Case Study: Fun in the Sun, Courtesy of Variable Frequency Drives and Resourceful Maintenance Staff

Summary

Summer is synonymous with soaking up sunshine and outdoor activities. At Triple R Camping Resort in Franklinville, New York, things are no different. With more than 200 sites for tents, campers and recreational vehicles (RVs), there is no shortage of people waiting to make use of the best summertime amenities.
 
Recently, Triple R introduced a splash pad to their resort offering. The LeeKee Lagoon, which consists of several interactive water features including water cannons, water curtains, a tipping bucket and a 4-lane racing slide, complements the existing pool and hot tub and provides a place to relax and unwind for those young and young at heart. See this area in the photo at the top of the article. The water attractions at Triple R Camping Resort are controlled by three separate water systems (pool, spas and splash pad) in the pump house.
 
Due to the large-scale nature of the project, a systems integrator (SI) was selected to design and implement the control system for the splash pad. Part of the responsibility of the SI was to evaluate the environment and determine requirements for operating the pumps, which would ultimately feature two variable frequency drives (VFDs).

 
Assessing water pumping requirements

An early design decision was to consolidate the water feature pumps to make operation simpler and more efficient. Instead of relying on multiple small pumps the system was revamped and optimized for two 7.5 horsepower pumps driven by three-phase motors.
 
Another key consideration was the water purification system. In this case, ultraviolet (UV) light is used to sanitize the water before it flows through the features. The UV filtration system kills any microorganisms, but the lamps generate heat in doing so. Therefore, keeping the water flowing is essential. If there is a problem with a pump or water flow, the UV equipment must immediately shut down and vice versa.
 
The system was designed for the pumps, and therefore the VFDs, to operate in parallel, using a single proportional-integral-derivative (PID) control loop. The goal of the PID is to maintain consistent water pressure throughout the system. One VFD is the lead, and it communicates to the second VFD using a serial protocol. This ensures both VFDs operate cooperatively. If each VFD used its own PID loop, they would fight each other, and control would be unstable.
 
Protecting the system parts and components from mechanical and thermal stress is essential. An important attribute of any system that includes water flowing through a network of pipes is the ability to maintain constant water pressure. Ensuring the system pressures ramp up and down protects the pipes from surges when valves open or close, commonly referred to as the dreaded “water-hammer” phenomenon. When VFDs are utilized and configured with ramp times, pump life is extended and the plumbing is better protected.
 
The equipment room at the resort contains three separate water systems—pool, spas and the new splash pad. With the UV purification light bulbs operating at temperatures of 600 °F (315 °C), and the added heat from other pumps, motors and controls, combined with ambient temperatures on a hot summer day, the equipment room can reach high temperatures. These conditions would play a factor in the automation design.
 
On the controls side, the three-phase pump motors presented a new challenge. The resort is in a rural area and did not have access to three-phase industrial power from the utility service. Because only single-phase utility power was available, the VFDs would need to be capable of working this way.
 

Selecting a VFD that checks all the boxes

When evaluating VFDs for this project, the designers knew there was a wide range of options varying in price and complexity. After considering multiple manufacturers, the DURApulse GS4 drives from AutomationDirect were selected (Figure 1).

Going with the flow

As valves open and close due to normal operation or fault conditions, water may be redirected from 8-inch main pipes into a bypass system with 6-inch pipes or open water holding tanks, resulting in widely varying backpressure conditions. A ProSense pressure transmitter from AutomationDirect was selected to monitor pressure in the UV filtration system and provide the value to the VFDs for PID control (Figure 2).

Treading water

Shortly after the SI turned over the project and put it into service, disaster struck. Days after commissioning the new splash pad, a pipe burst in the control room. The LeeKee Lagoon would be out of service due to a major water leak. In addition to the failed plumbing, the resulting water damage also impacted the electronics and controls for several of the splash pad features. Replacements would be needed, and fast.
 
However, as is often the case when failure strikes, the timing couldn’t be worse. Because the SI had moved onto their next project, they were not available on short notice to oversee the repairs. Getting the splash pad back up and running would be left to the resort staff.
 
With no time to waste, the search for replacement parts began. There was good news and bad. With the project being recently completed, the documentation was accurate and readily accessible. The SI provided a detailed report including schematics, model numbers for all products used, and even a hard copy of the programming settings when the project was commissioned. The not-so-good news was a key component of the system—the VFDs—were not in stock and the resort staff did not have any prior controls programming experience.
 
A call to AutomationDirect’s technical support line quickly sorted out the issues. The technical support representative provided guidance for selecting the drive. The dual rating for 3-phase and single-phase input power was straightforward to understand, even for a novice. Ultimately, a slightly oversized drive was selected for the replacements (25hp with 3-phase input, 10hp with 1-phase input) with added margin to help the drive run cooler in the warm control room.
 
With some phone support, the staff at the resort was able to diagnose the problem, identify and select replacement parts, place the order and coordinate shipping. The initial call was on a Monday morning, and the parts were installed by the following Wednesday morning. As an added benefit, both the original and replacement drives were a C-frame size, so the physical footprint for mounting was the same. The programming process was quickly and easily completed once the drives arrived on site.
 

Looking to the future

Learning from this incident, additional VFDs and a pressure transmitter were purchased to keep on hand at the resort as spares. The VFDs boast several features which help future-proof the resort’s investment should additional functionality be added to the control system.
 
As an option for programming the spares, the VFD is equipped with a smart keypad designed to quickly configure the drive. Up to four configurations can be stored and then transferred to other VFDs. The VFDs are available with high-speed communication interface options, such as Modbus TCP and EtherNet/IP. While the current system is monitored manually with hourly checks for flow, pressure and chemistry, future networking upgrades at the site will make it possible for remote monitoring and alarm annunciation of these conditions.
 
Another feature of the VFDs is a built-in programmable logic controller (PLC). Although the system is currently operating with closed-loop PID control, additional logic can be incorporated in the future to monitor and control other I/O points and create even more advanced logic functions.
 
The waterpark—consisting of a pool, spa and splash pad—is one of the most popular features at the resort. Nearly a quarter million dollars of equipment and plumbing is now effectively and safely controlled by two VFDs costing just a few thousand dollars. The Triple R maintenance staff takes comfort in the fact that behind-the-scenes the AutomationDirect DURApulse GS4 VFDs keep systems running smoothly, and they can easily manage the equipment and expand in the future.
 
_{All figures courtesy of Triple R Camping Resort}