Electrical Wiring Diagrams for Air Conditioning Systems – Part Three

In Article " Electrical Rules and Calculations for Air-Conditioning Systems – Part One ", which was the first Article in our new Course HVAC-2: Electrical Rules and Calculations for Air-Conditioning Systems, I explained the following points:

• Introduction for Air-Conditioning Systems Types,
• Introduction for Types of Motors/Compressors used in Air-Conditioning Systems.

And in Article " Electrical Wiring Diagrams for Air Conditioning Systems – Part One ", I explained the following points:

• Importance of Electrical Wiring for Air Conditioning Systems,
• How to get the Electrical Wiring for Air Conditioning systems?,
• Types of Electrical Wiring Diagrams For Air Conditioning Systems,
• How to read Electrical Wiring Diagrams?

Third: Electrical Wiring Diagrams for Air-Conditioning Systems - Continued

The Electrical wiring diagrams for Typical Air conditioning equipment The main types and equipments in common Air conditioning systems were: Window air conditioning units, Split air conditioning units, Multi-Split air conditioning units, Mini-heat pumps, Split Packaged units, Unitary Packaged units, Chillers, Air Handling Units, Fan Coil Units, Pumps, VAV boxes, Dampers.

In Article " Electrical Wiring Diagrams for Air Conditioning Systems – Part Two ", I explained the electrical wiring diagrams for some Typical Air conditioning equipments.


Today, I will explain Electrical Wiring Diagrams for other Typical Air-Conditioning Equipment.

7- Chillers

7.1 Overview of Central HVAC Systems A heating, ventilating and air-conditioning (HVAC) system is a simple system of heating and cooling exchangers using water or refrigerant (direct expansion system) as the medium. Pumps move the heated or cooled water to the exchangers. Fans then move the warmed or cooled air created at the exchangers to the occupied building interiors. So there are two stages to heating and cooling which are: Water stage: water is the most efficient and inexpensive medium that we can cool directly (through a chiller) or heat (through a boiler) Air stage: air is the medium for heat exchange in the building as it can be cooled or heated through coils. Fig.1 below illustrates a typical HVAC system showing water and air heat exchangers with the main components of the system which are: Fig.1: Typical HVAC Central System Fans: for air circulation and ventilation. Chillers: for the production of chilled water for large buildings (note: for small buildings use the direct expansion cooling systems such as packaged air-conditioners). Boilers: for the production of hot water for Heating (note: it is often to use the electric heaters for zonal reheat). Pumps: for the circulation of heating hot water, chilled water and condenser water. Cooling towers: for heat rejection. The primary energy use is the cooling tower fan and pumps. Controls: coordinate the operation of the mechanical components together as a system.

7.2 Overview of a Water Chiller A chiller is a mechanical refrigeration device, like an air conditioner, except that it cools a fluid (usually water) instead of cooling air. When a large air conditioner is required it is sometimes more feasible to use one large chiller instead of many small air conditioners. Chillers are also used wherever there is a need for cooling a fluid such as a chemical process or for plastics molding. To simplify the concept of a chiller you should compare it to a drinking fountain where you get cold “chilled” water. There are a variety of water chiller types (see Fig.2). Most commonly, they are absorption, centrifugal, helical rotary, and scroll. Some reciprocating chillers are also available. Fig.2: Types of Chillers For more information about Chillers and their types, please review Article " HVAC Systems Main Equipment ".

  

