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By Greg Hughes Three boiler types loom large among conventional (non-condensing) commercial water boilers used for process or space heat, with input sizes of 400 MBH and up: those with cast iron sectional, fire-tube and water-tube heat exchangers. For a variety of reasons, the latter two have been most prevalent in the commercial process heating Read more

By Greg Hughes

Three boiler types loom large among conventional (non-condensing) commercial water boilers used for process or space heat, with input sizes of 400 MBH and up: those with cast iron sectional, fire-tube and water-tube heat exchangers.

For a variety of reasons, the latter two have been most prevalent in the commercial process heating market. Advantages include relatively compact size, lower standby heat loss, and the speed with which heat can be generated and delivered into distribution piping.

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A Thermal Solutions AMP water-tube boiler is rated at 97% efficient. The stainless steel, modulating-condensing boiler line offers a size range of 1,000-4,000 MBH.

First out of the gate for a wide range of uses was the fire-tube boiler—with early design dating back centuries.  Hollywood gave great prominence to horizontal fire-tube boilers, though few producers, actors or moviegoers were aware of it.  Every time a steam locomotive—aka the iron horse—blew its whistle or raced across the great plains, an uncelebrated fire-tube boiler was doing its part.

Still today, fire-tube boilers offer a wide range of uses.  Within these boilers, fire tubes are immersed in water; hot flue gases produced by the combustion chamber flow inside them. The hot flue gases transfer their heat to the outside water through the conduction.

Water-tube boiler designs, introduced later, essentially invert the fire-tube boiler construct: water is contained within the boiler’s internal tubes.

Water-tube advantages

In water-tube boilers, combustion occurs within the shell that surrounds the tubes, forcing combusted gas over the water tubes for exceptionally fast, efficient heat transfer.

Water-tube boilers offer quick startup and response time to changing conditions with very little standby loss. By design, comparatively little water passes through the heat exchanger; this translates into a smaller footprint and broader range of capabilities and output ranges.

“Their ability to make steam, or hot water, very rapidly, from a cold start, and without damaging the boiler is a beneficial asset,” said Lane Blackwell, Sales Engineer, Service, for Peru, Ind.-based Thornton & Associates,. Inc., a manufacturer’s rep firm. “This is valuable in applications where the systems aren’t running 24/7.”

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Bryan Boilers’ BFIT commercial condensing water-tube boiler series is a stainless steel, modulating-condensing boiler line with ranges from 1,000-4,000 MBH with optional racking system. Image courtesy of Bryan Boilers.

Because the burner in a water-tube boiler is located centrally, most water-tube designs provide higher temperature outputs and higher operational pressures than fire-tub boilers—key advantages for process heating application. Another advantage to the design of these systems is that, as a result of the requirement for water to flow continuously during operation, hot spots in the heat exchanger don’t threaten the operation or lifespan of the boiler.

Water-tube heat exchangers also operate at higher pressures, a capability that can—for steam-producing systems—produce saturated or superheated steam depending on the design and application they’re required for.

Blackwell also points to the advantage of water-tube maintenance, “Or, rather, lack of it. A surprisingly high number of water-tube systems may go several years without more than occasional attention to the water quality [within them], he said. “And, if there would be a need to replace individual tubes, that can be accomplished with hand tools; no rolling or welding. It’s not uncommon for a well-maintained water-tube boiler to last 40+ plus years with little maintenance.”

water-tube boilers, boilers, hydronics, fire-tube boilers, Burnham Boilers, Bryan Boilers, Thermal Solutions Boilers, AMP water-tube boilers

– Bryan Boilers’ BFIT commercial condensing water-tube boiler series is a stainless steel, modulating-condensing boiler line with ranges from 1,000-4,000 MBH with optional racking system. Image courtesy of Bryan Boilers.

