Questions and answers: Best practices for implementing BACnet protocols

• Analytics tools can help demonstrate the faults of a connected system.
• Costs and lack of knowledge can be the most significant impediments to implementing a BACnet system.

Expert presenters from the “HVAC and BAS: Can BACnet control an HVAC system?” webcast answer audience questions. Watch the on-demand version of the webcast here.

Presenters:

• Yanlin Zeng, PE, CEM, CMVP, LEED BD+C, Controls Engineering Supervisor, Southland Industries, Dulles, Virginia

• Jason Gerke, PE, LEED AP BD+C, CxA, principal, GRAEF, Milwaukee

What are the main impediments to implementing BACnet protocols in a project?

Jason Gerke: Well, there’s a few of them. The first one and probably the most important one may be cost. Cost helps us make decisions on a lot of projects, sometimes decisions that we don’t want to make. Another impediment could be the capabilities or knowledge base of the people on the project team. This could be the design team, the contractors or the owner concerned about implementation of something that they’re not completely comfortable or knowledgeable about.

Another impediment could be the unwillingness of the team to commit to a specific protocol and system which could potentially limit some decisions in the future on types of equipment, could limit some opportunities for cost savings in the future. It could create some restrictions in future decisions, but create the baseline and create a decision-making process for some of those decisions.

What commands do you typically send to chillers, heat pumps or boilers? Is it just a setpoint or what do those look like?

Yanlin Zeng: Normally, we will enable/disabled the chiller or the boilers. Also, we’ll send subpoints for the chiller boiler to maintain. Also, we monitor the chiller status and the chiller alarm because we believe those are critical points. If we lose communication with enable signal, with the status, alarm and the subpoint, the system still can be run properly.

What needs to be done or what factors need to be considered to add analytics tools to an existing building automation system (BAS)?

Jason Gerke: Adding analytics to a system, some of the same similarities to the impediments to adding BACnet in the first place on a project or committing to BACnet apply. When it comes to analytics, you need to make sure that you’re going to use it. Do you know how to use it? Do you have a way to implement it once you get the information? We all have more information than we know what to do with, in our personal lives, and probably for sure at work.

Your internet browser knows what you like. Microsoft Word knows the next word you’re going to type. We just need to be prepared what to do with all this information and how we can utilize it. It will give us some great tools, but it is going to require somebody to manage it.

Managing it doesn’t need to necessarily be a day-to-day operation, maybe it could if it’s a big enough facility, but we need to be prepared to handle this data and then do something with it. The last thing that anybody wants to have happen is look back after something bad happens and say, “Oh yeah, we knew this was going to happen.” Nobody wants to explain that to their supervisor.

Is SCADA a part of BAS or is it an individual entity on its own?

Yanlin Zeng: SCADA stands for supervisory control and data acquisition, and this is not part of the (BAS). Most of the time we see the BAS, we mostly use them for commercial buildings on the heating, ventilation and air conditioning (HVAC) system. SCADA is more used for secured systems, also including electrical equipment. But sometimes those two will be independent of each other. Sometimes we do connect them together. It depends on the client’s requirement.

Regarding remote access, have you had any experience with hackers gaining access to BAS and possibly causing building damage?

Jason Gerke: I do not have direct experience with that, but there absolutely is a risk for someone accessing your building control system from the outside or getting through a firewall that may be of different quality than a firewall that your own company may have, but may very similar. We need to think about what systems we connect to this overall building automation system control network.

We could connect everything if we wanted to. We don’t connect it sometimes because of complication or cost, but we also may choose not to connect it based on security and bad things that could happen if an unauthorized person got access to the system. I think those are all some things to consider when we’re thinking about how much and how many things are we connecting to a central control system and what is the security that’s being managed to protect that system.

Is it normal for BAS and BACnet controllers to have backup power in case of power outages?

Yanlin Zeng: It really depends on the system the controller is controlling. For example, if the controller is controlling the air handling unit serves a critical space, then yes, we do want the uninterrupted power supply as backup or even the whole panel on the generator. But if this unit is only just serving like a storage area, it’s not really a big deal if you lose some time without power. And the controller lasts 72 hours, so a So, if something is running, it will just keep running. It has no way to shut it down unless you go personally go through the starter and turn off the fan. There’s no universal answer, it just depends what system you’re controlling.

Talking about sequences of operations, coordinating it with the contractors, do you have any suggestions or tips for that?

Jason Gerke: As far as coordinating to make sure that once we write a sequence, how do we make sure that as a designer we get that at the end of the project? Contractors, we all know, have their own kind of language that we may see in submittal, so we need to review that closely. Then, another important thing to incorporate on the project is potentially commissioning, which will ensure that there’s a third-party person that makes sure that happens. All these would be steps to make sure that we have a successful integration of different components on a control system and are really important to make sure that the owner’s getting what they expect, the designers getting what they specified and that it’s a successful outcome we don’t all have callbacks.