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Case Study: Launching a Nationwide Equipment Network

A look at how Alta Refrigeration achieves faster, easier product development and servicing with groov EPIC and MQTT.

Benson Hougland Opto22

What’s the secret to providing superior service and staying competitive in a changing market? Well, you might learn something from Alta Refrigeration’s experience. Over 10 years, it transformed itself from a custom engineering services company into a scalable industrial equipment manufacturer using an edge-oriented control architecture to efficiently manage a growing installed base.

Alta has been designing and installing refrigeration systems across the United States for more than 45 years. For many years, these systems were large, custom-designed systems that used a central machine room to deliver refrigerant to various facility areas through long, overhead piping runs. Due to their size, these systems required significant time to design and program, and competitors were able to steal some of their market share with cheaper, simpler offerings.

“Competitors could use 20-30 cheaper units with control limited to a dumb thermostat to compete against one of Alta’s large systems,” says Peter Santoro, controls engineer at Alta.

Alta knew it couldn’t compete by reducing its product quality, so the company looked for a way to standardize its offering without sacrificing features.

We’re the Experts
In 2013, Alta introduced its Expert series of modular refrigeration control units. Each unit uses a standard, reliable design and can be mounted on the roof above the area it served, simplifying installation.

“A single Expert has almost as much I/O as an entire centralized system and, because the units are much smaller, the wiring and conduit runs are incredibly short, allowing us to cram in a ton of sensors,” explains Santoro. “The units themselves are also incredibly efficient. We analyze external ambient conditions and refrigerated space and do real-time thermodynamic calculations. This lets us do variable capacity refrigeration, and only run exactly the amount of refrigeration as needed. All motors are on variable speed drives. We also design many of the sensors we use on the system, allowing us to get precise valve positioning and monitor refrigerant levels throughout the system. We make good use of Hall effect sensors in various configurations to monitor refrigerant levels and motor positions. There is also a dedicated energy monitor on each unit so we can monitor voltages and power usage.”

Since all Expert systems are essentially the same, Santoro and his colleague, Todd Hedenstrom, were able to focus on creating a robust and complete solution that works for many different applications.

A good problem to have
Market response to Expert has been very positive. Alta has sold nearly 600 units and is typically sold out into the next year. But growth brings its own challenges. With only a small controls engineering team, servicing the growing installed base became time-consuming.

Adding to this time crunch, some aspects of Alta’s previous designs related to system maintenance issues. For example, the control system required numerous steps to properly update control strategies in the field, including exchanging files between the control engine and the web server used for remote connectivity. And because Alta had previously left the details of remote connectivity to each customer, this increased the team’s workload by requiring them to check in on each site every day using different methods—such as VPN, Citrix, LogMeIn, and TeamViewer.

Alta’s centralized control system design was built around an industrial PC (IPC) running custom C++ code on top of a distributed I/O system from Opto 22. When designing Expert, this control system was simplified by replacing the IPC with an Opto 22 PAC (programmable automation controller).

Though this change was an improvement because it allowed for all the components of the system to be managed through the PAC, it still required a multi-step update process and didn’t provide as much data access as Alta wanted. This led Alta to explore use of Opto 22’s groov EPIC (edge programmable industrial controller) system.

EPIC supports all the power, I/O, communications, storage, and networking functions of an IPC and PLC on a single backplane without the complexity of maintaining a full Windows OS environment.

Web interface via the controller
Santoro and Hedenstrom started by using groov EPIC’s operating system shell to port their PAC application to C++.

The new program controls the installed I/O modules—voltage and current sensing inputs and discrete AC outputs—using Opto 22’s C++ OptoMMP SDK (software development kit). The application also includes its own Modbus server that creates and manages connections to variable frequency drives, the local energy monitoring unit, and other remote devices.

“We [also] have our own REST API and webserver running on the C++ application,” Santoro adds, “allowing us to create our own web page interfaces in HTML and Javascript,” such as a Google Chart API (application programming interface) to display energy metrics in the HMI.

Each Expert web interface is served from an EPIC controller. The interface includes prebuilt templates for different unit configurations and verifies system settings to help technicians identify configuration values that are out of range or not recommended. It also generates alarms as needed. Alternatively, customers can access unit data through the Expert’s Modbus server or REST API.

For managing groups of Experts, Alta uses a separate HMI server to read data from each unit and present a unified view of the entire system. “All of our sites are required to have a local interface for operators to see a global view of their refrigeration units, instead of having to manage network connections to hundreds of individual units,” Santoro explains.

To create this site-level HMI, each Expert stores transient data in the shared memory scratchpad area of the groov EPIC. Alta’s HMI server runs on Windows and uses Opto 22’s .Net OptoMMP SDK to retrieve data from all units in one-second increments. Data is stored in cyclical files that maintain a oneweek buffer, and the HMI server uses this data to generate trends, charts, and email notifications.

Alta can also access this data remotely for troubleshooting recent events. By default, groov EPIC does not route traffic between its Ethernet ports, so Alta can use the controller to create a security zone for each Expert. One port on each EPIC connects to a private network exclusively for the controller and its remote devices. The other port is connected to a common network between all the units at a given site, as well as the local HMI server.

This server is connected to the internet and uses MQTT to send and receive data, acting as a middleman for each individual Expert to the MQTT broker that resides in Alta’s headquarters. When Alta’s remote HMI requires new data, it sends a request to the local server over MQTT. The data is then queried and sent back. External connections to local HMI servers are restricted so that the only traffic allowed through is from outbound MQTT TLS connections.

Recently, Alta also made it possible for customers to access this remote server. The server has its own database that records temperatures and energy usage for each Expert in 10-minute intervals.

Nationwide data aggregation
Using groov EPIC, Alta has now built a nationwide HMI that aggregates data from its network of Expert units and highlights any issues the team needs to act on. Instead of spending hours every day to check on each site, they can monitor their entire installed base in minutes. They know when there is a problem, can input and track necessary work orders, track technicians’ locations, and monitor energy usage per unit. When an alarm occurs, the system creates an interactive timeline of events before and after the alarm event.

“Often, we know what the problem is before the customer calls. We just need to drive there and fix it,” says Santoro. “With the amount of data we get from our units, we are capable of diagnosing the vast majority of problems remotely. This allows many of our end users to not even staff on-site maintenance. And there’s no interfacing with third-party systems anymore. It’s all integral.”

Servicing the systems themselves has also become much simpler now that Alta can manage the entire platform—I/O configuration, control strategy, communications, and networking—through a single device. “One of the best features we introduced was the ability to update the programs through our web interface. Now a batch program packages all the program files into a .gz (compressed) file. Technicians can upload the file and restart the system,” Santoro says.

Alta also uses the groov EPIC’s touchscreen as a maintenance interface inside the control cabinet. The native groov Manage application allows them to view and modify I/O and network settings directly on the controller without using a separate computer interface. Using the EPIC’s native HMI server, groov View, Alta also provides technicians with local control options and basic information about the Linux program’s status.

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