“A few years ago, we specified two non-condensing water-tube boilers for a high school expansion project in Cass County [IN],” added Blackwell. “The boilers were 72 and 50 HP in size, and it wasn’t long before facility managers found that they could provide heat for the rest of the school with them, so they decommissioned two old, enormous—and way oversized—firetube boilers.  The following year, they added another 100 HP water-tube system and, within a few years, they verified 30 to 40 percent annual fuel savings. I could reel-off countless instances where water-tube boilers have exceeded expectation.”

Water-tube systems are designed to work with high-ash fuels that, when combined with soot blowers, typically meet environmental regulations. This also means that they’re well-suited for biomass applications and waste-to-energy plants.

The primary factor that determines heat transfer is the heat transfer coefficient, based on the transfer fluid’s flow pattern, characteristics and chemistry (including density, conductivity and viscosity), geometry of the flow passage, and surface conditions. Of these factors, the most important to thermal efficiency in a water-tube boiler is flow through the water tubes and the fluid’s velocity and density. When all of these variables are optimal, water-tube boilers provide exceptionally reliable operation, while offering performance and efficiency that is difficult to match with any other heat exchanger design.

For these and other reasons, water-tube boilers are the equipment of choice for many industrial process applications. Their ability—in a steam boiler configuration—to handle greater pressures and very high temperatures provides superior steam generation in the millions of pounds/hr.

Caveats

Most advantages come with a counterbalance; water-tube boilers are no exception.

The initial cost for a water-tube boiler is usually higher than that of a fire-tube boiler of similar capacity. And, depending on size, some water-tube boilers can be assembled on site, which can add to the cost and the time required for installation.

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Bryan’s RV600 flexible water-tube steam boilers are a great fit for many commercial heat or process steam application. The systems offer 3,500,000 to 8,000,000 BTUH with forced-draft gas, oil or dual fuel. Image courtesy of Bryan Boilers.

By design, the concern of heat transfer fouling—typically in the form of accumulated mineral scale—is heightened. For that reason, fill-water quality and the steady monitoring and maintenance of water chemistry are essential to peak operation.

The accumulation of scale is by no means specific only to the water-tube design.  Scale can accumulate faster because of the water-tube boiler’s lower water mass, but it’s still a concern across all heat exchanger types. “But, reduced water volume also equates to savings on chemical treatment,” added Blackwell.

Finally, the reduced volume of water affects the water-tube boiler’s ability to meet the call for sudden changes in heat demand. This shortcoming is often remedied by the addition of an indirect water storage tank.

Fire-tube advantages

Advantages include their simple construction and the ability to easily meet rapid fluctuations in the need for heat. As a lower cost alternative to water-tube boilers, they’re often used for smaller commercial or industrial facilities with lower operating pressures.

Fire-tube boilers are designed with water in the unit’s main vessel, achieving higher mass. Because of their higher water volume, system design also offers the benefit of a less urgent need to maintain tight control of water quality. If water quality deteriorates and isn’t corrected quickly, there’s less chance— when compared to water-tube technology—that system performance will be affected.

Another advantage to fire-tube boilers may be lower upfront cost. “However, said Blackwell, “In our market, there’s very little, if any, difference in pricing.”

Caveats

A fire-tube boiler’s higher water volume and lower flow rates also mean that they may offer less efficient heat transfer. Likewise, the greater water volume requires a longer wait for system start-up, and may also challenge the boiler’s ability to meet demand for constant water flow—and heat transfer—at peak conditions.  Standby losses are greater because of the boiler’s higher volume of water.

 

The main disadvantage of fire-tube boilers is that they tend to have smaller capacities and can’t handle internal pressures over 250 psig (the steam capacity range of fire-tube steam boilers is approximately 5,000 to 75,000 pounds/hr.)  Or, if configured as a hot water boiler, hot water capacity is between 2 million to 100 million BTUs.

Traditional, horizontal fire-tube steam boilers may offer a capacity as low as 690 pph—pounds (of steam) per hour. Traditional fire-tube steam boilers in a vertical configuration will go  smaller—offering  as little as 207 pph, for example.

Boiler Safety—be warned

Operationally, water-tube boilers are known to be safer than fire-tube systems.  This is because of the much greater volume of water held within fire-tube boilers—containing as much as 10 times the volume of a water-tube boiler of similar capacity.

