The computing power industry is developing rapidly, and the data center carries the core business and data storage work of the enterprise.Precision IT equipment such as servers, GPUs, switches, etc. are extremely sensitive to temperature and humidity. Small environmental fluctuations can easily cause static electricity, corrosion, downtime, data loss and other failures, which seriously affect the stable operation of the computer room.
Computer room precision air conditioning (CRAC) is specially designed for the harsh working conditions of computer rooms. It is different from ordinary comfortable air conditioners. It relies on the advantages of high-precision, all-weather, and intelligent control to ensure the stable operation of IT equipment.This article comprehensively explains the computer room temperature and humidity control standards, CRAC core control technology, hardware configuration, operation and maintenance difficulties and industry trends, and provides a reference for data center equipment selection and operation and maintenance optimization.
Understanding Temperature and Humidity Requirements in Computer Rooms
There is an essential difference between the environmental control of the computer room and ordinary office and residential spaces. The core positioning and implementation standards are completely different. The specific classification is as follows：
Differences in regulation requirements: Ordinary commercial and household air conditioners aim at the comfort of the human body, with loose regulation scope and high fault tolerance.The CRAC computer room precision air conditioning is specially designed for IT equipment working conditions. The core goal is to ensure the stable operation of the equipment, extend the service life of the hardware, and avoid operation and maintenance risks such as static electricity, corrosion, and downtime. Environmental stability, accuracy, and continuity requirements are extremely high.
Industry implementation standards: The temperature and humidity control of the computer room follows unified industry norms, and is mainly based on the official standards of ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) to establish a strict and standardized environmental control system to eliminate the hidden dangers of equipment operation caused by random regulation.
Data center standard temperature range and influencing factors
According to the ASHRAE standard, the temperature control requirements of Class A1 servers and storage equipment in the computer room are the most stringent.The operating temperature of the computer room is 18℃-27℃, and the optimal temperature control range for medium and large data centers is 20℃-24℃; the equipment can withstand a temperature of 15℃-40℃ for a short time, and long-term critical temperature operation will accelerate hardware aging and increase the risk of failure and downtime.
The temperature control of the computer room needs to be dynamically adapted, which is the core of the precise control of CRAC, and is mainly affected by four factors：
- Equipment installed density: conventional server temperature control pressure is low, AI and GPU high-density equipment consumes 30-50kW in a single cabinet, and a single Feynman GPU consumes 4.4kW. Ultra-high thermal density requires higher responsiveness to air conditioning, refrigeration and temperature regulation.
- System cooling load: Refrigeration energy consumption accounts for 30%-40% of the total power consumption of the data center. It accurately matches the cooling and equipment heat load, which can avoid high temperature downtime, reduce energy consumption and waste, and take into account stable operation and energy saving.
- Air flow design of the computer room: Through the optimization of space blocking, isolation of hot and cold channels, and overhead air supply, the air flow utilization rate is increased by 28%, and the hot air reflux rate is reduced by 40%, which can effectively eliminate dead ends in heat dissipation and uneven heat and cold.
- Cabinet layout planning: standardized hot and cold channel layout relies on overhead floor air supply and hot air reflux refrigeration circulation. Regular cabinet arrangement can ensure smooth air flow and avoid heat accumulation and local overheating.
Computer room humidity standards and dry and wet imbalance hazards
Humidity is an easily overlooked but vital environmental indicator of the computer room. ASHRAE clearly STIPULATES THAT the optimal relative humidity (RH) of the computer room is 40%-60%, the dew point temperature is controlled at 5.5℃-15℃, and the safe tolerance range is 20%-80%RH.Deviation from the standard humidity range will directly cause irreversible equipment damage, and the harm of dry and wet imbalance is extremely hidden and cumulative.
Hidden dangers of low humidity (dry air): Low air humidity is the core cause of static electricity in the computer room. In a dry environment, static electricity can easily accumulate in equipment housings, cabinets, and personnel’s bodies, causing electrostatic discharge (ESD) problems.Instantaneous electrostatic shock will penetrate precision chips and memory modules, causing garbled data and short-circuited hardware; at the same time, it will accelerate the cracking of thermal conductive materials and cracking of circuit board substrates, greatly reducing the service life of equipment.
