Tankless rack water heating meets a courthouse's unique installation needs
For Wisconsin's Jackson County Courthouse, a preassembled water heating system kept energy costs, and disruption to water services, at a minimum.
By Selby Frame
The historic courthouse in Wisconsin's Jackson County serves a population of nearly 20,000 and includes an annex to the sheriff's department and county jail. So when its aging, 2-million-Btu boiler and 725-gallon tank-style water heater needed updating, county officials knew they needed a replacement system that would meet large, varied demand with minimum disruption to water services for inmates.
The need to guarantee that the new system would be up and running quickly was a matter of law: Access to hot showers and clean laundry is part of an inmate's rights to sanitary conditions.
Brian Eirschele, principal and mechanical engineer with Seattle-based Eirschele Consulting Services, was brought on to lead the project and quickly began researching tankless options. "I knew the courthouse team wanted to go to an instantaneous system," Eirschele says. "They're very forward thinking. I was interested in energy savings and a good [environmental] footprint. That was as much direction as we needed."
Fueled by propane or natural gas, condensing tankless units can provide energy savings up to 40 percent over conventional, electric water heating systems while providing an unlimited stream of hot water. Multiple tankless units can be banked to create redundancy, so the hot water supply will continue even if one unit is out of commission. They also come in a variety of pre-fabricated rack options that make them ready for easy load-in and installation.
The team reviewed several systems and selected the Rinnai Tankless Rack System (TRS), outfitted with six Rinnai 199,000-Btu condensing tankless water heaters with 95 percent efficiency. "We chose condensing heaters for flat-out efficiency," Eirschele says. "The units are absolutely great. I'm sure we'll look at end-of-year energy consumption and see great savings."
Condensing tankless units are a smart choice for buildings that use large volumes of water because they reduce energy losses from flue gases. These units capture the latent heat of exhaust before it escapes into the vent system and use it to pre-heat incoming ground water, which circulates through a secondary heat exchanger. Cooled exhaust then condenses into water vapor and drains from the appliance.
The courthouse should also see improved efficiency from the superior turn-down ratio of the Tankless Rack System, says Trey Hoffman, global product manager at Rinnai America Corporation. "That allows the Rinnai units to modulate gas input precisely to meet the hot water demand on an instantaneous basis."
The Rinnai TRS is available in free-standing or wall-mounted options for indoor or outdoor applications. Because space was limited, the Jackson County Courthouse units were configured as a freestanding fabrication that would fit fully assembled through the mechanical equipment room doors.
The bank of back-to-back RU98i tankless water heaters was shipped to the site pre-assembled, with all gas piping, water piping, combustion-air, and exhaust-air piping and controls already installed. Rinnai's TRS units feature a lead-lag system that rotates the firing sequence of the water heaters, ensuring the load is distributed evenly over all the water heaters. This greatly improves the system's efficiency and life span.
"The unit was simply moved into place and our connections were at a single point," Eirschele says. "That meant that the plumbing contractor just had to connect up to the unit. They didn't have to do any internal piping at the RU98i skid, which made installation much simpler."
Fully installed, the unit measures 62 inches long, 28.5 inches wide, and 56 inches tall.
Common venting, uncommon ease
The primary installation challenge for the courthouse was to design a venting system that could be adapted for limited roof access. "We had a tight space to cut through concrete," Eirschele notes.
Rinnai's TRS is available with a common venting system on top, which allows the entire rack to use the same exhaust and intake venting. That way, the number of interior venting runs was shortened. "Once we got to the roof, it was as simple as two bites: one for combustion, one for exhaust," Eirschele says. "It made installation much easier."
What really made the case for the courthouse retrofit was the ease and speed of installing a TRS, which took just a few short weeks from idea to implementation. "The [manufacturing] rep came to turn it on and ensure the units were sequencing and operating as they should," Eirschele says. "When he left the site, they had a running bank of units. From the time we had no hot water to the time we had instantaneous hot water was less than two hours."
If you're looking for an efficient and flexible water heating system for your next commercial construction project or energy retrofit, the Propane Products and Appliances Directory is a great place to start. The interactive tool allows users to search for residential or commercial applications, and it's freshly updated with commercial products in every category. To learn more about efficient water heating with propane, check out these Propane Energy Update articles: