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Pool Heater Resurrection

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Crystal clear, perfectly heated water has an appeal all its own. Lounging by a tepid, community pool offers bathers a great way to relax and unwind after a long day.

However, it is very unpleasant to anticipate this relaxation only to dip a toe in and find that the water is frigid. This unpleasantness can easily spiral into frustration when maintenance is unable to provide a timeline as to when the issue may be resolved.

 

The scenario

Tom Soukup is a specialist in hydronic heating across a wide variety of applications and owns and operates the Pennsylvania-based Patriot Water Heater Co. Soukup received a call from a local homeowners’ association (HOA) regarding a 719,228-L (190,000-gal) outdoor pool.

The heater had been installed four years earlier when the pool underwent significant expansion and renovation, but the facilities manager informed him it had not worked correctly since the install. Symptoms included the unit going into lock-out, substandard heat, and the continual need to be reset. Several repair companies had examined the unit but were unable to find a suitable fix.

 

Observations

Soukup and his team were called in to do a site survey. One aspect of the survey was to perform some forensic research on the chain of events leading up to the repair calls.

Soukup spoke to the facility manager to clear up some of the specifics in regard to the repair efforts:

  • How many companies had made service calls?
  • What did they do?
  • When was the service performed?

 

Establishing a chronological order was important, as this would help develop a timeline of the noted issues and provide some insight as to why previous contractors were not asked back for further repairs. For example, Soukup discovered that when the first technician examined the unit, the heat exchanger was clogged with soot because of improper water flow. The unit fired and the technician burned himself. In this instance, proper safety protocol was not followed.

The pump room was located beneath the water line of the pool. As the installation was a retrofit, there was not enough room to install an outdoor heater. The initial contractor opted for an outdoor heater installed above the pump room, as this was the only logical location.

The contractor relied on the heater’s internally installed circulation pump to move water from the filter to the heater. They also opted to go with 1.825-million British thermal unit (Btu) pool heater.

When starting the pumps, Soukup found a tremendous amount of air being circulated through the system, which was causing the pumps to cavitate. This observation prompted him to request a walkthrough with a facility manager.

The original contractor installed a float style air eliminator at the heater. With Soukup’s experience in hydronic heating, he understood float type eliminators let air out, but also let it back in.

Because the unit was above the pump, whenever the main pump went off, it sucked air back in the system. This caused lack of flow and a low water condition. The issue was brought up to a previous contractor, who bypassed the low water cutoff safety device. In turn, the unit could dry fire—which is certainly not advised.

 

Process

As part of the ‘autopsy’ procedure, Soukup disabled the ignition system, making sure the unit was unable to fire but still able to run the pump. The facility manager verified these symptoms matched what they had been experiencing.

After pressurizing the system, Soukup ensured there were no leaks and the heat exchanger was sound, and then began to prepare the technical data. He knew the active failure points, but needed to identify the passive failure points (i.e. a gas pressure, water flow, or current draw). Soukup took the measurements of the pipe length and fittings, calculated friction loss, and then needed flow rates.

At this stage, it was time for research: reading the manuals, consulting technical papers, and reaching out to factory support reps. Soukup discovered the manufacturer specifications required 681 litres per minute (lpm) (180 gallons per minute [gpm]) of water flow across the face of the heater with closely spaced tees for hydraulic separation. In instances when the heater is installed above the pool’s water line, specifications dictated the primary piping be a minimum of 457 mm (18 in.) above the heat exchanger. This prevents the heat exchanged from draining back when the pumps are deactivated.

Because the primary filter pump was being partially bypassed through the heater, it would not be able to achieve the flow rate required. This resulted in flow reduction through the main filter loop.

By calculating the friction loss of the piping at the required flow rate, Soukup was able to size a correct booster pump.

 

Resurrection

By this point in the assessment, Soukup and his team had gathered enough information to determine the cause of the equipment failure and establish how to resurrect the system.

They developed a plan with multiple stages:

  1. Rip out the existing primary piping and reinstall the correct size to accept the required flow.
  2. Install the booster pump in a primary/secondary fashion with hydraulic separation off the main filter loop.

 

Hydraulic separation was used to de-couple two loops with different flow rates, which achieved two positives: getting a higher flow through the filter and getting the correct flow across the face of the heater for optimal performance.

Standard procedure requires a replacement of the low water cutoff with a new flow switch on the heater. Upon removing the old flow switch, Soukup found the original installer had stacked four paddles on the actuator—despite the installation’s instructions stating one paddle of the correct size should be installed.

That said, after planning and calculations were complete, Soukup and his team began their job of undoing the mistakes of the previous contractor. All piping and external controls were removed, leaving them with just a heater on the equipment pad and the primary filter loop.

The contractors cut into the main 152-mm (6-in.) filter loop with two closely spaced 76- x 152-mm (3- x 6-in.) tees that would feed the booster pump and provide pump de-coupling.

Soukup ran 76-mm schedule 80 polyvinyl chloride (PVC) piping into the booster pump with true union valves for pump service ability. He continued to run these lines with assorted tap tees in place for flow switches and other safety devices.

Then, Soukup core-drilled new holes through the equipment pad under the heater and above the pump room and continued the 76-mm piping through the pad at a minimum of 457 mm (18 in.) above the pool heater’s heat exchanger. The team then installed a second set of 76 x 63.5 mm (3 x 2.5 in.) closely spaced tees to de-couple the internal heater pump from the booster bump. This allowed a 681-lpm (180-gpm) flow across the face of the heater through the pipe.

As per manufacturer specifications, from the tees down to the heater, Soukup and his team installed an H-crossover which gives the ability to adjust the flow rate of the internal pool heater pump, with valves if temperature blending was necessary. Temperature blending allows for hot and cold water to mix and supplies tempered water into the input side of the boiler to prevent thermal shock and condensing of flue gasses inside the unit. They installed as many unions and valves as possible for ease of future service and usability.

 

Success

At this point, all piping had been completed and the heater was in. Thermometers were installed on the supply and return of the heater to display the Delta T, or temperature difference, of the heater.

For safety devices, Soukup added a manual reset, high temperature limit, as required per code in the site’s locale. A flow switch was installed in the booster pump loop, which meant the heater would not be able to fire unless the booster pump was running. This precaution would prevent dry fire and avert the disaster the client had previously experienced. Upon installing these devices and performing the correct electrical and safety device wiring, they were able to push water through the system and check the flowrate.

According to the flow meter, the flow on the main filter loop increased by approximately 15 per cent, which was within the provided specifications. The meter on the booster pump loop said the mathematics worked out correctly and was getting 681 lpm (180 gpm) across the face of the heater.

Next, the installation team turned on the internal pump to remove all the air from the system. This meant no more cavitation.

The team then turned on the heater with ignition systems disabled to ensure all safety devices were working properly. The unit attempted to fire but, with the ignition system disabled, it could not. They turned off the booster pump and the heater went into lock-out, as expected. This was the proper chain of events.

Soukup and his team felt confident to re-enable the ignition system. Right as rain, the heater turned on. The company’s standard procedure dictates its employees perform a proper start-up as if the system had never been installed before. This procedure meant checking gas pressure, all safety devices, and the overall safety and functionality of the unit.

 

Conclusion

This case study is an example of the successful reinstallation of a malfunctioning heater. It is challenging to understand and gather all the information available from manufacturers, sales representatives, and technical support, and then successfully execute such a task. More than anything, it is invaluable to understand the craft; installing a piece of equipment is not as simple as dropping stuff into place, attaching pipes, and walking away.

The customer was pleased by the work and asked Soukup and his team to look at another heater in the community that had been installed by the same contractor which was beginning to exhibit the same problems.

When hiring contractors for various pool needs, clients should not always choose the lowest bidder. The saying is true: “the bitterness of low quality outlasts the sweetness of a good price.” When a contractor truly understands and cares about the result, a customer will end up with a better install and better support to follow.

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