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CRAC Controls- A Guide

Computer Room Air Conditioning: Chapter 3


CRAC System Controls


In this module, we will learn about the controls in computer room air conditioning systems (CRACs).Skip to quiz!


Controls


Recall that HVAC control systems are used to control the operations of HVAC equipment. Control systems use a small amount of control voltage to control larger voltage-connected equipment. Remember that control voltages are usually 24 volts DC.


Some of the sensors that we find in CRAC systems are:

  • Temperature sensors,

  • Humidity sensors,

  • Pressure sensors,

  • Smoke sensors,

  • Contact sensors, and

  • Water sensors.

We’ll learn about these sensors in detail.


Most CRAC systems have an electronic control board that receives signals from these sensors and controls different components. Temperature sensors are installed in CRAC systems to detect the temperature of air.


Temperature sensors send control signals to a system to control the flow of water or refrigerant in cooling coils. They can also control the speed of blowers in a CRAC system.


We install humidity sensors in CRAC systems to detect the moisture content of air. They send signals to a CRAC system to control humidity. They also control the operation of humidifiers or dehumidifiers if a CRAC has them.


We install pressure sensors in CRAC systems to detect the pressure of air. Blower speed increases or decreases depending on the input given by a pressure sensor. They tell us if air filters are dirty or clean. Recall that dirty air filters will not allow air to pass through them easily.


Smoke sensors detect smoke as a primary indication of fire. They provide a signal to the fire alarm system or produce an audible and visual alarm. Properly installed and maintained smoke sensors play a vital role in reducing fire accidents.


Contact sensors are also known as position sensors or status sensors. They tell whether a door or window is open or closed.


These sensors come in two pieces:

  • One is fixed to a door or window, or

  • Another is fixed to its frame.


Water sensors are installed under racks to detect water leaks. These detect the presence of water where water should not be present, a leak. These provide an alert in case of water leakage so that we can act quickly to prevent further damage.


HVAC control systems are used to control the operations of HVAC equipment.


Some of the sensors that we find in CRAC systems are:

  • Temperature sensors,

  • Humidity sensors,

  • Pressure sensors,

  • Smoke sensors,

  • Contact sensors, and

  • Water sensors.


 

Question #1: Which of the following sensors in the CRAC systems is used to detect the moisture content of air?

  1. Pressure sensors

  2. Humidity sensors

  3. Contact sensors

  4. Smoke sensors

Scroll down for the answer...









Answer: Humidity sensors

Humidity sensors are installed in the CRAC systems to detect the moisture content of air.


Question #2: Which of the following sensors play a vital role in reducing accidents?

  1. Humidity sensors

  2. Pressure sensors

  3. Contact sensors

  4. Smoke sensors

Scroll down for the answer...















Answer: Smoke sensors

Properly installed and maintained smoke sensors play a vital role in reducing fire accidents.


Question #3: Contact sensors come in ____ pieces.

  1. Two

  2. Three

  3. Four

  4. Six

Scroll down for the answer...















Answer: Two

Contact sensors come in two pieces.

  • One is fixed to door or window

  • Another is fixed to its frame


Question #4: Which of the following sensors are installed under server racks to prevent a short circuit due to water?

  1. Humidity sensors

  2. Pressure sensors

  3. Water sensors

  4. Smoke sensors

Scroll down for the answer...

















Answer: Water sensors

Water sensors detect the presence of water where water should not be present. They are installed under server racks to prevent a short circuit due to water.



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