Your questions answered: How to incorporate controls into HVAC systems

HVAC systems and their controls have continued to advance

By Consulting-Specifying Engineer April 13, 2022
Courtesy: CFE Media

The design of controls for HVAC systems is generally based on the design engineer’s philosophy and experience level. The audience should understand that the HVAC system itself, its controls components and the building in which it is installed should all be considered together as parts of a single, whole design.

Several questions were answered during the March 31 webcast on “How to incorporate controls into HVAC systems,” and additional answers are from:

  • Jason Gerke, PE, LEED AP BD+C, CxA, principal, MEP group leader, GRAEF, Milwaukee
  • Mike Click, CBCP, principal, Affiliated Engineers Inc., Chapel Hill, North Carolina

What is ASHRAE Guideline 36?

Mike Click: ASHRAE Guideline 36: High Performance Sequences of Operation for HVAC Systems is an attempt to help reduce engineering time, programming, and installation by providing standard practices for HVAC digital control systems. This standard provides uniform sequences of operation for HVAC systems that are intended to maximize energy efficiency and performance.

What applications are best for ASHRAE Guideline 36?

Jason Gerke: ASHRAE Guideline 36 continues to be updated with new addenda on a regular basis. The guideline started out with simple sequences for air handling units with chilled water and hot water. The updates, through addenda from what I have seen, continue to standardize sequences for additional equipment. It is recommended that designers regularly checkout the latest version of the guideline and watch for new addenda. The addenda are free to download through ASHRAE membership.

What Wi-Fi security standards exist?

Mike Click: I am by no means an expert when it comes to Wi-Fi security standards, but what I can share with you is that there are some things that you can investigate for this.

IEEE 802.11 is the security standard. WEP, or wired equivalent privacy authentication was somewhat derived from this standard. From my research this is really one of the weakest forms of authentication for access to a network.

The next is WPA, or Wi-Fi protected access, which uses a more robust form of authentication. Security weaknesses were found with WPA so around 2000 they put out WPA2.

Today we have WPA3, which was released around 2018. This was a replacement for WPA2 and uses 192-bit encryption opposed to the 128 bit that was used for WPA2.

Today WPA3 is the security standard that you would want to stick with moving forward if possible.

Courtesy: CFE Media

Is building automation system (BAS) and building management system (BMS) interchangeable terminology?

Jason Gerke: Yes, for the purposes of this presentation and commonly in the marketplace based on my experience, the terminology is interchangeable. It is important to note there may be a difference in the meaning of this terminology to owners, vendors, manufacturers and designers.

Under what circumstances do greenfield projects benefit from having a BAS vendor being selected during design development?

Mike Click: In my opinion it might be a little early to have the controls contractor on board during design development however, I do encourage projects to look at opportunities to bring them in early. Some of the benefits include:

  • Assistance in comprehensive and detailed controls sequence of operations.
  • Cost control on equipment with the ability to be thoughtful when it comes to having a quality device in the field versus a standard field instrument.
  • Further understanding and details of how the controls and execution of the controls will be accomplished in the field.
  • Lastly, a good understanding of all required hardware and software points.

Who should lead the building’s platform for controls throughout the building?

Jason Gerke: The appropriate leader for identifying opportunities and leading the design effort is the person with the most experience in this system. This could be the mechanical engineer, a control engineer or even a vendor/manufacturer if subcontractors are onboard early in the design phase. The important action by the leader of this process, whoever they are, is to ensure that all parties are heard, all options are explored and the entire team (design, construction and owner) are onboard with the process and have buy-in to the goals.

Which BAS systems do you specify most: wired or wireless control systems?

Jason Gerke: It is common for our team to see wired control systems on projects or at least partial wired systems. Manufacturers offer a number of options for full wired to full wireless controls. The most common solution we see on school renovation projects is wired solutions to the main equipment and wireless thermostats/temperature sensor devices in the space. Another solution that is very common in office buildings is wired thermostat/temperature sensors to variable air volume boxes and a wireless mesh network from that point to the head-end BAS.