| Overview

The Central Plant is a combination of more than a few equips that contribute to the whole cooling process.

The equips that contribute to a chiller plant vary with the plant.

The equips can be categorized into primary and secondary equips.

Primary Equips 

  • Chiller
  • Cooling Tower
  • Pumps
  • Valves
  • Boilers
  • Heat Exchanger

Secondary Equips

  • Pipes
  • Temperature Sensors
  • Well Sensors
  • Energy Meters
  • Flow Meters
  • Flow Switch

| Chillers

Chillers in the chiller plant are the major contributor to the cooling process. The chiller is a combination of an evaporator, condenser, compressor, and Expansion valve.

The chillers can be of two types.

  • Water Cooled Chiller 
  • Air Cooled Chiller

Water Cooled Chiller


In a water-cooled chiller the condenser water, which is sealed, is pumped into a cooling tower, and the heat is removed in the cooling tower.


In an air-cooled chiller, a series of fans run over an exposed condenser water pipe, and the heat is removed from the condenser water.

| Cooling Towers

A cooling tower is used in a chiller plant that uses a water-cooled chiller.

The cooling towers can be of 3 types, based on the number of fans used.

1 Fan Cooling Tower


As the name suggests the 1-Fan cooling tower, uses a single fan, with a single water input and output.

2 Fan Cooling Tower


The 2-Fan cooling tower uses two fans with two water inputs and outputs.

4 Fan Cooling Tower



The 4-Fan cooling tower uses 4 fans with 4 water inputs and outputs.

| Pumps

Pumps are used to push the water from the evaporator to the building load as in the Air Handling Units, and from the condenser to the cooling towers in the case of a water-cooled chiller.


The pumps can be of two types based on usage.

Dedicated Pumps

When a pump serves just one chiller it is called a dedicated pump.

Headered Pumps

When a pump serves more than just one chiller it is called a headered pump.

The pumps can also be classified based on the side of the chiller plant it supports. 

Condensed Water Pump

When the pump supports the condenser side of the chiller plant it is called the Condensed Water Pump pump.

Chilled Water Pump

When the pump supports the chilled water side of the chiller plant it is called the Chilled Water Pump

The pumps can also be classified based on the circuit of the chiller plant it supports. 

Primary & Secondary Circuit Pumps


| Valves and Valve Actuator


The valve and valve actuator are used to open/close or regulate the amount of water passing through the water pipe.

| Water Pipes


The water pipes. connect the chiller, and pumps to the building load and cooling towers.

| Temperature Sensor


A Temperature Sensor, as the name suggests, senses the temperature i.e., it measures the changes in the temperature. The temperature sensor is installed in the water pipe and measures the temperature of the running or stagnant water in the pipe.

| Thermowell

It measures the temperature of water by inserting a well in the water pipe. Over this thermowell, the temp sensor is mounted.

| Flow Sensor/Meter


A flow sensor (more commonly referred to as a “flow meter”) is an electronic device that measures the flow rate of liquids within pipes and tubes. 

Flow sensors are able to detect leaks, blockages, pipe bursts, and changes in liquid concentration due to contamination or pollution.


Flow sensors can be categorized into two types.

Contact Flow Sensors

Contact flow sensors are used in applications where the liquid or gas measured is not expected to become clogged in the pipe when it comes into contact with the sensor’s moving parts.

Non-Contact Flow Sensors

In contrast, non-contact flow sensors have no moving parts, and they are generally used when the liquid or gas (generally a food product) being monitored would be otherwise contaminated or physically altered by coming into contact with moving parts.

| Differential Pressure Sensor


Differential pressure refers to the pressure between two places. Different industries use differential pressure sensors to measure this unique type of pressure. 

There are three common types of pressure exist: 

Differential Pressure sensors have two ports connected to the two different pressure sources. It follows the pressure between the two places. If the pressure reaches a particular point, then the internal diaphragm in the switch will make contact after deflecting. This contact will either make or break a circuit. The change in the circuit will trigger an alarm that tells the user that the pressure has changed. 

| Flow Switch


A flow switch is a device that monitors the flow of liquid i.e. water in the water pipes in the chiller plant. It sends a "signal" to a BMS controller in the system and can tell the status if the pump is shut off or turned on. 

| BTU Meter



BTU meters measure the energy content of liquid flow in British thermal units (BTU), a basic measure of thermal energy. BTU meters are used in chilled water systems for both commercial and industrial and office buildings. These meters are used to bill users for energy usage.

The BTU meter automatically integrates energy consumption and transfers it to the system with which the consumption volume can be tracked It provides real-time information such as instantaneous temperature, flow rate, energy consumption, and others.

| 75F CPM Equipment Definitions

To avoid confusion and ease the chiller plant schematic building, the equipment for the 75F CPM is defined in a particular way. This way of defining the equipment would provide the user with a better understanding of what sub/secondary equipment connects to the main/primary equipment, and help in building the schematic with great ease.

This also helps the user to better differentiate between the smaller, similar looking equips like pipes, sensors, meters, and pumps.

Below is a table that talks about the equipment definition in the 75F CPM.

Equip Sub Equip Color Scheme
Water Cooled Chiller  Chilled Water Entering Pipe Equip  Blue
Chilled Water Leaving Pipe Equip  Orange
Condenser Water Entering Pipe Equip  Orange
Condenser Water Leaving Pipe Equip  Blue
Air Cooled Chiller  Chilled Water Entering Pipe Equip   
Chilled Water Leaving Pipe Equip  
Cooling Tower  Condenser Water Entering Pipe Equip   
Condenser Water Leaving Pipe Equip   
Building Block/Cooling Load Chilled Water Entering Pipe Equip   
Chilled Water Leaving Pipe Equip   
Building Block/Heating Load

Hot Water Entering Pipe Equip   
Hot Water Leaving Pipe Equip   
Condenser Water Pump NA NA
Chilled Water Pump  NA NA
Secondary Chilled Water Pump  NA NA
Tertiary Chilled Water Pumps 2 Nos NA NA
Condenser Water Return Header Pipe NA Orange
Condenser Water Supply Header Pipe NA Orange
Chilled Water Supply Header Pipe NA Blue
Chilled Water Return Header Pipe NA Blue
Hot Water Return Header Pipe NA Orange
Hot Water Supply Header Pipe NA Orange
BTU Meter at the building side NA NA
Hot Water BTU Meter at the Building Side NA NA
Gas Boiler NA NA
Decoupler Line/Bypass Pipe  NA NA


When the equipment is defined as shown in the above table, building the schematic for the chiller plant is so easy, that when a piece of primary equipment is dragged into the canvas the sub-equips related to the primary equipment also come with it. for more information on the building the chiller plant schematic refer to Setting Up the Central Plant Schematic.





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