Modern boiler control systems take advantage of cutting-edge automation to minimize downtime, simplify maintenance, and provide regulatory compliance. Parker Boiler, a Los Angeles-based manufacturer of hot water and steam boilers, was looking for such a system when it partnered with system integrator Diverse Devices to develop a PLC-based control system using an advanced PID algorithm.
Rather than using one large boiler to service the client’s needs for building applications ranging from hospitals to hotels, Parker Boiler and Diverse Devices partnered to create a system where multiple smaller boilers could be run in sequence while also delivering remote access for alerts, adjustments, maintenance, and troubleshooting.
The project requirements included a built-in, real-time clock and calendar; Modbus RTU and Modbus TCP IP communication protocols; embedded Ethernet; and data logging capabilities. Other key features needed in this application were data and alarm logging onto a removable SD card, the ability to download logged data via a USB flash drive, and a small footprint for the PLC and HMI.
The HMI interface provides intuitive control and monitoring of the boiler system. (Courtesy: Parker Boiler)
The PLC modulates the firing rate of the boilers, along with control of other functions. If one boiler is not sufficient to meet the heat demand, additional boilers are brought online by the PLC in a coordinated process.
This is accomplished either through Modbus RTU communication or by a 4-20 mA analog output signal, depending upon the Parker boiler type. Water temperature or steam pressure is measured by the PLC, and then using the PID algorithm, the firing rate is adjusted up or down as required to keep the temperature (pressure) constant.
Water temperature is typically the process variable of interest in hydronic heating applications, and steam pressure typically the process variable of interest in industrial processes. Hydronic heating systems use tubing to run a hot liquid beneath floor, along baseboard heaters, or through radiators to heat commercial buildings and other facilities.
Diverse Devices chose an IDEC MicroSmart FC6A PLC and a 10-in. HG3G HMI to develop the Parker Boiler solution.
"Setting up the PID function in the PLC using IDEC’s PID with Derivative Decay (PIDD) instruction is very easy, and the PIDD controller has a very fast reaction time,” said Noel Shamoon, chief programmer at Diverse Devices. “Tuning is quick and intuitive, and multiple changes can simultaneously be made to the PIDD parameters. This new PIDD function has helped eliminate undershoot and overshoot of set points in this and other systems.”
The entire control system including the PLC, the HMI, and other ancillary components is housed in a small enclosure, saving money and space. (Courtesy: Parker Boiler)
Remote Access and Operator Interface
The control system is connected to the internet through the HMI interface, providing browser-based access to the boiler system from any internet-connected device. This access allows alarms and alerts to be sent to local or remote personnel via text or e-mail.
Another provision is the ability to remotely monitor, diagnose, and upgrade the PLC program—accomplished primarily over a cellular network. Cellular was chosen over a wired internet connection to improve security, as well as to eliminate reliance on the end-user’s IT network. Program maintenance, troubleshooting assistance, and feature upgrades are all handled remotely by connecting a cellular modem installed inside the enclosure.
Alarms generated by the built-in functions of the PLC and HMI are pushed out as e-mails over the cellular network. “We have systems deployed all over the United States, and in a few foreign countries, and we never have to leave the office to support the controller,” said Shamoon. “IDEC has made it easy for us to connect remotely, and the ability to connect to a faraway system saves us and our customers substantial amounts of money, while also providing much quicker response.”
The HMI was programmed with accessible graphics and menus to make the Parker system easy to setup and monitor, with virtually no operator training required. The screens are self-explanatory, and Parker employs password-protected screens so an operator does not inadvertently change a critical setting. The alarm log, data log, and trend display features of the HMI are all utilized to provide information needed for troubleshooting and preventive maintenance. The entire automation system for control of up to eight boilers is housed in a 16-in. square enclosure that is just 8 in. deep.
IDEC also offered training classes to allow Parker Boiler employees to become familiar with PLC and HMI programming. “The nearby classes have provided tremendous value for us,” said Greg Danenhauer, VP of engineering for Parker Boiler. “We are now supporting our control systems and doing our own programming in-house…The ability to connect remotely has saved us thousands of dollars by minimizing the need to fly technical personnel to job locations.”
Jack Heiser is the president of Diverse Devices, a system integrator located in Orange County, Calif. specializing in the design of solutions for connecting machines and processes to the internet.