High-efficiency boilers are changing commercial heating

With condensing technology, modulating consumption, and even built-in redundancy, the latest generation of commercial propane space heating and water heating systems offers a leap forward.

By Jeffrey Lee

PERC Staff Writer

Boiler rooms across the country are starting to feel a lot emptier.

Modern propane and gas boilers used for commercial space heating and water heating have been revolutionized over the past 15 to 20 years, shrinking in size and improving in efficiency. The changes are creating the opportunity for businesses to achieve significant energy bills savings in both retrofit and new-construction applications.

“Gone are the days of filling up a huge boiler room with something the size of an Army tank, that lights off at full fire and is just burning gas,” says Trey Willbanks, president of Willbanks & Associates, a commercial heating systems equipment and support provider in Texas. “Everybody’s looking to go to the condensing, high-efficiency equipment. We’re using much smaller, refrigerator-size cabinets, lining them up, and modulating them down. That is absolutely the biggest trend in our industry.”

The energy savings come not just from the improved efficiency of the equipment, but also from modern boilers’ modulating capabilities. Older boilers essentially operate at one speed, Willbanks says, either full-fire or off. “Now one of my products has 33:1 turndown,” he says, referring to the ratio between full boiler output and low fire. “I just did a project where I lined up three 1-million-Btu units and cascaded them. Essentially it’s one system with 99:1 turndown. Back in the day, we would have been firing up the full 3 million Btus on every call for heat.”

“Any project with older equipment, we can without a doubt pick up 20-plus percent [in cost savings].”

The energy costs savings in those retrofit applications is “phenomenal,” Willbanks says. “Any project with older equipment, we can without a doubt pick up 20-plus percent [in cost savings]. There are some applications that are more extreme and we can pick up 50-plus. What we’re seeing a lot of is the ability to go in and retrofit equipment and get ROIs that pay for themselves in 1 or 2 years, with the gas savings alone.”

The space savings that can be achieved with high-efficiency propane or gas boilers is also an important advantage in new construction applications. Willbanks says his multifamily customers are changing their traditional designs from individual electric water heaters in each unit to a central propane or natural gas boiler system. The central hot water heating systems provide reliability, redundancy, capital and operational savings, and open up space in the units, all appealing options for developers. “If you can pick them up a closet and a few square feet, then that gets their eyes open,” he says. “Square feet is dollars for them.”

Maine’s Sanford High School will save more than $30,000 a year after switching from oil to high-efficiency propane boilers.

Heating intelligence

While traditional commercial boiler manufacturers are evolving to offer condensing, high-efficiency equipment, tankless water heater manufacturers such as Rinnai are making their commercial offerings more rugged and resilient with tankless rack systems designed for better reliability and ease of installation.

In addition, a newer manufacturer is also capitalizing on the modular, high-tech approach. Intellihot Green Technologies was founded in 2009 after a traditional water heater broke down and flooded founder Sridhar Deivasigamani’s basement, inspiring him to develop a more “intelligent” technology.

The manufacturer’s propane and natural gas commercial on-demand water heaters are designed for cascading operation, so they can scale up or down to meet variable demand. Larger units feature built-in redundancy, using multiple independent heat engines that operate as an integrated system. If any one of the modules experiences a malfunction, the remaining modules will continue to operate. The approach allows building owners to avoid the expense of installing redundant boilers and storage tanks while matching fuel consumption to actual demand.

Intellihot has also expanded the scope of its equipment to handle distribution of hot water. “Our device is able to figure out how a building is using hot water, and that may be different from school A to school B or hotel A to hotel B,” Deivasigamani says. “Our unit ends up adapting itself to that particular installation. It controls the building recirculation system so that we are not constantly circulating hot water, turning miles and miles of piping into large radiators. We achieve a nice balance between having immediate hot water and also saving on energy.”

Another benefit of Intellihot’s technology for buildings without access to natural gas is that it can be converted to propane without any hardware change. The installer just tells the software that the unit will be running on propane and turns a screw half a turn.

That type of dual-fuel technology is ideal for backup scenarios, Willbanks says. “If you’ve got any gas interruption or something like that, you can have a propane tank there as a backup; flip over and you’re ready to go.” For architects and building owners committed to designing resilient buildings, it’s an approach that could work in tandem with propane backup power to keep a building’s critical systems running even during a grid interruption.