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:
And in Article " Electrical Wiring Diagrams for Air Conditioning Systems – Part One ", I explained the following points:
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:
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.
7.2 Overview of a Water Chiller
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.
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.
The part of a chiller system where the refrigerant vapour is converted to liquid as it rejects heat.
A device used to supply uniform gas supply through a submerged coil in a tank chiller 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.
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
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)
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
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.
The model drawing and main components are indicated as in Fig.6.
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:
Also, the Legend, Notes & wiring diagram for optional items used for this model is indicated in Fig.8.
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)
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:
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.