7.3 The Major Components of a Water Chiller A chiller consists of a few major components as follows: 1- The condenser heat exchanger: It can be either air-cooled, a coil or coils and a fan or fans, or water-cooled, another shell & tube heat exchanger cooled by cooling tower or other water. 1.1 Air cooled condenser: A type of condenser where refrigerant flows through the tubes and rejects heat into a flow of ambient air, most chiller units are fitted with air cooled condensers. 1.2 Water Cooled Condenser: A type of chiller condenser that uses water to remove heat from the refrigerant, this is normally a shell & tube type design. 2- Capillary Tube: A type of expansion device typically fitted on small capacity hire chillers, it comprises a long tube which reduces the pressure of the refrigerant. Centrifugal Fan – A type of fan fitted to an air cooled chiller allowing the fitting of ductwork onto the hot side of an air cooled condenser. The fan is designed to work against a static pressure. 3- Compressor: The main component in a chiller system, the compressor is used to increase the pressure & temperature of the refrigerant vapour. Compressors are usually reciprocating, scroll, centrifugal, or rotary screw types. 4- Condenser: The part of a chiller system where the refrigerant vapour is converted to liquid as it rejects heat. 5- Distributor: A device used to supply uniform gas supply through a submerged coil in a tank chiller evaporator. 6- Evaporator: The part of the chiller system where cool liquid refrigerant absorbs heat from the chilled water circuit. It is usually of shell & tube constructions and is the exchanger where chilled water would be produced. 6.1 Shell & Tube Evaporator: A type of evaporator where refrigerant flows through the tubes & chilled water fills the surrounding shell 7- Expansion valve: A device used to maintain the pressure difference between the high pressure & low pressure sides of the chiller system. 8- Hot Gas Muffler: A device installed at the discharge side of the chiller compressor to reduce noise and vibration in reciprocating compressors. 9- Liquid Line Filter Drier: A device installed in the liquid line to remove moisture and foreign matter, designed to protect the chillers compressor. 10- Shut Off Valve: It is used to isolate one part of the chiller system from the rest. 11- Sub-Cooler: It is the lower portion of the chillers condenser that further cools the saturated liquid refrigerant. 12- Suction Header:  A section of pipe within the chiller system used to collect the refrigerant vapour when it leaves the tubes of a submerged coil evaporator 13- Suction Line Filter: A devise installed into the chillers suction line to remove foreign matter from the refrigeration system 14- Cabinet: Cabinet is made from heavy gauge galvanized steel. Steel sheet panels are zinc coated and galvanized by hot dip process followed by air dry paint or backed on electrostatic polyester dry powder coat. 15- Control Panel: (see Fig.3) Fig.3: Example of Chiller Control Panel The control panel design is equivalent to NEMA 4 (IP55) with hinged door for easy access ensuring dust and weatherproof construction. Internal power and control wiring is neatly routed, adequately anchored and all wires identified with cable markers as per standards applicable to HVAC industry. The electrical controls, used in the control panel, must be reliable in operation at high ambient conditions for a long period.

7.4 The Electrical Wiring Diagrams for a Water Chiller Fig.4: Air cooled screw water chillers    Let’s take an example for Water Chillers like Air cooled screw water chillers from Cooline Co. model # ASQ115B, the following electrical data for this model will be as in Fig.5. Fig.5: Electrical Data for Cooline Co. model # ASQ115B The model drawing and main components are indicated as in Fig.6. Fig.6: Cooline Co. model # ASQ115B- Drawing and Main Components     And a Typical Schematic Wiring Diagram (Part Winding Start) for this model is indicated in Fig.7. Fig.7: Cooline Co. model # ASQ115B -Typical Schematic Wiring Diagram you can note that Fig.7, Fig.6 and Fig.5 must be identical for: the number of compressors = 2. the number of condenser fans = 8. Also, the Legend, Notes & wiring diagram for optional items used for this model is indicated in Fig.8. Fig.8: Cooline Co. model # ASQ115B- Legend, Notes & wiring diagram

7.5 The Field Wiring For Chillers Internal power and control wiring is neatly routed, adequately anchored in manufactures' factory prior to delivery. The connections that must be made by the installer are as follows: A- Connection to the power network: (see Fig.9) Fig.9: Chillers Connection to the power network Field power wiring is a single point connection; Main 3 phase power must be supplied from a single field supplied and mounted Disconnect switch, using dual element time delay fuse or circuit breaker with Rating as recommended by manufacturer. Also, electrical lugs for incoming power are provided by manufacturer. B- Connection to the control and monitoring system: Interlocking connections are needed with water flow switch, pumps, remote monitoring system and two barrel units water temperature sensor, if any.

8- Air Handling Units, Fans, and Pumps

8.1 The Field Electrical Wiring for other Major Components in Central HVAC System Field power wiring for other Major Components in Central HVAC System like Pumps, Fans and AHUs are also a single point connection as in the case of Chillers but we must use some type of motor starters or/and Variable frequency drives (VFDs) as follows: If you will use DOL starters (see Fig.10), you must install a separate Disconnect switch, using dual element time delay fuse or circuit breaker (see Fig.11) with Rating as recommended by manufacturer. Fig.10: Examples for DOL Starters Fig.11: The Field Electrical Wiring for Loads with DOL Starters and VFD And if you use VFD which you must install a separate Disconnect switch, using dual element time delay fuse or circuit breaker (see Fig.11) with Rating as recommended by manufacturer. But if you use DOL combination starters (see Fig.12) which come with a Disconnect switch or circuit breaker built in the unit (see Fig.13). This will eliminate the cost of wiring between separate disconnect means and starters. Fig.12: Examples for DOL Combination Starters Fig.13: The Field Electrical Wiring for Loads with DOL Combination Starters

In the next Article, I will explain in detail Different Types, Locations and Sizes of Disconnecting Means used for HVAC Systems. So, please keep following.

