By Michael Young, Pr. Eng.

Part four – Increasing operating conditions within a data centre: is it a good or bad thing?

In the pursuit to reduce electrical consumption and expand on the number of hours of ‘free cooling’, there has been an ongoing effort to raise the operating IT temperatures within the data centre.

While it may seem trivial to pay so much attention to operating IT temperatures; performance, noise levels and operating costs of the cooling unit are greatly impacted by this one design parameter.

ASHRAE provided guidance on the operating air conditions of the IT equipment by publishing the ‘Thermal Guidelines for Data Processing Environments’. This document recommended the inlet air condition of dry bulb temperatures and relative humidity (RH) for different types of IT equipment.

According to this guideline, the objective is to raise the operating temperature of the data centre while still ensuring reliability of the IT equipment. Now before the operating temperature of a data centre is raised, it is important to look at a data centre holistically as the system dynamics are complex in that the energy consumption of some systems decrease while others increase.

If a chilled water type of system is used to cool the data centre, raising the IT temperature set point can cause designers to also raise the operating water temperatures of the chiller. This decreases the energy consumed by the chiller as the data centre can operate in ‘free-cooling’ mode for a larger portion of the year and the chiller efficiency increases.

However this isn’t the entire picture, as even though the chiller energy decreases, server energy increases as the server fans operate at higher speeds due to the increase in operating temperature.

This in turn causes the computer room air handler (CRAH) fans to also increase in speed to support the higher server airflow requirements. This means greater CRAH energy consumption.

CRAH units have to increase in size due to a loss of heat transfer between the return air condition and the higher inlet water temperature.

Where space is a constraint, the CRAH unit design is often modified and taller coils are installed within the unit, and supply air fans are required to operate at higher speeds to deliver the increased airflow rates which increases noise levels within the white space.

Therefore, it is important to not only consider the performance of the chiller but also consider the operations of the CRAH unit. Simply increasing the operating temperature of the data centre can sometimes not yield the desired result. Moving forward, the entire system must be analysed to confirm if a higher operating condition has a positive or negative effect for the construction of a data centre at a specific location.   

Join us in our next publication where we will discuss how operating conditions influence the performance and operations of a DX system.

Wishing you a successful month ahead. 

About Michael Young

Michael Young, Pr. Eng.


Michael Young is a trainer, coach and a pre-sales engineer in the HVAC industry. He graduated from the University of the Witwatersrand in the field of Mechanical Engineering (B.Sc Mech Eng) in 2008 and qualified as a Professional Engineer (Pr.Eng) in 2013. Michael is passionate about promoting knowledge and helping other young engineers grow within the industry through his training workshops and coaching sessions.





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