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Burnham Commercial Boilers offers a convenient solution with efficient, easily portable, mobile boilers. Image courtesy of Burnham Commercial Boilers

When fire-tube boilers are inadvertently operated with low water volume, very dangerous risks can develop.  Initially, the metal in the boiler warps and contracts. Then, if cold fill-water enters the boiler in a hot, low-water condition, the metal could rapidly expand, causing an explosion.

Should a similar scenario take place in a water-tube boiler with lower internal water volume, an explosion would be much less severe. In most instances— should fill-water enter a hot water-tube boiler with an insufficient fluid level— conditions would likely lead to metal fatigue, a crack, and leakage.

Service and maintenance

Some boiler designs are built to facilitate ease of service and maintenance. The assumption, however, is that a newly-installed boiler is ready for the rigors of duty, 24-7-365. Yet, all mechanical equipment is not created equal. Service and maintenance work ideally happens systematically to maintain optimal performance and efficiency—not to deal with challenges that arise as a result of faulty or compromised design.

Commercial boilers should be designed to ensure long-term durability and optimal performance. Ideally, the burner is mounted front and center, fully accessible and serviceable. Removable panels around the boiler should provide access to the burner chamber and entire heat exchanger. There should be no need to disconnect blowers or gas piping.

Commercial Condensing Systems 

As with all technology, improvements emerge to enhance operation, durability or efficiency. The emergence of condensing capability—often going hand-in-hand with “turn-down” (or  modulation, offering very efficient, partial firing)— are the most substantial enrichments to boiler systems in decades.

Condensing boilers are based on a remarkably simple concept. They achieve higher efficiencies by condensing the flue gasses. In contrast—in a conventional boiler, latent heat contained in the flue gas escapes through the flue vent. They’re also quite effective at reducing NOx, COx and other harmful emissions.

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Burnham Commercial Boilers offers a convenient solution with efficient, easily portable, mobile boilers. Image courtesy of Burnham Commercial Boilers

Modulating condensing boilers (AKA “mod-con” boilers) earned “greatest achievement” recognition as a result of their dramatic contribution—pushing fuel efficiency from 80 percent for non-condensing boilers, and up into the 90+ percent range for mod-con systems. Condensing water-tube boilers achieve efficiencies of up to 98 percent, higher than most condensing fire-tube systems—a result of their better heat transfer. With modulation, they provide a range of firing rates to match the variable heating load of the building.

However, mod-con boiler efficiency depends on the temperature of the water returning to the boiler. The lower the return water temperature, the higher the efficiency. Low boiler return water temperature depends on the overall boiler system design, not just the boiler.

Condensing boilers cost  40 to 50 percent more, on average, than conventional systems. However, the difference in cost is typically recovered in four months to four years, depending on a wide range of variables. Substantial cost-saving incentives may apply.After the initial cost recovery period, the fuel savings are quite significant over the life of the boiler.

There are a few disadvantages. For instance, one fire-tube boiler design change involved the arrangement of internal tubing from a horizontal format, to vertical. The revision was warmly welcomed by facility owners and installers alike because their now-smaller size permitted movement through a standard door frame. As a result, the products of combustion and condensate were redirected: rather than gradually absorbing heat as flue gas passes through tubes, the contemporary vertical fire-tube burner sits inches away, forcing heat directly on the tube sheet, welds, and tube tops. All materials expand and contract as they’re heated and cooled, and these internal components  of the vertical fire-tube boiler are no exception. The design tends to concentrate too much heat on metal components.

Cleanings and reparability

If a condensing boiler’s panels are easily removed, providing complete access to the entire heat exchanger, byproducts of combustion can be easily removed with a service brush. This is an important facet to maintaining a boiler’s original high-efficiency rating.

water-tube boilers, boilers, hydronics, fire-tube boilers, Burnham Boilers, Bryan Boilers, Thermal Solutions Boilers, AMP water-tube boilers

A Thermal Solutions AMP water-tube boiler is rated at 97% efficient. The stainless steel, modulating-condensing boiler line offers a size range of 1,000-4,000 MBH.

