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Condensing Boilers Get An A+

When it comes to measuring the efficiency of a boiler, every engineer knows that if you put one Therm of natural gas into a boiler and you get 100,000 Btu’s of heat in the steam coming out of that boiler, you are achieving 100 percent efficiency. And, as any engineer can tell you, achieving that state of efficiency in boilers is something that simply can never be done.

Or can it?

While the efficiency of commercial boilers will vary depending upon factors such as the type of fuel, geographic location and other variables, as a rule of thumb it was generally believed that if you were achieving 80% efficiency from your boiler, you were being pretty efficient. But a new type of boiler is entering upon the commercial scene in the U.S. that is reported to be producing efficiencies nearing 95 percent!

These new type of boilers are called “condensing” boilers and while they are relatively new in the U.S., they have been around for years in Europe, where the cost of energy and a strong, green initiative have made these boilers popular in both residential and commercial applications. Now that those high fuel costs have come to the U.S., these boilers are finally finding a market here with both commercial and residential building.

I suppose the easiest way to explain the difference between a condensing boiler and a conventional steam or hot water boiler would come if I had the ability to put your hand on the flue stacks coming from these different boilers. If you touched the stack from a conventional boiler, you could wind up with a 3rd degree burn in an instant. That’s because the boiler is expelling a great deal of heat through the stack and into the atmosphere. With the condensing boiler, however, you might have difficulty feeling any temperature differential in the exhaust stack because the temperature of the boiler exhaust is near to room temperature.

As every engineering trainee learns, in a traditional boiler it is important to keep the exhaust gas temperature high enough to avoid condensing those gases in the flue or chimney. As the gases of combustion condense, they can form hydrochloric acid, sulfuric acid and even trace elements of benzene (depending on fuel types). These gases will corrode boiler tubes, plates, masonry and refractory. This is one major reason why all that wasted energy is going out the boiler flue and up that stack. Condensing boilers are designed using stainless steel and corrosion resistant parts that can withstand the formation of these corrosives.

Why wasn’t this done before? Well, the cost of making a boiler using expensive materials such as stainless steel just didn’t make economic sense before. Today, however, two things have changed all that and made condensing boilers very smart indeed. First, the cost of fuel has skyrocketed and continues to climb in price, making the additional investment in higher efficiency boilers a smart investment with a rapid return. Secondly, the design of some new condensing boilers has allowed for increases in efficiency along with reduction in size. Traditional boilers that may have had 30 to 50 gallons of water circulating inside of them are being replaced with condensing boilers that have less than one gallon of water circulating in a tightly closed system.

But of course, all this is what manufacturers are saying and various distributors report at their sites on the Internet. The question we had, and, more importantly, our readers had, was “do these new condensing boilers really live up to all the hype”? And to answer that question, the Chief Engineer hooked up with Bill Bailey, the Hydronic Manager of Temperature Equipment Corporation in Lansing, Illinois. TEC is the equipment representative for the Munchkin brand of condensing boilers and Bill was eager to highlight the success stories he has been accumulating from this new type of boiler in various commercial applications.

We told Bill we were interested in verifying the savings and efficiencies of these boilers so he invited us to travel to Highland, Indiana to look at several locations where these boilers have been installed and measurable savings have been obtained and documented.

Our first stop in Highland was at Siemer Heating & Cooling where owner George Siemer, a customer of Bill’s, greeted us. George has been installing and servicing HVAC equipment in the northern Indiana area since the 1970s, and it was clear from the beginning of our conversation that he views energy conservation as more than just a smart business strategy but as an environmental imperative as well. George was more than happy to talk with us about condensing boilers and agreed to take us to some locations where he installed condensing boilers and documented the energy saving results.

Our first stop would be Highland Christian Academy serving grades K through 12. The school was in the process of expanding and George’s company had replaced the large traditional cast iron steam boilers with stage fired condensing boilers and had converted the hot water heating system to accommodate individual control at each classroom or in zoned areas such as the gymnasium.

Along the way to our first stop, I had time to look at some of the manufacturer’s literature for Munchkin boilers and was pleased to learn that while the technology was developed in Europe, the boilers are manufactured right here in the USA.

I also learned that the boilers come equipped with modulating burners that control the rate of burn in proportion to demand. The boilers can operate on direct zone control or can be tied to outdoor sensors that reset the boiler setpoint based upon outside temperature.

