HVAC System:
(1) Describe the components of the system or systems (AH, VAV, RTU, Chiller, cooling tower, piping, pumps, type of duct, etc.).
Direct Expansion Air Conditioning serves as the main system used for the HVAC system. This kind of system utilizes RVEC or refrigerant vapor expansion/compression cycle to allow for the direct cooling of the air supply to an occupied space. Because there are both the split systems and one package system for the DX units the parts are going to be different. The packaged systems contain all four pieces of the RVEC system (evaporator, condenser, compressor, expansion device along with some unit controls). This includes internal ducting and fans. The split systems contain fans and the evaporator within the building. The rest of the RVEC system components are placed outside of the building as separate units allowing greater flexibility.
A. The purpose of each component.
The system will boast a hot water heating coil, a DX cooling coil, as well as an integral energy wheel. The cooling capacity is at thirty tons and utilizes CO2 sensors plus a VFD to change the quantity of Exhaust Air as well as Outside Air, based on existing occupancy of the building. The ductwork which covers return, supply, exhaust, and outside air will be galvanized sheet metal will have external duct insulation as its main insulation. Along with each VAV terminal unit will be sound attenuators. The three HVAC systems are the following: one DX packaged unit (at east end of building, outside) and two DX split systems. Ventilation is important and the Mechanical Room will include ventilation (exhaust with 200 CFM capacity) and heat (1KW wall heater).
B. How the component works.
The heating and cooling coils warm and cool the air and the energy wheel transfers back the heat. VAV or Variable Air Volume can serve various purposes and can act as a heating, air conditioning, and/or ventilating system with a constant supply of airflow at variable temperatures. Sound attentuators act like duct silencers for HVAC systems. The galvanized sheet metal ducts offer easy fitting and flexibility so the flow of air is unencumbered.
C. How the components work together.
The air needed to cool down the spaces is directly chilled by the systems' refrigerant located in the cooling coil. Since the refrigerant directly cools the air (the same for heating coil) there is higher cooling efficiency. Refrigerant piping however, cannot always e carried large distances. That is why there is one unit in the first floor, one in the basement, and an external part applied to the east of the building.
(2) Discuss the controls of the system and who installs the controls.
The controls are part of the APR Control which is a capacity-control device modulating refrigeration/air conditioning capacity that matches fluctuations happening within the BTU quantity of an existing load. The unit reads the heat content the returning air within the system and then changes the pressure of the suction gas. The APR Control can sense variations via the evaporator coil and the enthalpy of retuning air. The kind of person that installs an APR Control is a refrigeration mechanic and takes around 4-6 hours.
(3) Discuss the process of the cooling cycle through the system.
Air passes over an indoor cooling coil, heating cold liquid refrigerant, transforming it into a warm gas/vapor. A copper tube then transfers the vapor to the compressor, compressing it and increasing pressure. The hotter vapor goes through another heat exchanger, which is called an outdoor condenser. The hot gas then transforms into a warm high pressure liquid. It goes through a liquid line or a smaller copper tube and then to a dryer/filter, before making its way to an expansion device, minimizing the high pressure liquid to a low pressure and cold liquid. Then finally, the cold liquid goes through an indoor cooling coil, repeating the cycle.
(4) Discuss the process of the heating cycle through the system.
The same process exists within the heating cycle as it does the cooling cycle with one exception. The heating cycle incorporates a special valve located in the refrigeration piping reversing the refrigeration cycle. In colder weather, a defrost period is necessary for a heat pump.
(5) Discuss the energy conservation measures, if any, for the building.
The DX systems offers flexibility and lower costs as well as lower maintenance. The packaged and split systems can be used for a variety of situations with high capacity. The lower costs come from lower maintenance which leads to energy conservation. Sealing and insulating the ductwork also saves energy and reduces leaks.
(6) Why was this system used as compared to another?
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