case of any potential leakage. Technicians who work with these systems must be EPA-certified to deal with the hazardous material. While it is not toxic, it can displace oxygen and lead to suffocation.

The final consideration is that since the system does not force air through ducts, specifying engineers must be mindful of ventilation requirements. It is important to maintain enough space for outside air ducts and air handlers when considering them for a new project.

​Find the Right Variable Refrigerant Flow System for Your Project

Windy City Representatives works with leading manufacturers of variable refrigerant flow HVAC systems. To learn more about how we can help you find the right equipment for you, call us today at 630-590-6933.

Commercial firetube boilers are just one option for facility managers who are looking for efficient processing and heat servicing through hydronic and steam systems. Trying to select the best models for a given application is contingent on several factors, including space available, the type of water/steam required, efficiency requirements, and maintenance needs. Below, we’ve gone over some key factors to consider if you’re thinking of designing and/or purchasing a commercial firetube boiler.

Firetube Boiler Overview

The firetube boiler is one of the oldest designs; while many improvements have been made over the centuries, it still utilizes a fundamentally simple process: hot gasses pass through symmetrical tubes surrounded by water, thus allowing heat to transfer to the fluid that can remain in a liquid state (hot water) or gas state (steam).

Firetube vs. Watertube Boilers

​As their names imply, the principal difference between watertube boilers and firetube boilers is whether the combustion gasses surround the water, or vice versa. 

Firetube boilers are typically used in commercial settings and have a simpler design than watertube boilers. They are generally easier to inspect, maintain, and repair than watertube boilers. 

However, each has their place. Water tube boilers are crucial for applications requiring high-pressure steam, like for cogeneration plants or large multi-building steam systems. They can handle large swings in demand for steam compared to watertube boilers. 

​In the same vein, however, they are less well suited for spikes in demand, whereas firetube boilers can accommodate brief changes in load. In addition, water impurities can have a significant impact on watertube boilers because of the lower content within the system and potential sediment accumulation.

Selecting Vertical vs. Horizontal Firetube Boilers ​

There is, additionally, the option of using vertical firetube or tubeless boilers in areas where there is an extremely small footprint. These were first used back in the days of steam engines and steamboats, but still have their place in applications where a horizontal box cannot work within a building’s footprint. While they are quick to come into operation, there are often limits in terms of maximum hot water and steam generation due to dimensional limits.

Horizontal Water-Back vs. Dry-Back Boilers

One of the most common differentiating features in firetube boilers is how the combustion gasses are routed after their first pass through the tubes used to heat the water. Each model features a different type of reversal chamber.

The wet-, or water-back, system, has a reversal chamber that is completely submerged in water. They are often more efficient and smaller than their counterparts but can be more difficult to access for maintenance as it can be difficult to access the rear tube sheet.

The alternative is the dry-back system, in which combustion gasses are passed through the tubes and then through a reversal chamber that is lined with refractory. Its chief benefits are that maintenance can be easier since technicians can access fire and water-side components relatively easily. However, it can be less efficient, with energy lost through the refractory material rather than heat transferred to the water

Efficiency and Commercial Firetube Boilers

There is a potential misconception among end users that going to condensing boilers is the only way to increase the efficiency of watertube and firetube boiler systems. In fact, using what’s called a feedwater economizer can be designed into the system and used with either watertube or firetube boilers.

Like a heat exchanger, the economizer works by taking exhaust gasses and passing them through a heat exchanger that transfers heat to the boiler’s feedwater. By raising the temperature of the feedwater, the overall energy required to bring it up to operating temperatures is lower, leading to efficiency improvements. While a firetube boiler provides thermal efficiency of roughly 80‒85 percent, systems using economizers can offer ranges of 87 to 91 percent.

Summing Up: Commercial Firetube Boilers

Every building has different requirements and specifications, so it’s important to consult an HVAC expert before you choose the type of boiler you use. You’ll want to take your heating needs, your budget, and your occupants’ heating needs into account. Modern boilers must work in concert with the building’s hydronic or steam system. 

Find the Right Commercial Firetube Boilers for Your HVAC Project

Windy City Representatives works with leading manufacturers of commercial firetube boilers for HVAC systems. We understand how important it is to take multiple considerations like budget and existing systems into account when specifying these units. To discuss how we can help you find the best system for your needs, call us today at 630-590-6933.

Keeping people safe in both their workplaces and their homes relies heavily on preventing airborne transmission and inhalation of particulates that can cause disease or cancer or irritate sensitive linings and parts of the body. As tested by the Environmental Protection Administration, there are several different air cleaning methods available for commercial HVAC systems. Choosing the right one requires an understanding not just of the particulate and microbial transmission rates, but also the amount of air pressure and air volume your system must provide.

