High Performance Sequences of Operation for HVAC Systems
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ASHRAE Research Project 1455 developed the sequences of operations that formed the basis of GPC-36’s first deliverable. RP‑1455 produced 5 deliverables:
Task 1, Background Literature Survey: A background literature survey of published sequences of operation, including but not limited to:
Sequences being used by major control manufacturers, a sampling of consulting engineers (e.g. current and past TC 1.4 members), and published work. The emphasis shall be on sequences that optimize both comfort control and energy efficiency.
Sequences required or recommended by standards, codes, and guidelines such as ASHRAE 90.1, ASHRAE 62, ASHRAE Guideline 16, California’s Title 24, USGBC LEED™, and model codes
Sequences shown in recent studies to be energy efficient, such as those in the Advanced Variable Air Volume System Design Guide
Diagnostics and alarms that could easily be programmed into control logic to provide realtime fault detection and diagnostics (RTFDD)
Task 2, English Language Sequences: These had the following objectives:
The contractor shall merge the best features (in the opinion of the contractor with review by the PMC) of sequences found during the background phase or developed in-house plus additional sequences required to address energy and indoor air quality standards and RTFDD into a comprehensive set of optimized control sequences for the systems and subsystems listed below. The energy effectiveness and overall performance of the sequences is to be based on the research from Task 1 plus the experience of the Contractor team; the actual effectiveness will not be tested as a part of this project. Sequences shall be general and flexible so that they can be applied to many common HVAC applications, but they shall be arranged or modularized so that if a certain component is not included with a specific system (e.g. no heating coil) it can be easily removed.
The level of complexity and sophistication of the sequences shall be a balance of performance (energy efficiency, reliability, etc.) and usability (ease of understanding). The sequences are intended to be implemented in common DDC programmable controllers. Thus the limitations of these devices with respect to programming memory shall be considered, although it is not intended that the sequences be designed to work with all available DDC systems.
Sequences shall be annotated to explain the reason behind the control logic. The intent is to help engineers who are editing the sequences for their projects understand the rationale and underlying technical basis for the sequence. Annotations shall be in a separate style or font so that it is clear they are not a part of the sequence and to allow the annotations to be easily removed.
Features listed below shall be at a minimum addressed in control sequences. A control schematic shall be created for each system. Only control points used for control logic shall be shown (or those for monitoring only shall be distinguished in a manner that makes it clear they are not required).
Alarms must define alarm parameters (alarm setpoints as a function of mode, differential, escalation, etc.) and suppression logic to avoid nuisance alarms (e.g. time delays, delays on changes in operational mode or setpoint, interlocks to system status, etc.). RTFDD must include both automatic self-diagnostics and user-initiated diagnostics. Sequences shall be included in a Task 2 report and submitted in electronic pdf format to the PMS for approval prior to proceeding to the next task.
The RFP specifically listed a number of components and systems.
Task 3, Logic Diagrams:
For each element of the Task 2 sequences, corresponding functional logic diagrams from a manufacturer’s control program were developed. This functional logic was tested in real control hardware in Task 4 through simulation. The GPC 36 Committee considered publishing these logic diagrams but decided not to at this point as they only represent one manufacturer’s implementation of the RP 1455 sequences.
Task 4, Implementation and Simulation: The intent of this Task is to ensure that sequences can be implemented in an existing DDC system and that sequences are fully debugged and meet the intent of the English language sequences. The intent is not to simulate against a model of a real building or real HVAC systems; application specific tuning parameters such as loop gains, timing intervals, etc. are not intended to be determined by the simulation. The intent is also not to prove that sequences are energy efficient; it is expected that the performance of sequences will be ensured by the experience of the Contractor team who create them. Later research projects will be developed to field test sequences.
Task 5, a final report of the findings.
In addition to RP-1455, Technical Committee 1.4 has sponsored several other related research projects that are of interest to Guideline 36:
RP-1547, CO2-Based Demand Control Ventilation for Multiple Zone HVAC Systems. This project was intended to develop a method for dynamically solving the Multiple Spaces Equation from ASHRAE Standard 62.1 in real time. It was completed in September of 2013 but was not included in RP-1455 as it ran in parallel, and it did not develop comprehensive sequences for all of the systems in RP-1455. A follow up research project, RP-1747 has been sponsored to develop that logic.
RP-1746, Validation of RP-1455 Advanced Control Sequences for HVAC Systems – Air Distribution and Terminal Systems. This project has two main objectives:
Develop complete step-by-step functional performance test scripts for each sequence in RP-1455 and validate the tests by performing them in a typical commissioning environment. These test scripts are intended to be used by DDC system manufacturers to verify their own implementation of the RP-1455 sequences and also by commissioning agents validating BAS programming in the field.
Operate the systems under real-world operating conditions in the testing facility, collect trend data with the DDC system, then analyze the using post-processing tools to verify that sequences are properly programmed and operating stably.
RP-1747, Implementation of RP-1547 CO2-based Demand Controlled Ventilation for Multiple Zone HVAC Systems in Direct Digital Systems. This project builds on RP-1547 to develop control sequence logic that implements the dynamic recalculation of the Multiple Spaces Equation from ASHRAE Standard 62.1. The results of this project are intended for inclusion in a future version of GPC 36. It has been approved for bid in spring of 2015 and is scheduled for completion in 2017.
RP-1587, Control Loop Performance Assessment. This project is complete. It developed a metric for control loop performance.
RP-1711, Advanced Sequences of Operation for HVAC Systems. This is a “wet-side” analog of the RP-1455 project. It is scheduled for bid in the Spring of 2016.
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