Electrical Rules and Calculations for Air-Conditioning Systems – Part One

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 First: Introduction for Air-Conditioning Systems Types

 1- Air-Conditioning Systems TypesAs we explained before in our course HVAC-1: An introduction to heating, ventilation and air conditioning (HVAC) systems that the HVAC system can be divided to (2) main systems:Heating systems,Cooling systems.Here, we are interested in the cooling systems or what we will called “ Air Conditioning systems” in this course, which in turn divided to (4) sub-main systems:De-centralized systems (individual room systems),Semi-centralized systems (packaged systems),Centralized systems (central Hydronic systems),Special systems.
 1.1 De-Centralized Systems (Individual Room Systems)These systems include:Window air conditioning units,Split air conditioning units,Mini-heat pumps.Window air conditioning unitsSplit air conditioning unitsMini-heat pumps
 1.2 Semi-Centralized Systems (Packaged Systems)These systems include:A- Unitary packaged systems (one pipe systems) which can be divided to:Packaged air conditioners with water cooled condensers,Packaged air conditioners with air cooled condensers.Packaged air conditioners with water cooled condensers -1Packaged air conditioners with water cooled condensers -2Roof Top Packaged air conditioners with air cooled condensersB- Ducted split systems (two pipes systems)Ducted split systemsAlso, the units used in packaged systems can be divided to:Rooftop packaged units,Indoor packaged units,Split units,A- Roof Top Packaged Units:Roof top packaged units (RPU) are an all in one air cooled A/C unit that are installed on top of the roof and can provide cooling and heating. The condensing unit and the air handler reside inside a single housing. In order to connect the unit to the inside duct work, an opening on the roof for supply and return air is necessary. The duct work distributes the air evenly through-out the space. Heating can be provided by reversing the condensing unit (heat pump) or connecting an electric heater, gas heater, or steam coil.Roof Top Packaged UnitsB- Indoor Packaged Units:Indoor package units (IPU) are similar to rooftop units, but because the unit is located inside, it requires a different way of cooling the condensing unit. The most common way, is air-cooled using louvered openings (horizontal angled slats that prevent outside weather to come inside, but allow air flow) to get fresh outside air. In situations where there is no access to fresh outside air, water cooled units are the best solution. Indoor units come in vertical, or space saving horizontal configurations. These units are the same as roof top units in the way they connect to duct work and have the same heating options as mention in the roof top packaged units.Indoor Packaged UnitsC- Split Packaged Systems:Split systems are comprised of a condensing unit (a condensing coil and a compressor) located outside, and an air handler (pushes air across the evaporator coil) located inside. Refrigerant lines for high and low pressure are run from the condensing unit to the air handler. Since the high pressure lines get cold, they are covered with insulation to prevent condensation issues and having water accumulate inside the space. The air handler comes in different configurations to best fit the desired installation. Split Systems can be divided to:Ducted (Connected to duct work),Ductless (wall mounted, ceiling suspended, ceiling cassettes, and floor standing).You may also have multiple air handlers connected to one condensing unit in computer controlled split systems. Ducted Split Packaged SystemsDuctless Split Packaged Systems
 1.3 Centralized Systems (Central Hydronic Systems)These systems include:Centralized duct “All air” systems,Centralized fluid based hydronic systems “all water systems”,Combined (hybrid) water and air systems.Centralized duct “All air” systems ConceptCentralized “all water systems” ConceptCombined (hybrid) water and air systems Concept

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