Hidden dangers of high humidity (humid air): The harm of high humidity is more direct. In a humid environment for a long time, the metal contacts, solder, and circuit boards of IT equipment will oxidize and corrode, causing poor contact and circuit aging; when hot and humid air comes into contact with low-temperature equipment and air-conditioning pipes, condensation will occur, which directly causes the circuit board to short circuit and the equipment to burn down; long-term high-humidity environments will continue to accelerate the aging of insulation materials and optical devices, and shorten the service life of equipment in all directions.
Core difference between CRAC precision temperature and humidity control and traditional HVAC
Many computer room operation and maintenance misunderstandings lie in the mixed use of ordinary commercial HVAC air conditioners. As everyone knows, traditional comfortable air conditioners are completely unable to adapt to the harsh environment of the computer room. The core difference between the two determines that the data center must be dedicated to CRAC precision air conditioners.：
- Traditional HVAC air conditioners are mainly comfortable for the human body, with a wide temperature control range, frequent start and stop, and lagging response. They are only suitable for low-density and unstable personnel heat dissipation loads, and can be shut down and operated at night and during unmanned hours. At the same time, they have high dehumidification requirements and are suitable for human body heat dissipation and humidification characteristics.The CRAC precision air conditioner is specially customized for IT equipment, and its core advantages are concentrated in four dimensions：
- Extremely fast response ability: it can capture small fluctuations in temperature and humidity in the computer room in real time, and complete the load adjustment in seconds to eliminate temperature and humidity hysteresis deviations, and adapt to the dynamically changing heat load of computing power equipment.
- Ultra-high detection accuracy: equipped with a high-precision sensing module, the temperature control error is ≤±0.5℃, and the humidity control error is ≤±3%RH, which is much higher than the sensing accuracy of ordinary air conditioners.
- Uninterrupted operation throughout the year: it supports continuous and stable operation 24/7/365, without frequent start-stop loss, and perfectly matches the year-round operation mode of the computer room.
- Stable air flow management: exclusive air flow control logic, accurately optimize the circulation of hot and cold air, prevent short circuit and heat accumulation of air flow, and ensure uniform and stable global environment.
How CRAC Systems Achieve Precise Temperature Control
CRAC realizes a high-precision constant temperature of ±0.5℃. It is not a single hardware blessing, but the result of the coordinated operation of the three systems of high-precision sensor acquisition, frequency conversion load regulation, and intelligent algorithm regulation, forming a closed-loop, dynamic and accurate temperature control system.
High-precision temperature sensor
The temperature sensor is the “perceptual nerve” of the CRAC system and the prerequisite for accurate temperature control. Its acquisition accuracy, response speed, and rationality of layout directly determine the temperature control effect.
The modern CRAC system adopts a globally distributed sensing layout, deploying sensors at multiple points in the air inlet of the cold channel equipment, the return air zone of the hot channel, the upper and lower floors of the cabinet, and the interior of the air-conditioning unit to map the global thermal distribution of the computer room in real time, and the data acquisition interval is shortened to the second level, which can capture local temperature rise, thermal dead ends and other anomalies in the first time.
Relying on a closed-loop feedback control mechanism, the controller compares the temperature collected by the sensor with the set standard value in real time. Once there is a deviation, it immediately adjusts the operating state of the compressor, fan, and valve, and continuously corrects the temperature parameters to completely eliminate the disadvantages of “large fluctuations, start-stop temperature control” of traditional air conditioners.At the same time, the scientific hierarchical layout strategy can accurately identify the vertical temperature difference and regional temperature difference of the cabinet to ensure the global temperature balance of the computer room.
Variable capacity refrigeration technology
The IT load of the computer room changes dynamically with the fluctuation of business computing power, and the fixed cooling power cannot be adapted to the dynamic demand, which is prone to subcooling and overheating problems.CRAC is equipped with three large-capacity core technologies to achieve accurate output of cooling capacity on demand：
- Frequency conversion compressor: Abandon the traditional fixed-frequency compressor “full on/full off” mode, continuously adjust the refrigerant flow through inverter technology, match the refrigeration power according to the real-time heat load, completely eliminate temperature fluctuations, and significantly reduce energy consumption during low-load periods.
