United States. Benjamin Franklin House, in downtown Philadelphia, needed an HVAC overhaul but, like most historic buildings, had no room to expand. Evapco searched its archives for the specifications of the building's original cooling tower and created a more powerful and updated version for the same space, facilitating the installation process for Elliott-Lewis Corporation.
Time for an update
The Benjamin Franklin Hotel, now known as The Franklin Residences or simply "The Ben," was built in 1923. Upgrading historic sites usually presents challenges, such as limited space. The building's owners recognized that keeping tenants and guests comfortable during increasingly hot and humid summers would make the right systems and equipment work with minimal or no downtime.
A key component of The Ben's cooling system is the cooling tower that serves a water heat pump circuit in the building. For many years, this circuit met most of the building's cooling needs. Several suites still use packaged terminal air conditioning units, but many tenants have requested the switch to heat pumps. In addition, the commercial space was expanded from one floor to two. These changes have increased the demand on the heat pump circuit.
Mike McCauley, a sales engineer at Elliott-Lewis Corporation, explained yet another reason for the increased demand. "Some equipment loses efficiency as it ages. When built, the system was designed to meet certain demands. Well, those demands have changed. We have warmer summers now, and that's burdensome for older teams. It can have the best maintenance in the world and [the system] still won't be as efficient as it was before."
The increased demand didn't come with more floor space for a second cooling tower or even a new, larger one. Owners faced a challenge: how to get more cooling capacity using the same footprint. At the same time, the existing cooling tower, which had served the building since 1984, was nearing the end of its useful life.
"Our company maintains the cooling tower at this site," McCauley said. "We realized the equipment was at the end of its useful life and told the owners that if they didn't replace it soon, they would be spending a lot of money to restore it."
The old meets the new
When the original cooling tower was built, it was not subject to certifications or ashrae 90.1 requirements, and the building codes were also different. The building needed a new cooling tower that met current requirements, but had the same footprint and greater capacity. Engineers were called in to tackle the design, and Elliott-Lewis Corporation, which has served Philadelphia for a century, was chosen to install the new cooling solution.
The original cooling tower was a discontinued Evapco unit, a PMTQ cooling tower. Therefore, the brand recovered the design of its files and built a new one to meet all the requirements of the project, including a strong demand for cooling, maintaining the same footprint. Evapco's solution increased the cooling capacity of the system in the heat pump circuit from approximately 565 tons to 675 tons, without sacrificing space.
The original galvanized material was replaced by stainless steel, ensuring durability and a long service life. The addition of a custom fiber acoustic base for the tower ensured that the new unit was fully compatible.
The new tower also needed to meet or exceed current codes for thermal and acoustic performance. The building is located in a densely populated part of Philadelphia, surrounded by office buildings and residences, so noise is a concern. The new unit features Evapco's super low sound fan instead of the typical centrifugal fan that would be used with a forced draft system.
In addition, the unit has four fans with a total of 60 horsepower, compared to the 40 horsepower of the original unit. Despite this increase, which achieves a higher capacity, the performance of the unit is more energy efficient at partial loads. Each fan is driven by a variable frequency drive (VFD) designed to operate at partial loads rather than turning on and off when demand changes.
With VFDs, the unit can run all four fans at, say, 30 percent, which is much more efficient than running a fan at 100 percent. The unit only uses the necessary energy on any given load.
Overcoming other challenges
The heat exchanger, originally designed to meet the lower demand, would not serve the upgraded cooling tower to provide additional cooling to the building. Instead of replacing the heat exchanger, the owners opted to modify the existing equipment. As there was enough space to add extra plates to increase capacity, the original heat exchanger was cleaned and expanded.
Replacing the old cooling tower with a modernized version allowed minimal piping, saving Elliot-Lewis time. "There were some changes to the pipelines," McCauley said. "The old pipe was replaced due to its age, but other than that, there was only a change of route of the pipes to accommodate the new dimensions of the tower."
Cooling tower control required the integration of the unit's VFD controllers into the building management system. This step proved to be challenging at first, but since its inception, the unit has been able to meet the required performance without complaints from owners. With its resilient team and supportive professionals, The Ben is sure to maintain its reputation for luxury for many years to come.