 

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Electrical Wiring Diagrams for Air Conditioning Systems – Part Two

In Article " Electrical Rules and Calculations for Air-Conditioning Systems – Part One ", which was the first Article in our new Course HVAC-2: Electrical Rules and Calculations for Air-Conditioning Systems, I explained the following points:

• Introduction for Air-Conditioning Systems Types,
• Introduction for Types of Motors/Compressors used in Air-Conditioning Systems.

And in Article " Electrical Wiring Diagrams for Air Conditioning Systems – Part One ", I explained the following points:

• Importance of Electrical Wiring for Air Conditioning Systems,
• How to get the Electrical Wiring for Air Conditioning systems?,
• Types of Electrical Wiring Diagrams For Air Conditioning Systems,
• How to read Electrical Wiring Diagrams?

Today, I will explain Electrical Wiring for different Air-Conditioning Systems Types and Equipment.

Third: Electrical Wiring Diagrams for Air-Conditioning Systems - Continued

The Electrical wiring diagrams for Typical Air conditioning equipment The main types and equipments in common Air conditioning systems were: Window air conditioning units, Split air conditioning units, Multi-Split air conditioning units, Mini-heat pumps, Split Packaged units, Unitary Packaged units, Chillers, Air Handling Units, Fan Coil Units, Pumps, VAV boxes, Dampers.

1- Window Air Conditioning Units

1.1 Window Air Conditioning Units Construction Window air conditioning unit casing houses the following components: (see Fig.1) Fig.1: Window Air Conditioning Units Construction Condenser (outdoor coil), Condenser fan, Hermetic compressor, Evaporator (indoor conditioning coil), Evaporator fan (blower), Controls: The controls for window units are simple and inbuilt, it includes: (see Fig.2) Fig.2: Window Air Conditioning Units Controls A rotating selector/Mode switch marked with a hot-cold scale of five positions (off, high cool, low cool, high fan, low fan) with no temperature settings. A rotating Thermostat switch work as on/off switch for the compressor, its status is depending on what temperature/cooling degree you set it at (usually there are 8  positions for cooling degree). Louvers swing switch: it is on/off switch which controls the swing motor responsible for controlling the movement and direction angle in which the air be supplied from the louvers to the room.

1.2 The power flow in Branch circuit of a Typical Window air conditioning unit The Window air conditioning units are fed from single phase power source (see Fig.3), so its branch circuit and its main power cord consisting of 3 wires (The ground wire, hot wire and neutral wire). Fig.3: Window Air Conditioning Unit Power Circuit The branch circuit will originate from one of the single pole Overcurrent protective device OCPD included in an electrical panel. Then go through raceway system (conduits, ducts, …) to a disconnect means of some type suitable for the application . Finally, the main power cord of the Window air conditioning unit is connected to this disconnecting means from one side, the other side enters the casing of the unit to be connected to the unit’s terminal box.

1.3 Electrical wiring connections inside The Window air conditioning units Here we are interested on how the main power cord is connected inside the unit and this can be explained as follow (see Fig.4): Fig.4: Window Air Conditioning Unit Internal Electrical Wiring A- Inside the unit the main power cord is split to: The ground wire (either green or a bare wire) is screwed to the metal casing of the unit. Hot wire Neutral wire. B- Hot wire goes to the selector switch on a window unit to feed power to the vital parts, compressor and fan motor as follows: Hot wire to selector switch to thermostat switch to compressor Hot wire to selector switch to fan motor. C- Neutral wire will be connected to fan motor and compressor without goes through any switch. These connections are made on the wire connector in the back of the selector switch so, all neutral wires are common to each other because they are connected to the same point. some examples for the complete electrical wiring diagrams for Window Air Conditioning Unit are in Fig.5. Fig.5: Window Air Conditioning Unit Electrical Wiring Diagrams Also, in Fig.6, you can find examples for the complete wiring diagrams for Window Air Conditioning Unit which be mounted on the unit casing. Fig.6: Window Air Conditioning Unit Electrical Wiring Diagrams - Factory built-in also, you can find examples for the complete wiring diagrams for Window Air Conditioning Unit, touch and remote control type in Fig.7. Fig.7: Window Air Conditioning Unit Electrical Wiring Diagrams - Touch and Remote Control Type

1.4 The power flow inside a Typical Window air conditioning unit in the cooling mode When you turn the selector switch to cool mode, the power that came in from the cord that connected to the selector via hot wire goes to the fan so the fan operates. The selector switch also sends the power via hot wire to the compressor, but the compressor will not operate until the thermostat comes to the on position, then the compressor will operates and the cooling cycle begin.