​Types of Filtration and Collection 

HEPA Filters and MERV Ratings

HEPA filters are exceptional in terms of particulate absorption, able to capture more than 99.97 percent of all debris smaller than one micron (or micrometer) in diameter. However, while HEPA stands for high-efficiency particulate air filter, there are different ratings available.

HEPA filters are grouped by MERVs, or minimum efficiency reporting value. It can be somewhat confusing, as the ratings are not based solely on filtration efficiency, but efficiency at certain-sized particles. ​

Electrostatic and Ozone Generators

Electrostatic filters and ionizers charge particles as they move through the air, using electrical forces to assist the removal of certain materials from the air. The key difference between the filters and ion generators is that electrostatic filters operate as a capture type filter within the HVAC system’s air stream and an ionizer generator allows particulates to clump and therefore be captured by standard filters with lower MERV ratings.

Another key difference is that ionizers must be carefully considered because if not operated or selected properly, ozone is a potential byproduct. 

Activated Carbon 

​Activated carbon filtration systems are usually used to supplement other filtration systems in circumstances where fumes and odors are particular issues in the workplace. The carbon helps to capture odor-causing compounds like sulfites and others. 


​The advent of the coronavirus pandemic has highlighted the need for germicidal treatments as part of indoor air quality (IAQ) measures. UV-C light is a compelling option that does not restrict airflow and can help to render bacteria and some microbes inactive. 

Considerations for In-System Air Cleaning Methods

There are two principal questions when considering in-duct air filtration systems: the interior air quality requirements and amount and type of pollutants to clean versus the amount of air that the filtration system needs to be able to clean. For example, high MERV HEPA filters are great for hospital operating theaters and semiconductor clean rooms but will have more restricted airflows than other filtration systems. This higher air restriction may tax existing fan and electrical systems.

In fact, multiple stages of filtration are often required based on the particulate profile of a facility as well as the ASHRAE standards for ventilation based on occupant activity. It’s important to consider how much air a filtration system can handle (CFM and static pressure loss). 

Considerations for Standalone Air Cleaning Methods

​Ideally, a commercial HVAC system will rely as little as possible on floor filtration systems for a variety of reasons. They are usually designed to be temporary additions to spaces and as such are not usually accounted for in terms of airflow measurements and calculations.

Exceptions do exist, and a facility manager may desire or require standalone air cleaning methods for supplemental air cleaning, temporary fabrication projects on a shop floor, a breakdown in the overall HVAC system, or other similar problems. 

​Specify Air Cleaning Methods for Your HVAC Project

Windy City Representatives represents leading air cleaning brands for HVAC applications, and we understand how important it is to take multiple considerations like budget and existing systems into account when specifying these units. Call us today for more information: (630) 590-6933.

Energy Recovery Wheels: Design Basics

​An energy recovery wheel is a relatively simple object compared to the complex machinery found throughout an HVAC system. It is, as the name suggests, a wheel or disc that is filled with aluminum (or another metal with a high heat transfer coefficient), synthetic polymer, or some other plastic that can rapidly absorb heat. It’s placed in the system where the supply and exhaust airstreams come into contact, generally before the main heating and cooling equipment that conditions the air for delivery to the building spaces.​

Thanks to the laws of thermodynamics, where systems seek equilibrium and energy can only be transferred, not destroyed, latent and sensible energy is passed from whichever airstream is warmer to the airstream that’s cooler. Latent energy, or moisture, flows in a similar manner, from the moister airstream to the airstream that is drier. This principle works during both winter and summer:

  1. During the winter, the hot exhaust gasses passing by the cool supply air from outside will warm it up. This decreases the amount of work that the HVAC system needs to do to reach user settings. It can also keep the building more comfortable and healthier by recovering moisture from the exhaust air to keep the humidity in the building from getting too low.
  2. During the summer, the exhaust air is still cooler than the hot and muggy supply air. Not only does the exhaust air help to cool down the incoming summer air, but it can also remove some moisture.

​As mentioned in the summertime example above, energy recovery wheels also play a crucial role in modulating humidity, and reduce the energy consumption needed to dehumidify the air

​Alternative Options

​Energy recovery wheels are the dominant form of energy recovery in modern commercial HVAC systems, but they are certainly not the only option available. For effective transfer of both total and sensible (i.e., including moisture) energy, fixed plate heat exchangers are growing in popularity.​In addition, heat pipes, hydronic glycol runaround energy recovery systems, and other designs are also options for energy recovery. However, only fixed-plate exchangers and energy recovery wheels can effectively exchange moisture or latent energy.

​Benefits in Simple and Complex HVAC Systems

​Energy recovery wheels and their counterparts are crucial parts of the HVAC system because of the ever-growing emphasis on energy efficiency present in both society and new government and industry regulations. The ability to use a relatively passive system like energy recovery wheels in HVAC systems will always limit the strain on other components like compressors, chillers, heat pumps, and furnaces that consume significant electricity and fossil fuels.

