Company finds fix for ailing pool heating system

by arslan_ahmed | November 25, 2022 6:30 am

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By Tom Soukup

Close to Philadelphia International Airport, Presidential City, an apartment complex offering luxury living in Philadelphia, Pennsylvania, offers everything young, ambitious professionals could want, just outside the buzz of the city. Apartments range from studio to three-bedroom, with expansive fitness facilities, three pools, two hot tubs, five reflecting pools, and a myriad of outdoor entertaining spaces featuring full kitchens.

Post Brothers, a multi-family property development company based in Philadelphia, owns the property, operates several more in the area, and has made a point to set their properties apart with impressive outdoor facilities. As a result, large bodies of water at Presidential City, totalling 682,000 L (180,165 gal), remain heated year-round.

“The operational requirements of our outdoor pool club changed over the years,” says Sarina Rose, senior vice-president of development for Post Brothers. “We realized, although our residents and leasing staff appreciated the pools being filled all year, they were not being utilized during the winter. The residents do, however, use the Jacuzzis. To save energy and maintain the pools at just above freezing temperatures over the winter, we explored investing in a new pool heating system.”

High efficiency hydronics

Management at Presidential City called Patriot Pool Heating Co., in 2020, explaining the changes they wanted to make, and how the existing pool heaters were underperforming and consuming more natural gas than expected. Inspectors from the heating company found out all the units, which had already been replaced at least once in seven years, were no longer up to the task.

While there is no single key to successfully creating a pool heating system which will function for decades—successful planning must start with design. Choosing equipment built for longevity, eliminating contact between corrosive pool water, and the heating element is of utmost importance.

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Patriot Pool Heating has extensive experience conducting new and retrofit pool heating projects for retirement facilities, condominium and apartment complexes, resorts, hotels, and water parks. The method they employ, utilizing stainless steel condensing boilers as opposed to dedicated pool heating units, has been proven repeatedly to reduce maintenance, lower fuel costs, and provide improved comfort and system longevity. It is a departure from the norm in the aquatics industry, but it works exceptionally well, as their clients will attest.

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The heat is on

Initially, Presidential City maintained all its bodies of water at the same temperature during the winter. The resort’s new goal was to maintain the hot tubs at 38.9 C (102 F) degrees year-round; and the pools at 28.9 C (84 F) in the summer and 4.4 C (40 F) degrees in the winter.

The six existing pool heaters, which ranged from 400 MBH to 1.2 MMBH, had been failing at a rate of one every 18 months. Luckily, there was some redundancy built into the system for the pools and spas to remain at temperature, but the maintenance costs were extraordinary.

Initially, management only wanted to fix the existing pool heaters, but this was not possible.  Repairing or retrofitting the existing heaters was cost prohibitive due to the piping design being inadequate and not being installed as per the pool heater manufacturer’s specifications. Additionally, only one of the six pool heaters was of a high-efficiency condensing model, which can withstand low influent water temperatures. Yet, in the winter, influent water temperatures were as low as 4.4 C (40 F). The heat exchangers of the conventional, non-condensing heaters were constantly condensing; and condensate from gas-fired appliances is caustic, and will destroy conventional heat exchangers over time. The pool’s salt content was also degrading the copper heat exchangers at an alarming rate. To buy some time, these issues were temporarily fixed before a new heating system could be designed and installed.

Post Brothers’ main request was for the pools to remain at temperature, without fail. It was imperative to not have any inconvenience for their tenants. Once given the nod to proceed with a replacement, the design process began.

Robust design

Before starting the design, Post Brothers insisted the most important results of the replacement should be reliability, redundancy, and efficiency.

To begin the design phase, two separate calculations were needed, one for the hot tubs and one for the pools. Considerations included the volume and surface area of the water, ambient air temperature, and wind factor. Combined with the desired setpoint of the hot tubs and the pools, these figures provide a maximum heat loss. In this case, the plan was to use multiple modulating, condensing boilers. Condensing boilers are not only designed for low influent water temperatures, but they provide variable firing rates, allowing the system to efficiently accommodate the vast difference between the heat load in summer and winter.

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After deducting the efficiency loss across the 10 titanium shell-and-tube heat exchangers, it was determined that four, 800 MBH condensing boilers would be sufficient to provide the necessary heat. Combined, the boilers have an input of 3.2 MMBH, but because each boiler has 10 stages of input, the system can fire as low as 80,000 BTUH in situations where the call for heat is minimal. Unlike the existing pool heaters, which operated independently of one another and were dedicated to specific bodies of water, the four boilers operate together to produce heat for the entire system. The bank of heat exchangers distribute heat from the boiler loop to the pools for much greater redundancy.

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The new design is inherently more efficient and more dependable than the original. Most of the existing pool heaters were standard-efficiency, non-condensing models and had copper heat exchangers which were in direct contact with pool water. Those are negative attributes, a trade-off for a lower upfront cost.

“Patriot provided a design along with a cost analysis including energy savings and lower maintenance costs,” says Rose. “We realized the payback for the new system would be less than four years. It became obvious it was the right time for us to make this investment.”

No down time

The entire pool heating system was replaced over two weeks in the spring of 2021. The installation was complicated as the pools and spas remained at setpoint temperature throughout the project. However, since the pump room was quite large, it allowed the old units to remain in service while the new system was assembled. The project was sped up even further by prefabricating much of the boiler system offsite.

The four boilers are piped into a single large primary loop, delivering 60 C (140 F) water to the secondary loop, leading to 10 360,000 BTUH titanium heat exchangers. The larger bodies of water require more heat than a single exchanger can provide; therefore, several of the heat exchangers are on a manifold to serve these loads.

The beauty of the common boiler system is how it responds to any call for heat very accurately, whether a single hot tub is calling for heat or all bodies of water are calling at once. As soon as the lead boiler reaches 50 per cent firing rate, the second boiler will fire at low input and increase its capacity as needed, and so on. The system’s staging controls rotate the “lead” boiler on a regular basis, this ensures runtime hours are balanced across all the units. Unlike the original system, this simplifies service and extends boiler service life.

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In this system, the titanium heat exchanger takes the abuse from condensate, salt, or chlorine—not the heating appliance. Being titanium, they withstand the harsh environment very well. The system provides pinpoint accuracy in addition to longevity. Temperature in the pools and spas are maintained within one degree of setpoint, regardless of outdoor conditions.

“The maintenance and facility team are happy with the new system,” says Rose. “There was a considerable amount of apprehension about doing the work and taking some portion of the facility out of service, but Patriot made sure the pools were always open and at temperature throughout the project.”

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For years to come

Reliability, accuracy, and longevity were important considerations. Another consideration was fuel costs. The previous year’s gas bill for the pool area was $140,000, and now, the projected cost to operate the new system for a full year is $80,000, representing a 43 per cent savings.

Patriot Pool Heating is already in the process of designing a second, much larger system for the same real estate group. Presidential City features 464.5 m² (5000 sf) of water surface. This new project will be twice the size.

Author

Tom Soukup is the principal of Patriot Pool Heating Co., with more than twenty years as a hydronic designer and installer. He specializes in high-efficiency, green technology, and brings his expertise to custom commercial work, pool heating, and agricultural projects. Reach him at:
twsoukup@PatriotPoolHeating.com.

Source URL: https://www.poolspamarketing.com/trade/company-finds-fix-for-ailing-pool-heating-system/

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