- Electronic expansion valve (EEV): Replaces the traditional thermal expansion valve, accurately regulates the refrigerant delivery volume through a stepper motor, and dynamically fine-tunes based on the superheat data of the evaporator to adapt to the refrigeration needs of the full load interval, and improves the efficiency of the refrigeration cycle and the accuracy of temperature control.
- Frequency conversion drive technology (VFD): Stepless adjustment of the operating speed of the fan and water pump, following the law of cubic loss of fan power, reducing the speed at low load can reduce energy consumption by more than 87.5%, ensuring stable air flow while achieving energy saving and consumption reduction.
- The synergy of the three major technologies allows the CRAC system to get rid of the fixed operating mode and realize the dynamic adaptation of “how much load and how much cooling capacity”, taking into account precise temperature control and high efficiency and energy saving.
Intelligent control algorithm
Hardware is the foundation, and algorithms are the core.Modern CRAC systems rely on intelligent control algorithms to get rid of traditional fixed logic regulation and realize adaptive and predictive temperature control optimization.
- PID precise control algorithm: As the core basic algorithm of CRAC, the temperature deviation is corrected in real time through the three-dimensional calculation of proportional, integral, and differential: the proportional module responds to the instantaneous temperature difference, the integral module eliminates the steady-state error, and the differential module predicts the temperature change trend, and accurately locks the temperature of the computer room within the range of ±0.5℃ of the set value.
- Intelligent scheduling and load prediction: The system can remember the business operation laws of the computer room, and preset cooling strategies in advance for timed batch computing power tasks and seasonal environmental changes; combined with LSTM timing neural networks and enhanced learning AI models, it can predict minute-level and hour-level heat load changes in advance, and realize active temperature adjustment instead of passive error correction.
- Fully automatic adaptive adjustment: No manual intervention is required. The controller can automatically optimize the compressor speed, fan air volume, and valve opening based on the real-time data of the sensor, dynamically balance the temperature control accuracy and energy consumption, and adapt to various complex computer room operation scenarios.
Humidity Precision Control Technologies in CRAC Units
Compared with temperature control, the humidity control of the computer room is more difficult, and it is necessary to achieve two-way precise adjustment of humidification and dehumidification, while avoiding mutual interference between temperature and humidity.Through independent humidification system, intelligent dehumidification module, and high-precision humidity monitoring equipment, CRAC realizes stable humidity control of 40%-60% RH, and the error is controlled at ±2%-3%RH.
Mainstream humidification system
The core of the CRAC humidification system is fast, uniform, and impurity-free humidification. The mainstream is divided into three types: steam type, electrode type, and ultrasonic type, which are suitable for computer room scenarios of different sizes and different energy consumption requirements.：
- Steam humidification: pure steam is generated through the built-in boiler and directly fed into the air supply. The humidity control accuracy is extremely high, there is no mineral pollution, and the response speed is fast. It is the preferred solution for large enterprise data centers. The only shortcoming is the relatively high energy consumption.
- Electrode humidification: the use of water bodies to conduct electricity, heat and boil steam to produce steam, the steam production volume is adaptively adjusted with the current, with self-regulating characteristics, moderate energy consumption, high cost performance, widely used in small and medium-sized server rooms, only need to clean up the electrode scale regularly.
- Ultrasonic humidification: The water body is atomized into ultra-fine water mist through high-frequency vibration, which evaporates and humidifies quickly. The energy-saving effect is outstanding (90% energy-saving compared to steam humidification), and the operation and maintenance cost is low. It is suitable for energy-saving computer rooms. It needs to be used with demineralized water to avoid residual dust from water mist.
Intelligent dehumidification technology
The dehumidification core of the computer room relies on the condensation and dehumidification technology of the cooling coil. When hot and humid air flows through the evaporator coil at a temperature below the dew point, the water vapor will quickly condense into liquid water, which is discharged through the drainage system, and the dual functions of cooling and dehumidification are completed simultaneously.
There are natural shortcomings in this technology: the dehumidification process will simultaneously reduce the air temperature, which is prone to the problem of ”excessive dehumidification and low temperature”.For this reason, CRAC is equipped with a reheating control system, and after dehumidification is completed, it is reheated by electric heating or hot air coil.
