Design Procedure for HVAC Systems - Coursework Example

The Design Procedure for HVAC Systems Introduction In the contemporary era where computerized systems are essentially incharge of a variety of functions and role-play, the presence of HVAC systems cannot be ignored. HVAC as an acronym stands for – Heating, ventilation and Air Conditioning – vital in different arenas, in terms of application. Accordingly, the HVAC control system functions in terms of applying optimal regulation to either the air conditioning and/ or heating system present in a given environment. To be noted is that towards enhancing the basic operation and performance of the HVAC system, there is need for a ‘sub-system.’ Accordingly, the DDC– Direct Digital Control – system functions as the ‘brain’ behind existing HVAC systems. This is through its functional role-play of dictating the positions of all dampers and valves in a given system. Thus, it is able to aptly determine which of the existing HVAC system chillers, pumps and fans are effectively running and at what capacity, speed and/or rate. Ultimately, it is towards more efficient and effective automation that the DDC system is necessary. Existing groups of DDC controllers, whether networked or not, form a complete layer of system, thereby making it possible to link up various HVAC systems to a central control centre (Althouse, Turnquist, and Bracciano 14). HVAC Systems: Conceptual Analysis HVAC systems are comprised of various mechanical technologies, hardware and software components, all which efficiently work in a systematic ‘pre-programmed’ manner. HVAC in general regards to the pertinent technology vital towards both vehicular and indoor environmental comfort. Primarily, its ultimate goal is to provide not only acceptable indoor air quality, but also optimal thermal comfort (Bearg 108). Essentially, a sub-discipline of mechanical engineering, HVAC system design is based upon pertinent principles, i.e. heat transfer, fluid mechanics and thermo-dynamics amongst others (Bearg 109). Vital in the design and operational capacity of various medium to large-scale office buildings and industrial complexes HVAC is also useful in marine environments, i.e. aquariums. It aids in enabling healthy and safe building conditions, through regulation of both humidity and temperature by way of utilizing outdoor fresh air. This entails ventilation of the ‘indoor air’ in any given space, to be replaced by fresh, high quality air (Bearg 111). Thus, this involves varying aspects such as oxygen replenishment and temperature control, as well as the removal of existing moisture, smoke, dust, odors, heat, carbon dioxide and airborne bacteria (Egg 47). By removing excessive moisture and unpleasant smells, ventilation introduces outside air, in addition to preventing stagnation of existing ‘interior’ air and in keeping the ‘indoor’ air circulating. Accordingly, this process entails both the circulation of available air within a building as well as the exchange of air to the outside environment (Egg 48). The three core functions of ventilation, heating and air-conditioning are all interrelated, especially concerning providing acceptable indoor air quality, as well as optimal thermal comfort (Egg 50). This is within reasonable maintenance, operation and installation costs, with such HVAC systems being able to reduce air infiltration, provide optimal ventilation and maintain pertinent pressure relationships between the spaces present. Through ‘room air distribution’, HVAC systems are able to both remove and deliver air to such spaces (Egg 51). Criteria for an Optimal Quality HVAC System The ultimate goal of having a HVAC system installation is to aptly provide proper, efficient and effective heating, cooling and air flow to all areas within a given building. Accordingly, a quality HVAC system needs to aptly measure up to a set of core criteria. These aid in not only describing what entails a quality system, but also examine the question of key installation and design considerations; which ought to be met in order to achieve the goal of a quality system (Swenson 35). A HVAC system needs to attain the following conditions be properly sized to provide the correct airflow rate in addition to meeting room-by-room calculated cooling and heating loads and have a properly sealed supply ductwork, which will provide adequate/ proper airflow. It should also be installed within design and manufacture specifications, in terms of the static air pressure drop across the handler, and be installed with the requisite return systems that are adequately sized in order to effectively provide the correct return air flow (Haines and Michael 37-39). In addition, the system needs to have a proper draft and burner operation, be optimally charged with refrigerant, optimally minimize duct air temperature loss or gain between room registers and the air handler as well as between the air handler and return registers. It should also have balanced air flow between return and supply systems essential towards maintaining neutral pressure, and have sealed return ductwork, which is essential in providing optimal air flow to the fans, as well as avoiding ‘polluted air’ from entering the HVAC system (Haines and Michael 98). Procedural Design and Installation of HVAC Systems In order to correctly design and subsequently install HVAC systems, having ensured not only comfort and efficiency, but also the overall cost effectiveness; there is need for a set procedure. This is in terms of system design and subsequent installation, which is principled around the area or environment of installation. Accordingly, the following phases should be followed in both the design and installation of such systems, which include the need to determine room-by-room airflows and loads through use of ACCA Manual J circulation procedures. Others include the layout of duct system on the building’s floor plan in addition to accounting for the overall direction of roof hips, joists and firewalls amongst other potential obstacles (International Code Council). This is through determining register types