2- Split Air Cooling Units

2.1 Split air Cooling Units Construction The split systems are individual systems in which the two heat exchangers are separated (one outside, one inside) (see Fig.8). There are two main parts of the split air conditioner which are: Fig.8: Split air Cooling Units Construction Outdoor unit, Indoor unit. 1- Outdoor unit: This unit is installed outside the room or office space which is to be cooled and houses important components of the air conditioner like: The compressor, Condenser Cooling Fan, Expansion Valve. 2- Indoor unit: The most common type of the indoor unit is the wall mounted type though other types like ceiling mounted and floor mounted are also used. The indoor unit produces the cooling effect inside the room or the office and houses the following components: The evaporator coil or the cooling coil, Cooling Fan or Blower, The drain pipe, Louvers or Fins, Air filter, Controls.

2.2 The power flow in Branch circuit of a Typical split air conditioning unit The split air conditioning units are fed from either: Single phase power source (see Fig.9 and Fig.11), so its branch circuit and its main power cord consisting of 3 wires (The ground wire, hot wire and neutral wire). Or Three phase power source (see Fig.12), so its branch circuit and its main power cord consisting of 5 wires (The ground wire, 3 hot wires and neutral wire). Fig.9: Split air Cooling Units - Single Phase - Indoor feed Outdoor  Fig.10: Split air Cooling Units - Single Phase - Electrical Wiring Diagram Fig.11: Split air Cooling Units - Single Phase - Outdoor feed Indoor Fig.12: Split air Cooling Units - Three Phase  Fig.13: Split air Cooling Units - Three Phase - Electrical Wiring Diagram The branch circuit will originate from one of the single pole/three pole Overcurrent protective device OCPD included in an electrical panel. Then go through raceway system (conduits, ducts, …) to a disconnect means of some type suitable for the application. After that, the main power cord of the split air conditioning unit is connected to this disconnecting means from one side, the other side is connected to the terminal box in the indoor unit (see Fig.9) or in the outdoor unit (see Fig.10)according to the manufacturer’s recommendations and wiring diagrams. Note: if power source connections made in indoor unit, an indoor disconnecting means is used and if power source connections made in outdoor unit, an outdoor disconnecting means (see Fig.14) with suitable identity of protection (IP) is used (review the manufacturer’s recommendations and wiring diagrams). Fig.14: Outdoor Disconnecting Means Finally, the power is transferred via 3-wire cable or 5-wire cable from the terminal box in indoor unit to the terminal box in outdoor unit or vice versa as indicated in the above point. Note: There is a signal cable also connecting the control in the indoor unit with the control in the outdoor unit.

2.3 Electrical wiring connections inside The Split air conditioning units The electrical wiring inside both of indoor and outdoor units is more complicated than that of window air conditioning units. It is always factory wiring and from our point of view as electrical power engineers, it will not affect our work at all. However, we provide some examples for the electrical wiring diagrams including control wiring for reference as in below Fig.15.   Fig.15: Split air conditioning units - Internal Electrical wiring Diagram

3- Multi-Split Air Conditioners

3.1 The power wiring for multi-split air conditioners These days, Multi-split air conditioners are also being used commonly (see Fig.16). In units for one outdoor unit there are two indoor units which can be placed in two different rooms or at two different locations inside a large room. Fig.16: Multi-split air conditioners The power wiring for multi-split air conditioners will be as in Fig.17 below.    Fig.17: Multi-split air conditioners Power Wiring in Fig.18, you can find examples for the complete wiring diagrams for Multi-split air conditioners. Fig.18: Multi-split air conditioners Electrical Wiring Diagram