Raise the air temperature to the set standard, realize independent control of temperature and humidity, and completely solve the problem of temperature and humidity coupling interference.At the same time, it is equipped with a complete condensate collection, discharge, and monitoring system to investigate hidden dangers of stagnant water and blockage in real time, and eliminate the risk of mold and water leakage.
High-precision humidity monitoring and calibration
The stability of the humidity sensor directly determines the humidity control accuracy. Compared with the temperature sensor, the humidity sensor element is susceptible to pollution, aging, and numerical drift. Therefore, accurate monitoring is inseparable from a perfect calibration and operation and maintenance system.
The mainstream of the industry adopts capacitive polymer humidity sensors, with a response speed of only 10-30 seconds, which can quickly capture humidity fluctuations.In order to ensure long-term accuracy, an annual multi-point calibration mechanism needs to be implemented to verify and correct in the standard range of 25%, 50%, and 75% RH to offset component drift errors.At the same time, through dust protection, multi-point redundant monitoring, and data cross-verification, measurement errors caused by installation dead ends and environmental interference are avoided, and humidity monitoring is accurate and reliable for a long time.
Key Components Enabling CRAC Precision Control
The high-precision operation effect of CRAC is inseparable from the collaborative support of the three core hardware of the controller, the wind pressure and air flow sensor, and the intelligent communication protocol to build a complete intelligent system of “perception-analysis-regulation-transmission”.
Intelligent HVAC controller
The controller is the core center of the CRAC system, co-ordinating all sensor data acquisition, algorithm operation, equipment control, and alarm management, and its four core functions ensure the stability of the computer room environment.：
- Precise temperature and humidity control: dynamically adjust the cooling, heating, humidification, and dehumidification output to stably maintain the constant temperature and humidity of the computer room；
- Hierarchical alarm and early warning: support custom three-level alarm thresholds for early warning, failure, and emergency, and automatically push reminders when the environment is abnormal to avoid risks in advance；
- Remote operation and maintenance control: support network remote viewing of operating data, adjusting equipment parameters, troubleshooting equipment failures, and adapting to unattended computer room operation and maintenance scenarios；
- Zoning differentiated control: according to the differences in heat loads in different areas of the computer room and different cabinets, exclusive control strategies can be customized to eliminate local environmental imbalances.
Wind pressure and airflow sensor
Air flow disorder and wind pressure imbalance are the core causes of local high temperature and high energy consumption in the computer room.The differential pressure sensor monitors the pressure difference between the overhead air supply layer and the computer room and the hot and cold passages in real time, accurately judges the air flow leakage, blockage, and short circuit problems, and guides the operation and maintenance personnel to optimize the layout of the wind panel and block the air leakage points.
With the isolation technology of hot and cold channels, the sensor can feedback the air circulation efficiency in real time, linkage the fan frequency conversion and speed regulation, accurately distribute the flow direction of cold air, eliminate the reflux of hot air and waste of cold air, and maximize the global cooling uniformity and heat dissipation efficiency.
Intelligent communication protocol
The modern CRAC system is compatible with a number of common communication protocols in the industry, and can be seamlessly integrated with the building management system (BMS) and the data center infrastructure management platform (DCIM) to meet the needs of integrated centralized control of smart computer rooms. The core advantages and application scenarios of each protocol are as follows：
- Modbus protocol: extremely versatile, supports dual transmission modes of serial port and Ethernet, can efficiently synchronize equipment temperature and humidity, operating status and fault alarm data, and is suitable for most computer room equipment docking scenarios；
- BACnet protocol: ASHRAE’s official exclusive building automation standard, which can realize the linkage and coordination of CRAC equipment and building facilities such as fire protection, lighting, and security, and build a global intelligent control system；
- SNMP protocol: deeply adapted to the IT operation and maintenance system, supports unified monitoring with core IT equipment such as servers, switches, UPS, etc., breaks through the barriers between facility operation and maintenance and IT operation and maintenance data, and realizes the integrated management of the whole area of the computer room.；
- IoT Internet of Things protocol: supports real-time upload of cloud data, remote device control, and second-level warning of anomalies, which is perfectly adapted to the intelligent operation and maintenance needs of distributed computer rooms and unattended data centers.
