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The prestigious The Caroline apartment building in New York City saves 15% to 20% per month in energy savings thanks to the installation of 17 condensing gas tankless water heaters. Photo courtesy of Bosch


When your tenants live in one of the premier rental buildings in the Big Apple, it’s crucial to have all operations working at optimal capabilities.

In 2012, the property managers at The Caroline, located in New York City’s Chelsea neighborhood, upgraded the building’s direct hot water delivery system. Out went three direct-fired water heaters and in went 17 Bosch C 1210 condensing tankless water heaters.

The swank Caroline property features maid and linen service, room service from the dining establishments in the building, a pet concierge, plus laundry and dry-cleaning service.

The original water heater setup featured two zones for the 430 apartments in the building. Zone 1 was significantly larger, delivering hot water to 317 apartments. The remaining apartments were set up in Zone 2, which delivered hot water to the top floors, including the penthouse apartments.

“It was orchestrated brilliantly,” says Jordan Stern, president of manufacturers rep Marplat.

Stern designed the plans and Bronx, N.Y.-based Paramount Plumbing Project Manager Mike Salera helped sell the project to the building owners and manager. During the retrofit, the engineers took the smaller zone offline and put the affected apartments into Zone 1.

“That was a major concern,” says Bosch Applications Engineer Tom Kelly, who was heavily involved in the project. “How do you transition without interrupting hot water?”

The project team, led by Stern, Salera and Kelly, got to work on removing the existing storage tanks and old water heaters. Space was limited in the rooftop mechanical room, but the new tankless models were easy to bring up the stairs and through the 30-ft.-wide doors.

“About three-fourths of the installation could be done prior to the removal of the old water heaters,” Kelly notes.

The job required 11 tankless water heaters to be installed for Zone 1 and six for Zone 2. The tanks for each zone are linked together with limited electronic equipment and their on/off function is based on flow. Zone 1 (lower zone) features four 280-gal. storage tanks and Zone 2 (upper zone) has three 280-gal. tanks.

“The tankless water heaters all fire together or they’re all off,” Kelly says.

“They’re behaving as one larger system and they’re piped to get flowing water equally through the multiple storage tanks.”

The team made sure the system runs at optimal levels during key times of the day,  such as the early morning and after-work hours when hot water demand is at its highest, Kelly explains.

He adds that the tankless units make use of cold ground water and have a 96% efficiency rating. Stern says the new system is saving the building 15% to 20% per month in its energy consumption despite noninsulated pipes.

“On Day 1, the old system was 80% efficient and dropped from there,” Kelly says.

The job took about one month to complete. Another key mitigating factor was the desire to keep tenants in the high-priced building — an Internet search shows rents per month at one time ranging from $2,500 (for a studio) to more than $4,000 for a two-bedroom unit — happy while the work was ongoing.

 “These busy professionals pay a high price to live at The Caroline,” Kelly says. “They expect to get what they paid for.”