Early in 2016, one of KMB Plumbing and Electrical, Inc.’s commercial customers referred them to Golden Living, a skilled nursing facility in East Stroudsburg, Pennsylvania. The building’s existing storage-type, electric water heating system had begun to fail. Temperature fluctuation was a problem, as well as the inability to meet peak demand.
“The old tank was a build-on-site system from the 1970s,” said Kevin Berry, KMB’s owner. “It’s a wonder it worked at all. Its only saving grace was its several-thousand gallon capacity.”
After speaking with Mike Hetzel, who at the time was executive director at Golden Living, Berry learned quickly why the domestic hot water system was so big. The 137-bed facility, complete with commercial kitchen and laundry, requires upward of 40-45 gallons per minute of hot water.
To make things more complicated, two different supply temperatures were needed. The big tank was maintained at 170 F and mixed down to 112 F with a large tempering valve before entering the building’s three-quarterinch domestic hot water recirculation line. The reason for maintaining a high tank temp was two-fold.
The various appliances in the kitchen, as well as the laundry, call for a temperature of 160 F. Even more importantly, Legionella bacteria can’t survive at higher water temperatures. This is critical in an elder care facility where residents are more susceptible to Legionnaires’ disease, the illness caused by the bacteria.
Berry began calling manufacturers of both gas-fired volume water heaters and smaller tankless water heater.
After learning that the existing water heater would need to remain in service until the new system was operational, the search narrowed to wall-hung condensing models, based on space constraints. After speaking with several manufacturers, as well as local wholesaler, APR Supply, about the project, Berry decided to design the new system around the stainless steel Navien NPE- 240A tankless water heater. APR’s Cory Drozal was a valuable resource both during design and installation.
Over the course of a long week, a fourman KMB crew hung 11 of the 199,900 Btu/hr tankless water heaters in the basement mechanical room. The 6-inch PVC venting was installed even before gas lines or copper piping were added. Between a door and the electrical service, there was just enough room on the exterior wall for four penetrations.
Up to eight Navien NPE-240A tankless water heaters can be common-vented, but the need to supply two water temperatures meant separate and independent water heating systems. Five units serve the kitchen and laundry room, set to 160 F, and six units provide 111 F water to the resident care areas.
“The kitchen was one area where the old system came up short,” said Dan Piccolo, director of maintenance at Golden Living. “The washing machines wouldn’t get dishes clean enough on the first pass, so the kitchen staff was excited about the retrofit.”
From venting to piping, the project moved quickly. Included within each NPE-240A cabinet is a domestic hot water circulator, allowing the units to provide DHW recirculation to the facility without any external pumps or controls.
The units feature efficiency levels of up to 97 percent, as well as a 10:1 turndown. This means that, in addition to plenty of redundancy, the multipleunit approach provides the 55 stages of input for the high-temp loop, and the low-temp loop has 66. The NPE-240A also features ComfortFlow technology, which pairs a 1/3 gallon buffer tank with the internal recirculation pump to provide instantaneous hot water to all fixtures within the building. For projects seeking LEED certification, the NPE-240A provides up to three points.
ONE LATE NIGHT
When the only thing left to do was fire the water heaters, KMB picked a night to transfer the DHW load from the existing unit to the Navien system. At 2:30 a.m., they cut the four main lines and connected them to the shiny new copper. Within an hour, the systems were circulating water at steady temperatures.
The old water heater still needed to be torched apart and hauled away. But that gave KMB Plumbing and Electrical an extra day to observe the new system in operation. It also gave them a day to listen to accolades from Golden Living staff members.
“The new system is quite awesome,” said Hetzel. “The water temperature no longer fluctuates and we haven’t heard a single resident complaint. It’s done everything that Kevin promised, and then some.
This article was originially published in the Spring 2018 issue of HVAC/P Magazine.