Should repair work be required, all components of the heat exchanger should be easily accessible for service or replacement—including even the possibility of changing one or more internal tubes in the field.

With properly isolated equipment, service work could and should be completed within hours, not days or weeks.

Systems that offer the greatest resistance to cleaning are those with tight, top access and—when opened—may have many welded tubes. Those that do typically require entirely new heat exchangers, sometimes costing as much as 60 percent of the original install.

Knockdown rewards

Knockdown condensing boilers were, for good reason, greeted enthusiastically by the commercial market. Some of these systems use no welds in securing tubing to the header.

The “knockdown” moniker stems from the ability to assemble or disassemble a boiler of any size with relative ease and precise repeatability. The systems arrive on jobsites, similar to old cast iron sectional boilers, or partially assembled based on space requirements.

Even elevator weight constraints pose no challenge to getting the boilers in place. If there’s a need to maximize mechanical room space, some systems are available with reverse construction models to optimize clearance space between units or to be placed side by side, to be serviced from outside.

Greg Hughes is the Internal Sales Manager, Thermal Solutions and Burnham Commercial. He can be reached at ghughes@heatingsolutionssales.com

 

Additional sources:

Jim Knauss – jknauss@burnhamcommercial.com   (retired but now consulting) Engineer for Burnham Commercial (firetube merits)

Joe Tinney – jtinney@heatingsolutionssales.com Internal Sales Manager for Bryan Boilers (watertube merits)

Rick Constantino (rconstantino@bresales.com) – Owner/COO Boileroom Equipment Company

Theodore (Ted) Dreyer (TDreyer@WHGardiner.com) – Sales for Gardiner

We visit the newly-built Martin Softball campus on the campus of the University of Illinois, Urbana-Champaign to talk with Chris Asklund, project manager for A&R Mechanical, about the heating component of the project and its reliance of NIBCO butterfly and ball valves, and strainers. The new state-of-the-art indoor practice facility for the Fighting Illini softball Read more

We visit the newly-built Martin Softball campus on the campus of the University of Illinois, Urbana-Champaign to talk with Chris Asklund, project manager for A&R Mechanical, about the heating component of the project and its reliance of NIBCO butterfly and ball valves, and strainers.

The new state-of-the-art indoor practice facility for the Fighting Illini softball program was built thanks to a sizable lead naming gift from Rex Martin and his daughters, Ashley Martin and Alexis Martin-Klose. Their gift will honor their late wife and mother, Alice Martin.

Welcome to another edition of our Hub Spotlight series where do a deep dive into the men and women who make the trades great. This spotlighted tradesperson tells us that he really enjoys trashy reality TV. “Nothing like kicking your feet up and watching someone making horrible life decisions on 90-Day Fiancé on a Sunday Read more

Welcome to another edition of our Hub Spotlight series where do a deep dive into the men and women who make the trades great. This spotlighted tradesperson tells us that he really enjoys trashy reality TV. “Nothing like kicking your feet up and watching someone making horrible life decisions on 90-Day Fiancé on a Sunday evening.” Joking aside, for Keith McGillivary (@mps_207)—full-time business owner of McGillivary’s Plumbing Services (MPS), Gardiner, Maine, for the past two years—his story into the plumbing trades is an interesting one.

Keith McGillivary, MPS Plumbing Services, plumbing, heating, piping, HVAC, trades, Hub Spotlight, skilled trades

McGilivary’s path started in a small town when a small plumbing business was looking for a helper, and he was looking for a job. “Little did I know it would be the start of where I am now,” says McGillivary. Before college, McGillivary started working for a small plumbing business that primarily focused on service work. The owner, Russell, was/is a great mentor and really took the time to help him understand not only what they were doing, but why they were doing it.

Keith McGillivary, MPS Plumbing Services, plumbing, heating, piping, HVAC, trades, Hub Spotlight, skilled tradesAfter deciding to pursue plumbing, McGillivary attended Southern Maine Community College (SMCC) for its plumbing and heating program. Through college, he continued to work alongside his mentor, and after graduation, continued to work for him full time for three years. McGillivary then took a job at Bath Iron Works (BIW) as a pipefitter building destroyers, ships for the United States Navy. “The piping systems were complex, and although it was “plumbing on a ship,” it was completely different. I found it fun to learn the ins and outs of that particular plumbing,” says McGillivary.

Eventually, McGillivary joined the Pipefitter Test Crew and tested the piping systems after they were built. He worked there for six years, but the whole time he continued to work nights and weekends doing plumbing work on the side. “This allowed me to gain hours and knowledge for my Master’s test. After passing my Masters, I decided to make the plunge into self-employment because I wanted the schedule flexibility for my family,” says McGillivary.

Keith McGillivary, MPS Plumbing Services, plumbing, heating, piping, HVAC, trades, Hub Spotlight, skilled tradesIn fact, McGillivary’s biggest motivation for self-employment was time, rather than money. “I have learned to set firm boundaries for myself when scheduling and taking on jobs. I have been able to take more time off for my family than ever. Being a service plumber, in this day in age, you could work 24/7 if you wanted. I try to work ‘normal’ hours, and if I can take a day off for family stuff, I always do,” says McGillivary.

Shout Out to Mentorship

Keith McGillivary, MPS Plumbing Services, plumbing, heating, piping, HVAC, trades, Hub Spotlight, skilled tradesAccording to McGillivary, Russell taught him everything he knows about plumbing and owning a business. “He taught me all the hands-on work, how to write estimates & bid on jobs, customer relations, and how to balance a small business/family life,” says McGillivary.

And McGillivary wants to pay it forward. “I definitely consider myself a role model for others looking to join the trade. I feel I am a good example that hard work and dedication pays off,” says McGillivary. “My mentor was so important to my journey that I try to give back what I can by being transparent about my plumbing knowledge.”

Uplifting the Trades

Recently, there has been a big push for kids to attend trade school so there has been a shift in younger people showing interest, says McGillivary. “Trade school was beneficial for me to learn the code side of things, in an environment different from the hands-on work. I think we could get more interest in the trades if the schools showcased all the different avenues someone could go once they completed their schooling, and the financial opportunities that come with them. Everyone expects a doctor to make six figures, but not everyone knows you can make that in the trades without massive student loan debt,” says McGillivary.

“Everyone expects a doctor to make six figures, but not everyone knows you can make that in the trades without massive student loan debt.”

Social media can also be used to attract more people to the trades. “I see it all too often when guys in the trade are way too harsh on people for asking questions on Facebook plumbing pages. There are so many people asking questions for the purpose of learning and gaining knowledge. We were all there at some point, so be kind enough to answer the questions in a helpful manner. Social media can also be used to form “new-to-the-trades” communities and to provide seminars,” says McGillivary.

Keith McGillivary, MPS Plumbing Services, plumbing, heating, piping, HVAC, trades, Hub Spotlight, skilled tradesSocial media also has played a huge role in the growth of McGillivary’s business. Starting as a small, part-time business with the help of word-of-mouth recommendations on small town Facebook pages, which made McGillivary realize that social media could be used to showcase the work he is doing on a day-to-day basis. “I use my Instagram to show what I am about as a business and the work I put out. I have found that if a customer can see why you are more expensive than the other guy, then they are more likely to go with you. I use it as an open-door insight to my business both in reels and daily stories,” says McGillivary.

McGillivary uses social media to learn little tricks of the trade that he just wouldn’t have been exposed to, being from such a small town. For McGillivary, it is extremely beneficial to be able to have conversations with such great tradesmen. He also talks to apprentices daily or weekly about projects, and gives them advice. “I wish when I was learning, I had this platform to learn and meet others. As visual learners, much like a lot of trades guys I know, it’s changed the way we can learn,” says McGillivary.

