rkc thermostat – five advantages of thermostat over PLC

Programmable logic controllers (PLCs) and temperature controllers (thermostats) offer similar benefits in ensuring effective process control, achieving consistent quality, and minimizing user error in manufacturing.

Since the 17th century, process control equipment has been present in a variety of forms, such as temperature regulators in furnaces and later flying ball governors in steam engines, boiler valves, and other mechanical systems in the 18th and 19th centuries.

PLC is a more modern tool that emerged in the 20th century, especially in the 70s, with the growing demand for factory automation. Prior to PLCs, their function was achieved by a series of mechanical components that were extremely expensive to install and repair, and were very complex and difficult to change when adjustments were needed at the factory, such as product line upgrades.

However, despite the many similarities between temperature controllers (thermostats) and PLCs, there are significant differences in their setup, programming, and application, and the combination of these differences makes temperature controllers unique:

1. Cost savings

Of course, this is relative, PLCs are designed to control multi-tasking, suitable for multi-temperature loop control applications. For some single-loop, or a small number of loop-controlled applications, many features of the PLC are not required by the application, so the cost is high, it is better to choose a controller specially designed for temperature control.

2. Easy to set up

As mentioned earlier, PLCs are designed for multi-tasking environments, so they require specialized programming skills and a lot of time to create a solution that meets the needs of a specific application. Temperature controllers, on the other hand, can be installed, set up and optimized relatively quickly (e.g. PID controllers) and require very little experience.

Many temperature controllers can be panel mounted, i.e. they can be mounted on the front panel of the process machinery, and have a visual screen that can be set up in minutes with only basic engineering knowledge. PLCs, on the other hand, are more complex, are typically mounted in a rack behind a panel, do not have a display, and require a separate HMI (which also needs to be set up), so ease of setup is at a disadvantage.

3. The temperature control function is better

Temperature controllers (thermostats) are specifically designed to handle specific industrial processes and therefore include features, outputs, and control functions that are directly related to these processes, such as specialized algorithms for applications that require valve-motor drive control (VMD). PLCs need to be suitable for a wide range of manufacturing and automation functions, so the features for temperature control are limited. They can perform basic temperature control tasks, but they are not as advantageous as specialized temperature controllers. In addition, temperature control systems place very high demands on the microprocessor due to the processing of analog signals. Temperature controllers (thermostats) are designed to handle these demands, and the PLC must be tested before the system can meet these process requirements. If it fails to meet the requirements, the PLC will not be able to respond quickly to various changes in the process, and lead to lead or lag, which will affect the quality of the product.

4. Clear visual interface

Panel-mounted temperature controllers come in a variety of sizes and levels of complexity, so operators can easily view process information as well as warnings or alarms that need attention. PLCs usually do not have a direct interface, but instead require a separate HMI, and the HMI needs to be set up individually. HIMI can display the necessary process information, but it also usually displays various data related to other tasks managed by the PLC. This means that the advantages of a panel-mounted temperature controller are obvious, as it has a dedicated interface for easy access to all relevant information and can be adjusted quickly. Many temperature controllers additionally provide data logging capabilities that can be used to view previously made changes and flag potential problems.

5. Accuracy

The temperature controller (thermostat) is part of a closed feedback loop that actively tracks the deviation of the process value from the set value and adjusts the power level as needed. Many controllers have PID algorithms with automatic adjustment for fast set-up and minimal deviation from the process value. This includes adjustments to unexpected process changes or interruptions, such as when the oven door is open. This is necessary to maintain consistently high product quality and to reduce the number of bad product batches.

PLCs also sometimes have PID capabilities, but unlike temperature controllers, their PID capabilities are often limited or require engineers to manually adjust, which makes programming longer and carries the risk of human error. As mentioned earlier, temperature control can be very demanding on the processor, and the PLC handling many other tasks at the same time can result in a slower response to process changes and therefore less accuracy than can be achieved with a dedicated temperature controller.

In process control applications, temperature controllers (thermostats) have several advantages over PLCs. They are faster to install and set up, faster and easier to operate, offer features dedicated to temperature control, and meet the high demands placed on process control because they are specifically designed for temperature control.

If the system requires a higher level of automation that cannot be achieved by a temperature controller (thermostat), then a PLC is a more reasonable solution, although it is still recommended to use a dedicated temperature controller to compensate for the lack of PLC in terms of temperature control. This allows for the use of specialized temperature control features and reduces the requirements for the PLC, eliminating the problem of slow response and large deviations from the set value, thus ensuring a high end product quality.

rkc thermostat – five advantages of thermostat over PLC

rkc thermostat – five advantages of thermostat over PLC

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