4- Mini- Heat Pumps

4.1 The power wiring of Mini- Heat Pumps   The power wiring of Mini- Heat Pumps will look like that of the Split air Cooling Units for far extent (see Fig.19).  Fig.19: Mini-Heat Pumps However, you can find in below some examples for wiring diagrams for Mini- Heat Pumps (see Fig.20) and you can compare them with that of Split air Cooling Units especially in the power (high voltage) wiring. Fig.20: Mini-Heat Pumps Electrical Wiring Diagram

5- Split Packaged Units

5.1 Split Packaged Units Construction A split system describes an air conditioning or heat pump system that is split into two sections (see Fig.21)which are: Outdoor section, Indoor section. Fig.21: Split Packaged Units Construction 1- Outdoor section: The outdoor unit is located outside usually on the ground but sometimes on the roof. It houses the following components: Compressor(s), Condenser coil(s), Condenser fan(s), Condenser's fan motor(s), Fan grille, Shut off valves, Reversing valve, Optional accessories (if any). 2- Indoor section: The indoor section usually located in an interior closet or garage. It houses the following components: Blower(s), Evaporator coil, Thermal expansion valve(s) and distributor(s), Bearings and shaft, Optional accessories.

5.2 The Electrical wiring in Split Packaged units The Electrical wiring in Split Packaged units consists of 3 main parts as follows: High voltage part (power part), High voltage control and motors part, Low voltage control part. 1- High voltage part (power part):(see Fig.22) Fig.22: Electrical wiring of Split Packaged unit - High voltage part The branch circuit will originate from one of the three pole Overcurrent protective device OCPD included in an electrical panel. Then go through raceway system (conduits, ducts, …) to : A disconnect means of indoor unit (Air handler unit), A disconnect means of outdoor unit (condenser/evaporator unit). 2- High voltage control and motors part:(see Fig.23) Fig.23: Electrical wiring of Split Packaged unit - High voltage control and motors part This includes the high voltage wiring inside air handler unit and inside condenser/evaporator unit. Inside the air handler unit, the high voltage wiring powers the indoor fan, the heater and provide power for the transformer. Inside the condenser/evaporator unit, the high voltage wiring powers the outside fan and the compressor. 3- Low voltage control part: This part has (2) mode for operation which are: A/C Mode, Heat Mode. A- In the A/C Mode:(see Fig.24) Fig.24: Electrical wiring of Split Packaged unit - Low voltage control part - A/C Mode The thermostat send signal in (2) directions as follows: Via the Y wire to turn on the outside fan and the compressor, Via the G wire to turn on the indoor fan. B- In the heat Mode:(see Fig.25) Fig.25: Electrical wiring of Split Packaged unit - Low voltage control part - heat Mode Also, the thermostat, in this mode, sends signal in (2) directions as follows: Via the G wire to turn on the indoor fan, Via the W wire to turn on the heater. So, the complete wiring diagram will be as in Fig.26 below: Fig.26: Electrical wiring of Split Packaged unit - Complete Circuit Note: The thermostat usually have (5) positions which are Off – Cold – Auto – Heat – on. You can find in below some examples for wiring diagrams for split packaged units with different starting methods in Fig.27.   Fig.27: Electrical wiring of Split Packaged unit with different Starting Methods

6- Unitary Packaged Units

6.1 The power circuit for Unitary packaged units Unitary packaged systems (see Fig.28) are by far the most commonly used air conditioning equipment in commercial buildings. A packaged air conditioning unit is a self-contained air conditioner. It provides the cooling, heating and the motion of the air. All the components needed for cooling, heating, and air movement are assembled in a steel casing.  Most packaged units use semi hermetic compressors which mean that the motor and compressor unit are mounted in one housing. Fig.28: Rooftop packaged units Construction Unitary Packaged units are packaged units which come as one single package that is ready to be mounted on a rooftop or on ground floor for some types. Rooftop packaged units can be classified according to the type of heating they supply. There are rooftop packed units with either electric heating or gas-fired heating. The heating can also be provided by a heat pump. However, electric heat and gas-fired furnaces are mainly used. The available cooling capacity of common packaged rooftop units ranges from 10 kW (3 tons) to 850 kW (241 tons). The air flow rate covers a range from 400 l/s (850 ft3/min) to 37,800 l/s (80,000 ft3/min). The power Schematic diagram for Rooftop packaged units is shown in Fig.29. Fig.29: Power Schematic diagram for Rooftop packaged units

In the next Article, I will explain Electrical Wiring Diagrams for other Air-Conditioning Systems Equipment. So, please keep following.

 

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