Making Time

Summers in Maine are short, so McGillivary tries to spend every nice weekend camping in his camper. In the winter months you can find him on his snowmobile at camp. “I would love to ride my snowmobile from camp in northern Maine to the Gaspe Peninsula to complete the “Great Gaspe Snowmobile Tour,” a six-day, 1,500-mile ride around some of the best trails,” says McGillivary.

Keith McGillivary, MPS Plumbing Services, plumbing, heating, piping, HVAC, trades, Hub Spotlight, skilled trades

And the last day McGillivary said it was a great day? “You know it’s funny, as I look back on just yesterday—camping with my family, beautiful weather, everyone smiling, does it get much better than that? So, the answer to that question would be yesterday!”

Go-To Tools on the Job

According to McGillivary, his go-tools are a couple pairs of Knipex Cobra pump pliers, a 6-in-1 screwdriver, and an adjustable wrench. Any good service plumber can fix most things with those!

Also, I find myself feeling naked if I don’t have my Leatherman Wave on me. Another great tool that has many uses.

Lastly, if there was one tool that changed the service plumbing game, it’s the M12 Milwaukee press tool. If you’re running a service company and don’t have one, you’re late to the party.

 

The word separation was being used in hydronic circles back when I started in the business. Of course, I am old, so there is that. Many manufacturers and trainers are in the separation bandwagon now, rightfully so, from my view. Let’s take a look of how the word and the technology come together. The action Read more

The word separation was being used in hydronic circles back when I started in the business. Of course, I am old, so there is that. Many manufacturers and trainers are in the separation bandwagon now, rightfully so, from my view. Let’s take a look of how the word and the technology come together. The action of moving of being moved apart will work to describe the value of separation in hydronics or piping systems in general.

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Photo: Bayshore House (Newport Beach, CA) Submitted by: David Mayo

Back in the day, we used a device called an air purger. We’ve all seen them, sometimes described as a camel hump. Commonly made from a casting, the “air purger” basically builds a wide spot in the road. As such, as fluid flows through it, the speed or velocity slows. Slowing the fluid allows air to rise up to the top of the “hump” to be vented away. It can, and does, some air removal in a system. A few important details. It likes to have some straight piping upstream, maybe 18” or so. This helps get the air going to where it can best be removed, at the top of the piping.

The velocity or speed is also critical. Water or fluids, flowing above 4 fps feet per second, tend to blow through the camel hump like bad leaves in the desert. Lastly, they have a tougher go grabbing the micro bubbles. If you fill a glass at the kitchen sink and notice cloudy water at first, those are micro bubbles. In your glass, since the top is open, this air escapes. It escapes quickly as the pressure has been taken off the fluid form when it was captive in the piping under 60 psi, or some pressure.

Some smart fellow decided there must be a better way to rid 95% or more of all air out of a closed loop piping system. The wide spot in the road had validity. Why not put something inside that wide spot to aid the collection. The microbubble resorber was born. The “stuff” in the chamber becomes a coalescing media. Simply the air bubbles, of all sizes cling to the media inside instead of blowing through like grass through a goose.

The concept works amazing well. Air can be successfully removed in a matter of minutes or hours on larger systems as it passes across the coalescing media. The microbubbles that were present in systems with camel humps, now have been captured and removed.

Why all of a sudden is this so “in Vogue”? High efficiency boilers are one great reason to use microbubblers. The fluid content is way down, the HX metals are much thinner, and the flame is in close proximity to the boiler wall. As such, any layer of micro bubbles stuck on the metal surfaces reduce or impede the energy from the flame getting to the fluid. You have a miniature bubble wrap layer around the boiler surfaces if you are not getting the small air gone.

You may have seen failed mod con boilers. Darkened, brown or black metal instead of shiny stainless or aluminum. That HX has been overheated. Often lack of flow is to blame. And also, often the lack of flow is related to air bubbles slowing or stopping the perfect contract between fluid and hot metal surface. You take an efficiency hit also when you have this going on in your boilers. Circulators, the wet rotor type, especially like to be free of air, both from a performance and lubrication standpoint.

