Choosing an HVAC vendor is one of the most important decisions a building owner makes. For items such as vents and fittings the choice is simple; but when it comes to managing HVAC, a big factor in the selection process is whether that vendor offers a proprietary system or one with open controls. This may seem like a simple one-or-the-other choice, but it’s a complex matter.
Proprietary HVAC controls are found in systems that are manufactured by one vendor using protocols specific to that provider. The makers of these systems will tell you that they are superior because every piece of your building automation system (BAS) comes from a single source. With a single vendor ensuring that everything runs smoothly – from installation to ongoing maintenance – building operators will, they say, get a better product.
Open controls use open protocols that can be used by anyone. Proponents of open protocols claim that open systems offer ease of integration, more vendor options and less expensive upgrades. Ease of integration, which is also known as interoperability, means that the HVAC system can communicate with components of the BAS such as lighting and security.
Consumers want the benefits of smart home features, so integration is more important than ever. Manufacturers of proprietary systems are aware this, and some are pairing up with lighting companies and security firms to offer integration options. Many are also developing systems with open protocols.
Integration and Legacy HVAC
Proprietary control use is declining quite rapidly, but you can expect to see proprietary controls in legacy HVAC systems for a long time to come. In 2003, proprietary systems still had the lion’s share of the market, but by 2014 IHS reported that only 14.2% of worldwide controllers still used proprietary protocols.
You can integrate legacy systems with products that act as a communications gateway. These gateways don’t really solve the problem of interoperability, they just add another layer of management. For example, if the HVAC system using proprietary controls undergoes a major software update, the gateway will also need to be updated. That can become pricey.
How to Avoid Proprietary Controls
If you want to go with open controls, your best bet is a system that uses either the BACnet or LONWORKS protocol.
BACnet has interesting features that allow vendors to use some proprietary programming. Basically, the BACnet protocol determines how devices and systems communicate with one another. The language of each individual system is irrelevant. In Fundamentals of HVAC Control Systems (Elsevier), authors Ross Montgomery and Robert McDowall compare this to two people speaking English to one another while one of them thinks in Spanish and the other in French. Their native languages aren’t compatible, but they speak in a common shared language.
LONWORKS products are often “plug and play,” meaning that no configuration is required, whereas BACnet products generally need to be configured. LONWORKS products can also be configured if the project requires this.
The subject of configuration leads to one final complication: an open protocol doesn’t always result in a seamless integration. There is more than one way to configure open protocol devices, so HVAC, lighting and security systems can all use the same protocol but be inoperable due to incompatible configurations.
As mentioned earlier, it’s a complex choice. Open protocols seem like the best option, but proprietary controls offer the advantage of a clear responsibility for system functions. Busy building operators may decide that the ease of making one call when the system goes down outweighs all other factors.