The Simatic S7-1200 and Simatic Basic Panels are the new automation standard in the compact class at KKT Kraus. The cooling and air-conditioning technicians will use them in future to control the larger part of their innovative cooling and energy saving systems. A new feature is the “energy saving meter” which displays the saved energy, the CO2 equivalent, the amount of costs saved and the exact amortization time of an energy saving system.

The KKT Kraus Kälte- und Klimatechnik GmbH in Lauf near Nuremberg, Germany, today part of the Swiss Schulthess Group with about 200 employees, has been active in its field for more than thirty years and specializes in very energy-efficient, environmentally friendly system solutions. One example of this are KKT’s fast coolers for so-called eutectic packs which have established themselves as an economical alternative to dry ice in the transport of refrigerated goods. The fast coolers return the cooling packs to the necessary core temperature after use within a maximum of 10 hours. They have redundant process and control structures and are available in two sizes. Both with two totally separate cooling circuits consisting of an evaporator and a fan assembly. This always ensures emergency operation of one of the cooling circuits if the other one has failed or is malfunctioning.

Fast cooler with cooling pack (All photos: KKT Kraus GmbH)

Reliability counts

Frequent problems with the originally installed controllers of another manufacturer led the company to respond quickly when Siemens presented the Simatic S7-1200 compact controller which exactly suited their price-performance class. More than 1,000 installed controllers of the Simatic S7-300 series, some of which have been operating reliably for more than 10 years, were an excellent reference. One CPU 1211C (fan) and one CPU 1212C (evaporator) will be controlling one cooling circuit of the fast cooler respectively in the future. Decisive advantages: The Siemens compact controllers are designed for ambient temperatures up to –25°C and can therefore be used in the immediate vicinity of the evaporator without any increased risk of failure. They control and monitor fans, defrost heating, door contacts, lighting and a traffic signal for indicating the operating states. The sensor technology (temperature sensors/transformers) is linked via the integrated inputs/outputs of the S7-1200 which provides the required temperature resolution of ±1 °C; additional I/O modules (signal modules) are not installed. Redundancy on the control side is achieved by coupling the two fan controllers via their integrated Profinet interfaces. A fast, simple method of networking which considerably reduces the wiring and installation expense especially since the two system sections are often installed in separate places. In order to create constantly identical conditions in commissioning, operation and local service, a standardized system structure was chosen and the fan controller was extended generally with a CSM 1277 Compact Switch Module, a 4-port Unmanaged Ethernet Switch. A Simatic KTP400 Mono PN Basic Panel (3.8 inch touch display with four tactile function keys) for setting and visualizing temperatures and switching times for both cooler circuits is connected. The Basic Panel can either be installed fixed in the switch cabinet front or be connected for service purposes only by the KKT technician.

The energy saving meter is implemented on a Simatic Basic Panel KTP1000 color PN for Marbach GmbH

Savings made transparent

The versatile combination of compact controller (in three performance classes) and Basic Panels (in seven variations) is now also used elsewhere. The people at KKT have also developed an “energy saving meter” as a (retrofittable) option to their established energy saving systems (ESS) for industrial cooling systems. The energy saving systems can be retrofitted without intervention in the existing controller and use the outside air for cooling. The main cooling system only has to run at full power when the outside temperatures are too high. This offers a potential saving of up to 80 percent depending on the system and usually amortizes itself in less than two years. “Proving” this is the job of the energy saving meter which continuously records all the operating parameters of the ESS and calculates and visualizes the savings for energy consumption (kWh), CO2 emission (tons) and operating costs (Euros) based on the current tariffs. The accumulated values since commissioning and since the last reset are displayed; in the latest version the opera tor can also store the investment costs. He can then see in black and white when the amortization time is reached and his ESS starts to “earn” money. It also demonstrates and communicates the company’s environmental consciousness to the public.

Energy efficiency confirmed in practice

Karl Marbach GmbH & Co. KG in Heilbronn, Germany, the leading system provider for tools for producing cardboard packing, is one of the first to do this. Marbach wanted to know how great the savings and thus the relief for the environment achieved by the existing KKT energy saving systems really are and be able to show this to interested customers. For this, the Simatic S7-1200 (CPU 1211C) was combined with a graphics-capable Simatic KTP1000 color PN Basic Panel (10.4” display, resolution 640 × 480 pixels). KKT has created a clear, graphically animated flow diagram of the process under cover of the Simatic Step 7 Basic engineering system which integrates the PLC and HMI environment. Shown are the cooling circuit, how much the ESS is currently contributing to the cooling and the above mentioned savings. Another screen shows all the measured values, user-defined settings and the savings in detail.

Marbach was so impressed by the energy saving meter and the simple traceability of the energy savings from the very start that they also wanted to use it in a new cooling system with an energy saving system from KKT Kraus at their Geyer site. They also took the opportunity to transfer the control of all the energy saving system’s components to a Simatic S7-1200 (CPU 1212C) and chose the lower cost version of the energy saving meter with a KTP400 monochrome Basic Panel. The energy saving meter rapidly gets closer every day to the break-even point of amortization at which the system saves money. The developers in Lauf have designed an energy saving meter for simulation operation to make it easier to choose one of their energy saving systems: a portable box with Simatic S7-1200, Simatic Basic Panel and all the necessary system connections. The simulator can be borrowed and the possible saving potential examined on the cooling system.

Principle schematic diagram of a fast cooler: Simatic S7-1200 linked via Profinet maintains emergency operation in case of partial failures

Efficiently integrated engineering for PLC and HMI

PLC technician Frank Aschenbrenner of KKT Kraus described the introduction to the new, compact controller class from Siemens as intuitive and very simple: “The integrated engineering for PLC and HMI with Simatic Step 7 Basic virtually explains itself to an experienced programmer and the comprehensive online help does the rest.” The variables are automatically kept consistent. When something is changed in the HMI part, this is immediately taken into account in the PLC part and vice versa. The programmer from KKT prefers to work with two screens also on the laptop so that he can simply pull variables from one monitor to another, from the HMI to the PLC section, by drag & drop without having to create, search, copy and paste long I/O fields which includes always a certain error risk. Right from the beginning, he has also used the local and central libraries for saving and reinserting practically any elements of a program. All in all these aids usually save up to a quarter, sometimes even a third of the normal engineering time. The greater the HMI part of an application, the greater the saving so that the controller change is worth it not only for the user but also for the manufacturer.

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