So, doesn’t it make sense that the same phenomena happen in your heat emitters? Microbubble air layers in your radiators, fin tube, air handler coil, coil in your indirect tanks.

hydronics, boilers, separation, air separator, magnetic separator, dirt separator, plumbing, heating

Telluride Custom Home (Telluride, CO) Submitted by: Pete Cassidy

The microbubble resorbers aka air separators bring a few other advantages. They do not require straight piping upstream to work efficiently. This can be a big asset when you need to cram 10 lbs. of potatoes in a 1-pound sack, i.e., small mechanical closets. They are not as sensitive to over-pumped conditions, high velocities above 4 fps for example. The large chamber combined with the media inside work together to grab bubbles from speeding fluids. They are brass or composite construction, so corrosion issues are mitigated. Ever see a camel hump with the air vent port rusted close when you pull the 1/8 auto vent off the top? It was handicapped from first installation; the plugged vent hole renders it a “boat anchor.”

Yeah, I know they cost more than a chunk of iron than your great grandfather used his entire career, but times have change, my friends. Why not give your customers a system with the very best equipment and conditions to be highly efficienct. A simple device that removes 95% of air in systems almost instantly is what you need to consider.

So, you took my suggestion and STILL have an air/ noisy system. Now what? Look for places where air is getting in. Yes, air can enter a closed loop system, even a pressurized one. Those float type auto air vents allow air to move in both directions, in and out. IF one were to be installed in a point in the system that sees sub-atmospheric conditions you are seeping air into the loop. The most common occurrence is when you have the expansion tank misplaced. This can get worse with high heads circulators creating large pressure differential. The tank MUST be on or near the suction side of the circulator(s) to avoid pulling a vacuum in your system. Make it right or cap off auto vents in the negative pressure part of the system.

By Aaron Stotko When a century-old Dallas railroad company headquarters required major renovations to transform into a Homewood Suites by Hilton, initial cost estimates for the hydronic heating system came in too high. That’s when City Wide Mechanical of Dallas looked to alternative piping systems for a solution. They found PEX-a pipe with F1960 expansion Read more

By Aaron Stotko

When a century-old Dallas railroad company headquarters required major renovations to transform into a Homewood Suites by Hilton, initial cost estimates for the hydronic heating system came in too high.

That’s when City Wide Mechanical of Dallas looked to alternative piping systems for a solution. They found PEX-a pipe with F1960 expansion connections to be the ideal system, due to its durability and ease of installation in addition to the job-site productivity, safety and, best of all, profitability potential it provided.

PEX-a pipe, Uponor, Uponor PEX, Aaron Stotko, plumbing, piping, hydronics, pipe joining, PVF, HVAC

And City Wide Mechanical isn’t alone in their findings. Many mechanical contractors are discovering the benefits of PEX-a pipe and F1960 connections as the preferred alternative to copper, iron, and steel, which have dominated the mechanical piping industry for decades.

Benefits of PEX-a

PEX is an acronym for crosslinked polyethylene. It has been used in North America since the mid-1980s, starting with radiant floor heating systems, then moving into plumbing and, eventually, to hydronic hot-water heating and chilled-water applications.

PEX can be manufactured via three different processes, which create products with varying crosslinking percentages that allow for different characteristics. PEX-a is the most durable, flexible, and resilient with crosslinking around 85%. PEX-b is a stiffer piping product with crosslinking around 65% to 70%, and PEX-c features crosslinking around 70% to 75%.

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ASHRAE Headquarters Grand Opening Fall 2021, photos by Devin Abellon

One major benefit of the higher crosslinking in PEX-a is its extreme flexibility along with its thermal and shape memory. The flexibility of PEX-a eliminates most connections in smaller-diameter piping, saving time and money with up to half the connections required in rigid metal piping systems. To make a change in direction, the installer simply bends the pipe instead of having to stop and make a fitting. There are also bend supports available that help hold a bend securely in place.

The thermal memory of PEX-a provides kink repairability with a simple shot of heat from a heat gun. This eliminates the need to add in a coupling if a kink ever occurs in the pipe. (It is important to note that kink repairability is not possible with PEX-b or PEX-c pipe.)