Challenges in Maintaining Temperature and Humidity Accuracy
Even if the hardware configuration is up to standard, the complex operation scenarios of the computer room will still bring many control problems. Dynamic load changes, sensor accuracy attenuation, energy efficiency and stability balance are the three core challenges of current operation and maintenance.
Dynamic heat load fluctuation
The heat load of the traditional computer room is relatively stable, but the current popularity of AI computing power, big data, and cloud computing services, GPU high-density cabinets, and instantaneous peak computing power tasks have greatly increased the fluctuation of the heat load of the computer room.
The power of the cabinet has soared from the traditional 5-10kW to 30-50kW, the instantaneous temperature rise speed is fast, and the local heat density is extremely high, which puts forward higher requirements for the response speed and dynamic adjustment ability of the CRAC system, and the traditional fixed control logic is prone to local heat accumulation.
Sensor deviation and installation problems
The sensor is an easy-to-wear component, and performance attenuation will occur during long-term operation: the humidity sensor drifts by 1%-2% RH per year, and the temperature sensor will also have numerical deviations due to dust and oil pollution.
At the same time, the sensor is installed in the wrong location such as the direct air supply area, the dead angle of the air flow, and the heat source of the equipment, which will cause the collected data to fail to truly reflect the air inlet environment of the cabinet, causing problems such as misalignment and over-regulation of the air conditioner, which will affect the safety of the equipment for a long time.
Difficulties in balancing energy efficiency and stability
The PUE value of the data center has stagnated at 1.55-1.59 for a long time, and energy saving and cost reduction have become the core needs of the industry.Two dilemmas often arise in operation and maintenance: adjusting the set value of high temperature and humidity can reduce refrigeration energy consumption, but it will compress the safe operation margin of the equipment. Once the equipment fails and the load increases sharply, it can easily cause thermal downtime；
Although strict control of the environment can ensure stability, it will significantly increase the energy consumption of operation and maintenance.How to accurately balance equipment safety, operating stability and energy-saving costs is the core difficulty of computer room operation and maintenance.
How to Choose a CRAC System with Accurate Temperature and Humidity Control
High-quality CRAC equipment is the core of the stable environment of the computer room. The selection needs to be combined with load requirements, control performance, reliability, and operation and maintenance costs to avoid low-cost and low-configuration, functional redundancy and other issues.
Accurate accounting of cooling capacity
Priority is given to statistics of the total IT equipment power consumption and space area of the computer room, combined with auxiliary loads such as lighting and wall heat dissipation, to accurately match the cooling capacity of CRAC.The core principle of selection: On the basis of the current total heat load, reserve 20%-30% of the capacity for redundancy, adapt to the needs of later equipment expansion and computing power upgrade, and avoid insufficient equipment performance and repeated transformation in the short term.
Focus on core control parameters
Focus on verifying the four core configurations to directly determine the control accuracy: ±0.5℃ high-precision temperature control, ±2%-3%RH high-precision humidity control sensor module; programmable controller with PID intelligent algorithm; frequency conversion compressor, VFD fan, electronic expansion valve full frequency conversion configuration; support Modbus, BACnet, IoT cloud remote monitoring functions, all-round guarantee of accurate control and intelligent operation and maintenance.
Equipment reliability and operation and maintenance convenience
The computer room equipment operates all year round, and reliability is of the utmost importance.Give priority to models that support 24/7 continuous operation, equipped with dual power supplies, redundant fans and other backup structures; verify the service life of core components such as compressors, fans, and humidification modules; give priority to brands with strong versatility of accessories and perfect local after-sales service to reduce late operation and maintenance costs and shorten the time for emergency repairs.
Conclusion
Accurate temperature and humidity control of the computer room can ensure the stability of the equipment, energy saving and longevity.Compared with traditional HVAC, CRAC precision air conditioning has a higher degree of accuracy, stability and intelligence, and can be adapted to the harsh environment of modern computer rooms.
With the popularity of AI and high-density computing power equipment, the heat dissipation pressure in the computer room has increased sharply, and intelligent energy-saving CRAC has become the mainstream.Combining standardized operation and maintenance with DCIM intelligent control, it can avoid equipment failures and optimize PUE, which is an important guarantee for computing power infrastructure.