Regulatory bodies have taken note. Both the U.S. Green Building Council, which runs the LEED certification program, and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) mandate energy recovery ventilation systems, or ERVs, in new construction on many systems. ASHRAE’s Standard 189.1 also requires minimum efficiency ratings to ensure effective energy recovery installations.

Properly designed ERVs not only reduce the overall energy requirements, but they can make a substantial difference in both new and retrofit projects in terms of the sizes and tonnages of components required.

For example, consider a large auditorium. A properly installed and sized ERV can reduce the room’s HVAC load by about 40 percent for existing components—and lower utility costs as well. This provides more flexibility for engineers who can size smaller air conditioning systems, including air-handling units, fan coil units, and other elements.

​Specify Energy Recovery Wheels for Your HVAC Project

Windy City Representatives represents leading manufacturers of energy recovery wheels for HVAC systems, and we understand how important it is to take multiple considerations like budget and existing systems into account when specifying for these units. Contact us today for a quote or bid.

There are many different designs of boilers, as they have been used in commercial settings for more than two centuries. However, for many HVAC systems, a critical distinction is firetube vs. watertube boilers. Each has their place; in fact, a project may require one of each type, or a series of boilers, to provide the hydronic or steam system with the proper heat supply. Below are some of the key considerations regarding the design, installation, and operation of each system.

Basics of Design

​As the names imply, the principal difference between watertube boilers and firetube boilers is whether the combustion gases surround the water, or vice versa. 

Watertube Boilers

​In a watertube design, rows of symmetrical water tubes are surrounded by hot gases as they transfer heat to the fluid contained therein.  This vessel configuration results in a reduced water volume as compared to firetube boilers. The reduced water volume correlates to additional system pumping considerations; watertube boilers often require boiler circulating pumps and a primary-secondary pumping configuration. 

If you’re considering installing a watertube boiler for your heating needs, they offer several benefits. First, watertube boilers are both lighter and smaller than firetube boilers—a key concern if you’re working to retrofit an HVAC system and space is a concern. 


Image courtesy of Cleaver Brooks

​Firetube Boilers

​Firetube boilers are a bit more straightforward. First, the system runs the combustion gases through tube surrounded by water. This results in a higher volume of water in the boiler. Higher water provides additional thermal capacitance of the equipment, reducing vulnerability to varying flow rates through the boiler. The higher water volume and reduced vulnerability to varying flows allows for simpler pumping strategies.

Firetube boilers are usually used for heating commercial buildings of all sizes. Whether a small multifamily residential building or large educational campus, firetube boilers are available to meet the need.​

Firetube boilers are often physically larger and weigh more. This is an important consideration when dealing with retrofit opportunities as there may be structural ramifications of utilizing heavier equipment.  

​Installation and Maintenance

Watertube Boilers

Watertube boilers have a much higher initial unit and installation cost than their counterparts. Because repairs and maintenance must be performed internally, upkeep for watertube boilers also tends to be pricier. However, watertube boilers can heat smaller amounts of water efficiently, which increases their lifespan significantly compared to firetube boilers. 

Firetube Boilers

​Generally, commercial firetube boilers tend to be more expensive compared to watertube boilers to purchase. This is a result of the amount of material that goes into each vessel type. Cost of ownership typically is less with commercial firetube boilers given their reparability, and operating efficiency resulting from application flexibility means that costs are often similar when comparing the two boiler types.

Maintenance vs. Fuel Cost

A good maintenance program consisting of routine inspection and cleaning is essential to maintaining the efficiency of any boiler and can go a long way towards keeping fuel costs low. For example, a buildup of soot within the tubes no thicker than 1/32 of an inch can reduce the efficiency of the boiler by as much as 12 percent. 

As noted in the example above, that can result in over 15 percent additional fuel usage.Keep a daily log of the flue gas temperature of the boiler to spot potential problems early; an upward trend in stack temperature may indicate that the boiler is in need of cleaning or adjustment. Routine inspections and preventative maintenance will pay for themselves in keeping boiler efficiency up and fuel costs down. See the Boiler Efficiency Guide from Cleaver Brooks for more information.

​Making A Choice 

​Ultimately, both firetube and watertube boilers each offer their own benefits and drawbacks—your choice is likely to be informed by your building’s size, your heating needs, and your budget. We’d recommend consulting with an HVAC professional before making your decision, as no two projects are alike. 

Compare Our Partners’ Firetube vs. Watertube Boilers

Windy City Ventures represents leading manufacturers of hydronic heating units, and we understand how important it is to take multiple considerations like budget and existing systems into account when specifying for firetube vs. watertube boilers. To learn more about our advanced technology and discuss how we can meet and exceed your needs, call us today at 630-590-6933.

200 Windsor Drive
Oak Brook, IL 60523
200 Windsor Drive
Oak Brook, IL 60523
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