ASHRAE Guidelines for High-Performance Sequences of Operations for HVAC Systems

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ASHRAE Guideline 36-2018 was created as a way to put out best practice control sequences that make complying with other ASHRAE standards easier. Intended for use in systems that contain modern-day equipment like VFDs and fully-programmable control systems, it gives HVAC designers, commissioning agents, control contractors, and building owners, operators, and maintenance technicians best in class control sequences that help yield high energy-efficient buildings.

ASHRAE Guideline 36-2018 Amendments

In addition to helping maximize an HVAC system’s energy efficiency and performance, ASHRAE 36 was designed to provide better control stability and facilitate real-time fault detection and diagnostics in variable-air-volume, or VAV systems.

Though there have been newer system types created in an effort to surpass the energy efficiency and comfort control performance of VAV systems, “a well-designed VAV system using the latest ASHRAE guidelines is often the more energy-efficient and cost-effective system available” says SFC’s VP & Principal, Christopher Ramos.

Since it was released in 2018, nine amendments have been added to the guideline, the latest one released in January 2020.

  • Addendum J revises the zone ventilation control logic in the guide’s Section 5.2.1.4. that covers compliance with California’s building energy efficiency standards.

  • Addendum I revises the way variable-speed series fans are controlled.

  • Addendum G made numerous small changes to multiple sections of the guideline, including some deletions.

  • Addendum F addresses issues with air-flow differentials.

  • Addendum E implements ASHRAE Standard 62.1 and 90.1 addenda to allow minimum rates to be automatically calculated.

  • Addendum D updates the description of the minimum heating airflow set point and revises damper control information.

  • Addendum C revises VFD minimum speed read/write to reduce network traffic.

  • Addendum B replaces the section covering control standards for Trim & Respond.

  • Addendum A addressed issues with controllable minimums.

Enhanced Building Operations

As technology integration between all of a building’s systems creates smart building operations, how important a good network infrastructure and BAS are to the process cannot be overstated. Even for buildings that’s aren’t completely smart, the use of networks is often extensive.

Standardized advanced control sequences as provided by ASHRAE 36-2018 provide significant benefits such as:

  • Reduced engineering time

  • Reduced programming and commissioning time

  • Improved indoor air quality

  • Reduced energy consumption

Perhaps most importantly, a common set of terms makes communication between specifiers, contractors, and operators more efficient.

Moving Forward

The building industry is always looking for ways to improve the performance and reliability of HVAC equipment and controls while reducing the burden of commissioning systems to support performance. Some of the most significant barriers to achieving performance goals have been:

  • A lack of industry standards for control systems logic.

  • The common practice of each application having a custom logic.

  • Operational problems that are not fully debugged because of programming costs.

  • Poorly documented control systems.

ASHRAE Guideline 36-2018 was created with the belief that high-performance buildings will see significant improvements if an established sequence of operations is specified and controls contractors design and refine products to correctly implement them. Because it greatly simplifies the design of high-performing systems, designers can now specify that all system control sequences be in accordance with the guideline. And there’s no need to consider controllable minimums with respect to airflows as the guideline fully addresses the issue.

The guide’s standardized advanced control systems help reduce the cost of designing and installing control systems, reduce maintenance costs through automatic fault detection, and improve HVAC system thermal comfort and energy performance. That makes Guideline 36 a true win-win-win for the building industry.

Christopher Ramos