ASHRAE Guideline 41 2023
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ASHRAE Guideline 41-2023 — Design, Installation and Commissioning of Variable Refrigerant Flow (VRF) Systems
Published By | Publication Date | Number of Pages |
ASHRAE | 2023 |
Guideline 41 was developed by ASHRAE to provide information and guidance relating to the design, installation, and commissioning of variable refrigerant flow (VRF) systems. The guideline is intended to expand on the basic information currently provided in ASHRAE Handbook HVAC Systems and Equipment, Chapter 18, Variable Refrigerant Flow. In particular, enhanced guidance is provided on installation, commissioning, start-up, and operation. The 2023 edition of the guideline includes the following key updates: * New guidance for modeling an HVAC system that includes variable-refrigerant-flow (VRF) equipment * Clarification of how the VRF internal system controls work both as stand-alone and when interfaced with third-party automation and controls systems and devices * Additional commentary on proper methodology for complying with outdoor ventilation requirements when using VRF systems * Updates to climate zone and seismic survey maps For a full list of changes in the 2023 edition, see Informative Appendix A.
PDF Catalog
PDF Pages | PDF Title |
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1 | ASHRAE Guideline 41-2023 |
3 | Contents |
4 | Foreword 1. Purpose 2. Scope 2.1 This guideline provides the procedures and design factors a design engineer should consider; the requirements and installation factors the installing contractor should consider; and the performance, commissioning, and operational factors the cont… 2.2 This guideline is intended for use with nonresidential building systems (including, but not limited to, hotels, office buildings, hospitals and other health care facilities, assisted living facilities, schools and universities, commercial buildin… 2.3 This guideline is intended for use by design engineers, installing contractors, owners, operators, users, maintenance personnel, and equipment manufacturers. 2.4 This guideline applies to the design, installation, and commissioning of VRF in new buildings, and to the retrofit and renovation of existing buildings. 3. Definitions and Symbols 3.1 Definitions |
8 | 3.2 Abbreviations and Acronyms |
9 | 4. Variable Refrigerant Flow Overview 4.1 General. Variable refrigerant flow (VRF) systems are a useful and unique addition to the HVAC industry. Two key new features are the inverter-driven, variable-speed compressors that are the heart of the system and the capability to include as man… |
10 | 4.2 VRF System Layout. Figures 1, 2, and 3 show typical VRF system configurations. 4.3 Develop Commissioning (Cx) Process and Plan. When a VRF system is installed, the following should be considered as part of the Cx Process and Cx Plan. |
12 | 5. Feasibility for VRF System Design |
13 | 5.1 Occupancy Classification. VRF systems can effectively serve the needs of the following occupancy classification types, as they offer zone-based distribution control, provide variable capacity, can be applied in low-sound applications, facilitate … 5.2 Type of Climate and Considerations. The United States is divided into seven major climate zones by ANSI/ASHRAE Standard 169 11 (Figure 4). In the rest of the world, additional climate extremes will impact building design and HVAC system selection… |
15 | 5.3 Type of VRF Systems. VRF systems are described in ASHRAE Handbook—HVAC Systems and Equipment 4, Chapter 18. There are two basic choices in the type of VRF system: heat-pump or heat pump with heat recovery. The systems may also be either air-to-… 5.4 Building Control. When designing building controls, the following issues should be considered: 5.5 Life-Cycle Cost Analysis (LCCA). LCCA is a tool to determine the most cost-effective option among different competing alternatives to purchase, own, operate, maintain, and dispose of an object or process, when each is equally appropriate to be im… |
16 | 5.6 Refrigerant Use Restrictions. VRF systems are classified as direct systems by ASHRAE Standard 15 2, meaning that the conditioned air passes directly over or through system components that contain refrigerant. 5.7 Refrigerant Leak Fault Tree Analysis. A fault tree analysis of the installed HVAC systems and component placement should be prepared in order to minimize the potential of refrigerant leaks into the conditioned space. 5.8 General Piping Consideration for VRF Systems. When designing or installing VRF systems, the following considerations should be made: |
17 | 5.9 Ventilation Factors |
20 | 5.10 Building Control Levels. Figure 9 shows the level of controls that are available when using a VRF system. There are four levels of controls for VRF systems: 5.11 Applicable Codes and Standards. The list below represents the potential range of codes and standards that could impact VRF system design and installation: |
22 | 6. Design for VRF Systems 6.1 General Considerations for Variable Refrigerant Flow (VRF) Outdoor Unit (ODU) Systems. The following should be considered for VRF ODU Systems: |
23 | 6.2 Specific or Special Considerations for VRF Systems. The great flexibility of VRF systems for addressing loads in the building Design Phase creates a challenge for the designer to combine indoor units (IDUs) into systems that provide the best scen… |
24 | 6.3 Determine VRF System Type and Format. This section reviews the types of VRF systems, when they should be used, and when to apply different operational modes. |
25 | 6.4 Low Ambient Cooling and Heating. This section reviews VRF system optimization when low ambient cooling and heating is used. |
26 | 6.5 System Sizing. The designer should address the following factors when sizing the components of a VRF system: 6.6 Ventilation Requirements. When determining the ventilation for VRF systems, the following should be considered. |
27 | 6.7 Refrigerant Management. When assessing the management of refrigerants for VRF system design and layout, the following should be considered. |
28 | 6.8 System Controls. The installation of a complete system of manufacturers’ controls is required for a VRF system to work properly. VRF systems are just that, a system, not applied components like dampers, fans, or coils. That said, various levels… |
29 | 6.9 Piping Design and Layout |
32 | 6.10 VRF System Electrical Considerations. The following electrical design considerations should be reviewed for VRF systems. |
33 | 6.11 Other Design Considerations. The following are other topics that should be considered for VRF systems. |
35 | 6.12 Energy Modeling. Energy modeling is critical to the design and operation of low-energy, high-performance buildings and development of U.S. federal and state level building energy goals. Some of the key factors to consider in modeling the variabl… |
36 | 7. Installation Phase 7.1 Submittal Review. Perform reviews of coordination drawings, shop drawings, and equipment/system submittal data sheets to check the systems for consistency with construction documents. Factors to review include the following: |
37 | 7.2 Contractor Training. Contractor specific training requirements should be written into the project specifications with the following considerations. Every manufacturer may have different installation and commissioning (Cx) related training require… 7.3 Placement Considerations for VRF System Components. The following should be considered when placing VRF system components during installation. 7.4 Piping. The following should be considered during installation of pipes for VRF systems. |
42 | 7.5 Refrigerant. The following should be considered while charging refrigerant in VRF systems: 7.6 Electrical. The following electrical considerations should be accounted for when installing VRF systems. 7.7 Controls. The following should be considered when selecting and installing controls for VRF systems: 7.8 Quality Control Considerations for the Construction Phase. The following quality control considerations should be accounted for when installing VRF systems. |
43 | 8. VRF System Start-Up, Commissioning, and Operations 8.1 Develop Prefunctional Checklist and Functional and Performance Testing Procedures. A prefunctional checklist should include the following. 8.2 Start-Up, Functional, and Performance Testing. The following testing procedures should be followed to verify proper system operation of VRF systems. |
45 | 8.3 Training for O&M Staff. When preparing training for O&M staff, the following should be considered. 8.4 O&M Plan. When preparing the O&M plan, the following should be considered. 8.5 Commissioning Report. The final Cx Plans and all testing results should be included in the project preliminary and final Cx Reports. See ASHRAE Standard 202 5 and ASHRAE Guideline 0 6 for additional information on the contents and assembly of the… 9. Normative References |
47 | Informative Appendix A: Addenda Description |