What does bus communication mean at D+H?

Our greatest incentive in creating the ACB was to optimise the functionality, flexibility and cost-effectiveness of SHEV control systems. In close collaboration with experienced technical experts, we spent many months working intensively on the development and embracing the exciting challenge of taking communication between drives and control panels to the next level. The status quo on the market was that most systems only allowed communication using the polarity of the output voltage in one direction: from the control panel to the drives. Our goal here was to make the drives talk to the control panel as well. They should be able to communicate with the control panel – without extra wiring!

We needed to create a technology that both reduced the size of our control panels (because no building operator likes large control cabinets) and featured higher performance capacity. The goal was for the ACB to be compatible with the conventional polarity change standard while also offering considerable functional advantages when combined with D+H drives and control panels.

We launched the ACB technology in 2016 along with the digital, fully modular CPS-M smoke vent control panel. Compared to the plug-in control panel technology, the CPS-M requires less than half the space. One reason for this is that each module has two group connections as opposed to just one, and the modules are far more compact than the plug-in units. Another reason is that the Advanced Communication Bus connects the drives to the control panel using only one group connection and one cable. Using conventional technology required laying an additional cable and using an additional group plug-in unit for every window that needed to be separately controlled. Reducing cable routing and cutting down on the number of modules provides a major cost advantage for our customers.

The CDC-ACB chain drive and the ZA-ACB rack and pinion drive are equipped with the new technology. Other D+H drive models are already being converted. Thanks to improved communication, the window drives no longer just receive instructions from the control panel. They also return information to the CPS-M about their status, connections and position. In addition, each individual drive can now be moved to a specific position. This is called bidirectional communication, and it provides the user with more functions while also making it easier to carry out maintenance work because it is significantly easier to read out information from the drives. With the ACB, this communication can be easily configured via the controller. Using conventional technology, this had to be carried out at the window drive itself. This was usually complicated because the drives are installed in areas of the building that are difficult to reach. 

There are comparable technologies on the market that involve controlling drives from a control panel on a bus. These technologies differ greatly depending on the manufacturer. However, I see them all as having one thing in common: drive synchronisation and communication with the control panel take place on the same bus. In developing the ACB, we made a conscious effort to separate these two aspects from each other. Doing so has safety advantages and also allows us to individually control multiple synchronous groups on one ACB section. As far as I know, this is something that no other provider offers. Using conventional solutions here would mean either that only one synchronous group could be controlled on a group connection or that a separate bus cable would be required with an additional bus coupler for each synchronised group. Our solution integrates the bus coupler in the drives themselves. This way, 20 single drives can be controlled using one ACB section for SHEV, and as many as 32 single drives for natural ventilation.

Our ACB solution also means we are the only supplier to use an open protocol standard. This results in an entirely new field of application. As an example, building automation can directly control our drives individually and with perfect positioning for ventilation purposes.

Generally speaking, the term 'bus' in information technology refers to a system for transmitting data between multiple nodes in a network using a shared transmission path. The most important nodes in a SHEV and ventilation network are, in most cases, a building management system, the window drives and the control panels. Protocols are used as transmission paths to meet the requirements for system-internal, secure and stable communication. For the Advanced Communication Bus, this is based on the conventional Modbus RTU protocol. Why conventional? Over time, a wide variety of transmission systems have been developed by various manufacturers. On an international level, though, only some of these systems meet recognised standards. Modbus RTU is one of the protocols that meet international standards, qualifying it as an vital component within industrial communication. 

As far as the structure of the ACB is concerned, we need a cable with four wires for connecting ACB drives. Two wires are for the power supply and the other two are for communication. As usual, this allows wiring to be routed through all drives in series. Another advantage of the ACB is worth mentioning here. This design does away with simple cable monitoring. Instead, each drive or drive group is monitored directly, providing an additional degree of security. Now, a fault is reported, for example, if a drive cannot open a window due to mechanical problems and an overload is detected.

The D+H rack and pinion drive is the perfect solution for the roof area. Equipped with a rugged rack and pinion, it has high pressure stability, allowing it to drive heavy flaps, skylights and windows without any difficulty. Of course, the recent addition of the ACB to the drive's equipment does not change this feature. The ACB simply makes the drive intelligent as well as powerful.

It is very easy to identify the advantages of the ZA-ACB, one of the many variations of the ZA, which was designed specifically for louvre windows. In particular, having millimetre precision control plays a major role here. In the summer, you might want the louvres to create a small gap by opening up only 12.9 % of the way. Alternatively, you might prefer an 80 % opening for a strong breeze to air the building? To implement this control with perfect positioning, the conventional rack and pinion drive previously required a wide variety of additional plug-in units and control panels. Today, all you need is a system consisting of the CPS-M and the ACB-capable drives. This, along with the ability to connect drive groups using just one connection and one cable, provides tremendous cost advantages for the customer, especially in the roof area. Installation also becomes much simpler.

Another example can be used to highlight the advantage of the function that allows you to control the drives within a group individually. Imagine, for instance, multiple offices along a façade with windows that open when using SHEV but are to be controlled individually for ventilation purposes. In the past, this set-up required a group connection at the control panel and separate wiring for each drive. Thankfully, the ACB, along with a concept called virtual grouping, makes this complicated scenario a thing of the past. Just one group connection and one cable are needed for all offices.