While all these control schemes are available on conventional boilers, what amazed me was the small size and full control features available on such a compact boiler. I also took note that these boilers can be tied in through heat exchangers to furnish all domestic hot water service as well as heating.

When it came to exhaust gas from these boilers, the literature stated that exhaust temperatures from the boiler would be so low that standard schedule 40 PVC pipe could be used for exhaust venting. Without the need to place boilers near existing chimneys, both homeowners and commercial property owners would be given a lot more flexibility on where they could put these boilers, allowing them a lot more freedom in their space planning.

According to some of the literature I was reading, a 3-year energy cost comparison showed that modulating condensing boilers could result in a whopping 50% savings in energy costs compared to conventional boilers. With natural gas prices rising steadily, this sudden jump in efficiency with a typical ROI of around three years was starting to make me envious of the folks who never made the jump to forced air HVAC.

We arrived at the school in the midst of a flurry of activity. The summer recess was drawing to a close and classes would resume in the following week. Teachers were busy preparing their classrooms and custodians were active throughout the school, polishing floors and getting things ready for the hundreds of students that would fill the classrooms in the coming week.

We made our way to what was clearly the old boiler room of the school but nothing in the room looked like the typical boiler rooms we have come to expect. In place of old cast iron boilers were three very small devices that you would be hard-pressed to identify as boilers unless someone told you so. The smart looking boilers stand about 3 feet off the floor, and while they were not in operation while I was there, I have been told their noise level is insignificant.

George explained to us how Siemer had been contracted to cut out the old cast iron boilers and remove them and install the stage-fired Munchkins. He explained how they had taken advantage of an existing steam tunnel to run new copper piping and PEX tubing to individual zones and heating units, permitting teachers and staff to have local control over the temperatures in their classrooms for the first time. As he spoke, I was reminded of my own school years and the cast iron radiators spotted with melted crayons and regulated by opening and closing windows in the classroom, even on subzero days.

According to Bill, the only problem he has encountered with condensing boilers thus far has come from installation. “It’s not that hard to make a piping error,” he said. “Installers have to learn that condensing boilers are different and they have to be piped differently than conventional boilers.” Bill told us that other than piping in the boilers wrong, he hasn’t found a single problem or heard of a single complaint with condensing boilers.

We continued our tour of the school and George showed us how he re-configured existing air handling units in classrooms, installing new coil units and individual controls. We then went outside and were amazed to see the boiler exhaust terminating flush with the exterior of the building, well above the snow line but without any need for elevation.

Each boiler comes with a combustion air fan and no natural draft is needed for firing. When we looked, sure enough, schedule 40 PVC had been used for exhaust.

George was anxious to show us another installation nearby that he had completed earlier for a church. This time we pulled into the parking lot of the First United Methodist church and went into a neat boiler room that had also been configured with stage-fired Munchkin condensing boilers. As we looked over the installation, we noted that the compact size of the boilers allows for easy repair and replacement of circulating pumps and valves. From an engineer’s perspective, one of the best things about these compact boilers is the fact that every boiler room can end up gaining space following conversion to these compact little powerhouses.

An interesting side note I picked up on was the fact that George had guaranteed the energy savings from these boilers as part of his winning bid to get the job. That told me that these condensing boilers clearly brought home the savings.

We had begun our journey into Indiana to answer the question for our readers of how well condensing boilers seemed to be living up to their hype in the commercial market. What we learned can be summarized in two key points. First, condensing boilers have a unique method of piping that is significantly different from conventional boilers. Therefore, it is critical that installers are trained in the piping plan unique to these types of boilers. Secondly, we found that condensing boilers are the future. There is no doubt that they provide the saving not only in energy, but in the accommodating manner that they are installed which saves room and affords flexible control schemes that would accommodate any small to medium-sized commercial application.

We thanked George Siemer and the folks at Siemer Heating and Cooling for graciously agreeing to give us a tour and show us the great installation projects his company has done. You can find out more about Siemer heating and cooling at their website, www.siemerinc.com. And we thank Bill Bailey of Temperature Equipment Corporation for showing us the unique features of Munchkin brand condensing boilers. Readers who are interested in learning more about these boilers can contact Bill at 708-418-0900 or check out the TEC website at www.tecmungo.com.

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