By Robert Wiseman
From the December 2018 Issue
Considering the fact that the thermostat wasn’t invented until 1883, the pace of change in heating technology has been nothing short of astonishing. In this article, we’ll explore some of the most noteworthy recent breakthroughs in boiler technology.
Efficiency keeps rising. It’s now possible to get more than 96% thermal efficiency in boiler sizes up to 6 million BTU/hr. Some condensing boiler products deliver this high efficiency with minimum supply gas pressure as low as four inches water column. Negative regulation technology draws gas into a pre-mix combustion system instead of relying on utility pressure through the gas valve. Plus neg/reg fan control fine-tunes the fuel/air ratio entering the burner, providing a cleaner burning flame that achieves high combustion efficiency.
Installation getting easier and less expensive. Fifty years ago, most commercial boilers were so large and clunky that they had to be sawed apart to be removed from a building when their working days were over. Today, boilers have a much leaner design, yet they’re a lot more durable.
It’s the innovations inside that are making boiler installation easier and less costly. Recent breakthroughs in variable flow technology are significantly reducing boiler installation costs. Some high-end condensing boilers can operate over a wide range of flow rates with very low pressure drop. This makes it possible to install a full flow (variable primary) system. This streamlines installation by eliminating the time and materials cost of primary/secondary (boiler/system) piping—or the need for pumps to maintain flow. Variable flow technology also makes these boilers more flexible in handling frequent fluctuations in system flow rate.
Advances in fire-tube heat exchangers. Today’s most innovative fire-tube designs enhance the life of the heat exchanger by allowing the tubes to flex. This lets them operate stress-free—without the adverse effects seen in earlier generations of fire-tube heat exchangers.
When each fire tube is welded into the heat exchanger and surrounded by water, the heat transfer process is enhanced by the water’s counterflow motion. As water flows up inside the vessel, super-heated flue products flow down the fire tube. With just one pass, heat is effectively transferred, thereby reaching condensing temperatures. At the top of the vessel, the combustion chamber is also water-backed for additional heat transfer.
Smoother, quieter modulating combustion. Boilers using advanced fire-tube technology deliver smoother, quieter combustion with up to 25:1 turndown. For example, a boiler can fire at its maximum of 2 million BTU/hr rate when the heat load is highest, then gradually turn down as low as 4% (80,000 BTU/hr) as load decreases.
A modulating boiler system runs very efficiently, without frequent on/off cycling. When the system is zoned, units with high turndown rapidly work to match the actual system demand. This lowers a building’s fuel bill and provides better comfort by load-matching the heat loss of the system.
Ensuring greater uptime. Today’s most innovative boiler systems are designed to deliver reliable performance with virtually no downtime. They accomplish this by sequencing multiple boilers together so there is cascade redundancy if one unit is turned off for maintenance. For example, if the lead boiler is being serviced, cascade redundancy automatically shifts the lead role to the second sequenced boiler.
Cascade sequencing can be programmed for two types of operation: lead-lag and optimization:
- With lead-lag operation, one lead boiler modulates to capacity on demand. As load increases, the system then cascades to additional lag boilers in sequence. The first-on role can shift daily, distributing equal runtimes to each boiler.
- In an optimized system, all boilers fire and modulate simultaneously at the same BTU/hr input rates, maximizing thermal efficiency.
A revolution in connectivity. The first generation of building automation system (BAS) configurations usually required a standalone mid-range computer like the IBM AS/400 to control the boilers in just one building. Now facility management have the ability to monitor and manage multiple boilers across geographic locations using an app. The key is to integrate boiler operating controls effectively with a remote connectivity app. This allows one person to manage multiple boiler plants across different time zones and locations. Once the app is loaded onto an iPhone or other smart device, the user receives a text any time there’s a change in system status. It’s now easier than ever to integrate remote connectivity tools into a BAS using Modbus and BACnet MSTP as standard equipment.
Today, facility executives are exploring Internet of Things (IoT) technology. These include innovations like “smart” lighting, and boiler manufacturers are also starting to design IoT solutions. Networked boiler plants are now serving many of the world’s leading company headquarters—and even their satellite offices around the globe. These sophisticated systems are helping reduce facility heating costs and improve performance even further.
Wiseman is commercial boiler product manager at Lochinvar, LLC, a developer and manufacturer of high-efficiency water heating products. The company is headquartered in Lebanon, TN.
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