The shape memory of PEX-a allows the pipe to expand and contract back down to its original shape. This makes it extremely resilient in freezing conditions and also provides for the fastest, easiest, most reliable PEX-a fitting system — F1960 expansions.

PEX-a pipe, Uponor, Uponor PEX, Aaron Stotko, plumbing, piping, hydronics, pipe joining, PVF, HVAC

Expansion fittings require one simple tool to expand the pipe and an expansion ring before inserting a fitting. As the pipe and expansion ring naturally shrink back to their original shape, it creates a strong, durable connection that holds tight and can never be dry-fit. (Note: It is not recommended to expand PEX-b or PEX-c pipe due to microcracking that can occur.)

The innovative expansion fitting method eliminates torches, glues, and solder from a job site for greater worker safety. Plus, the system is extremely easy for installers to learn, helping get new crews up to speed quickly.

Speaking of job-site safety, PEX is also much lighter in weight compared with metal systems. For example, a 300-foot coil of 1/2-inch PEX weighs about 18 pounds, whereas the same amount of copper pipe weighs around 85 pounds. The lighter weight of PEX makes it safer and easier for installers to move around a job site and also eliminates the need for heavy-lifting equipment.

PEX-a also has a long-term advantage over copper when it comes to performance longevity. It is a static system, meaning its internal surfaces — which are three times smoother than copper — will not pit, scale, or corrode. That means its performance will remain the same from day one through decades of use.

Finally, because it is not a traded commodity, PEX-a holds a relatively stable material cost. This makes bidding a project much more consistent and reliable.

Application Details and Installation Tips

PEX-a is regulated by the ASTM F876 standard, which denotes temperature and pressure ratings of 200°F at 80 psi (pounds per square inch), 180°F at 100 psi, and 73.4°F at 160 psi. These values are well within the range of operation for most hydronic systems, including chilled beams, fan coil units, baseboards, radiators, hydronic VAV (variable-air volume) reheat coils, and radiant manifolds.

Because PEX is oxygen-permeable, it is important to use a pipe with an oxygen barrier that limits oxygen diffusion to levels below DIN 4726. This will protect the metallic components in the mechanical piping system, such as valves, strainers, and pump volutes, from corrosion.

The pipe is manufactured in sizes from 5/16 inch up to 4 inches and features a copper tube size (CTS) outside diameter. This means all the off-the-shelf components used in a copper hydronic piping system — hangers, supports, and insulation — can be the same.

PEX-a pipe, Uponor, Uponor PEX, Aaron Stotko, plumbing, piping, hydronics, pipe joining, PVF, HVAC

For horizontal piping, the industry offers PEX-a Pipe Support — a galvanized-steel channel that is 9 feet in length and available in PEX pipe sizes from ½ inch to 3½ inches. This solution enables hanger spacing similar to copper pipe and helps control the natural expansion and contraction of the pipe as it heats and cools.

Because PEX-a expands at 1.1 inches per 100 feet per 10°F Delta T (which is 10 times that of copper), installing anchors every 65 feet and using PEX-a Pipe Supports allows PEX-a to function much like a copper system. In fact, different installation methods have a different effect on the overall net expansion rate.

With a strut-and-clamp system, using PEX-a Pipe Supports and anchoring with fixed points reduces the expansion rate of PEX-a to 0.08 inches per 100 feet per 10°F Delta T (a rate less than copper). And a loop-and-clevis system can reduce the rate to 0.12 inches per 100 feet per 10°F Delta T.

If you’d like to learn more about PEX-a piping systems, visit the Plastics Pipe Institute at plasticpipe.org or the Plastic Pipe and Fittings Association at ppfahome.org.

PEX-a pipe, Uponor, Uponor PEX, Aaron Stotko, plumbing, piping, hydronics, pipe joining, PVF, HVACAaron Stotko is the director of Segment Marketing at Uponor. He can be reached at aaron.stotko@uponor.com.