and locations, as well as connections and duct lengths required in order to produce the required layout; considering the existing construction constraints. There is need to ‘size’ the duct system according to pertinent ACCA Manual D calculation procedures, as well as ‘sizing’ HVAC equipment to sensible loads through use of ACCA Manual S procedures (California Energy Commission). In addition, the ducts and equipment need to be installed according to set design specifications, utilizing installation procedures and requirements from the SMACNA, the Air Diffusion Council, the Uniform Mechanical Code and manufacturers’ specifications (Swenson 40). Through use of such procedural measures, the ‘set’ duct system ought to be airtight substantially. The installed system should be charged appropriately, in addition to verifying the charge by way of the sub-cooling or evaporator superheat methods (Swenson 42). Furthermore, there is need to check for proper firebox drafting and furnace burner operation, and the testing of the installed system with the aim of ensuring that it properly performs its functions (Swenson 42). This is achievable by way of determining that there is proper ‘sizing’ of the system and little or no leak at all. In addition, the system needs to be checked if it has proper plenum static pressures or proper air handler fan flow; or that there is proper plenum static pressure and optimal return air and room flows (Swenson 44). HVAC Systems: Design Procedure It is essential to have a duct installation system, which is considerably airtight and which provides optimal airflow to each room in a given space setting. Accordingly as presented by the California Energy Commission, issues of concern include the fact that the fittings, plenums and ducts need to be constructed of duct board, flexible duct or galvanized metal. Pertinent building cavities need either a metal liner or a sealed duct board in order to be effectively utilized as a plenum or a duct. The existing air-handler box needs to be air tight; with air filters and evaporator coils needing to be easily accessible (essential for replacement and cleaning procedures). The ducts should be both supported and optimally configured in order to amongst others: prevent the constriction of ducts below the set/rated diameter, prevent damage or dislocation, and prevent usage of excess materials. Furthermore, flexible ducts need not to have bends, which exceed 90o unless if specified within the design, the sheet sleeves and metal collars also need to be beaded in order to hold draw-bands. In addition, the flexible duct bends should not have incidental contact with existing pipes, conduits or metal fixtures or be made across sharp corners (so as to avoid either damage or compression of the present ductwork (California Energy Commission). The HVAC system design hence requires amongst others: first, CFM and Loads Calculation (with total room loads for determining pertinent system requirements, and the calculation of both heat gain and loss for each room; as stipulated in the ACCA Manual J Load Calculation). Secondly, the Lay Out Air Distribution System – the laying out of duct system on floor plan, and determining duct paths and register position essential in both minimizing actual duct length, equivalent length of bends and fittings, as well as optimizing room air circulation. Duct paths also need to be planned in order to avoid sharp turns that kink the duct, and that the duct paths need to account for both the directions and locations of roof hips, firewalls and joists, amongst other potential obstacles (International Code Council). Thirdly, there is need for use of the ACCA Manual D Duct Design, which aids in calculating the correct cfm for each room as well as the overall total for the whole building (in terms of both air return and supply) and the choosing of registers vital towards optimizing duct static pressure and air distribution. Others include the calculation of minimum return filter area (per ACCA methods for return-filter grills), the location and sizing of returns essential in optimizing air flow per ACCA methods, and that the ducts should be sized according to final layout (on plans), Manual D air flows and Manual J loads (Haines and Michael 374-76). Finally, the selection of the system should aptly consider that the equipment should be optimally sized to sensible loads; such equipment sensible capacity needs not be more that 15% larger than the overall total sensible design load as specified in Manual S and appropriate equipment be determined from both Manual D cfm and Manual J loads. It should also consider that the requirement of an equivalent, or the ACCA Manual S Residential Equipment selection (Haines and Michael 381). Conclusion Through stringent follow-up and observation of the aforementioned procedures, measures and regulations, the design, modeling and subsequent installation of HVAC systems can be effectively carried out. There is need for consideration of the various ACCA manuals that are pertinent to the effective functionality of any HVAC system; taking caution to ensure that there is compatibility, optimal communication and integration with the installed HVAC control system present. Works Cited Althouse, Turnquist, and Bracciano. Modern Refrigeration and Air Conditioning (18th Ed.). Goodheart-Wilcox Publisher, 2003. Print. Bearg, David W. Indoor Air Quality and HVAC Systems. New York: Lewis Publishers, 1993. Print. pp. 107–112. California Energy Commission. Procedures for HVAC System Design and Installation. California Energy Commission, 2015. Web. 13 Feb 2015. Egg, J. Geothermal HVAC: Heating and Cooling. United States of America: McGraw-Hill Companies, 2011. Print. pp. 45–62. Haines, Roger W. and Michael E. Myers. HVAC Systems Design Handbook, (5th Ed.). New York, NY: McGraw-Hill Education, 2009. Print. International Code Council. International Mechanical Code (1st Ed.). Thomson Delmar Learning, March 6, 2006. Print. Swenson, S. Don. HVAC: heating, ventilating, and air conditioning. Homewood, Illinois: American Technical Publishers, 1995. Print. Read More