Data Center Cooling Challenges by PTS Data Center Solutions, Inc.
Data Center Educational Resources & Information
The Challenges of Data Center Cooling
Mission critical installations face a number of cooling system challenges in the modern data center. The requirements of today's IT systems, combined with the way those IT systems are deployed, has created new cooling related problems. These are new problems which could not have been foreseen when the data center cooling principles were developed over 30 years ago.
Core challenges in the data center cooling process can be grouped in the following categories:
- Lifecycle Costs
For many companies, meeting adaptability requirements remains the biggest challenge regarding data center cooling systems. Specifically, this involves problems with the cooling of high density rack systems, and the uncertainty of the quantity, timing, and location of high density racks. Data center cooling is further complicated by IT refreshes that typically occur every 1.5 to 2.5 years.
The cooling system within a data center should be flexible and scalable with redundant cooling features to guarantee steady performance. The data center cooling requirements in regard to lifecycle cost challenges share many features in common with adaptability solutions. Pre-engineered, standardized, and modular solutions are typically needed.
PTS' expertise is a valuable asset in this area as companies are often unable to predict if their data center cooling system will supply a future load, even when the characteristics of the load are known in advance. If your company is looking to establish a cooling system for your data center that will withstand system failures and load increases, contact PTS as the next step in your process.
PTS approaches data center cooling designs using
our proven project process:
Design goals are established across the following categories:
Back to the Top
Once appropriate design goals are established there are a number
of additional steps recommended for data center cooling best
Determine the Critical Load and Heat Load.
Determining the critical heat load starts with the
identification of the equipment to be deployed
within the space. However, this is only part of the
entire heat load of the environment. Additionally,
the lighting, people, and heat conducted from the
surrounding spaces will also contribute to the
overall heat load. As a very general rule-of-thumb,
consider no less than 1-ton (12,000 BTU/Hr / 3,516
watts) per 400 square-feet of IT equipment floor
Establish Power Requirements on a per RLU Basis.
Power density is best defined in terms of rack or
cabinet foot print area since all manufacturers
produce cabinets of generally the same size. A
definite Rack Location Unit (RLU) trend is that
average RLU power densities are increasing every
year. The reality is that a computer room usually
deploys a mix of varying RLU power densities
throughout its overall area. The trick is to provide
predictable cooling for these varying RLU densities
by using the average RLU density as a basis of the
design while at the same time providing adequate
room cooling for the peak RLU and non-RLU loads.
Determine the CFM Requirements for each RLU.
Effective cooling is accomplished by providing both
the proper temperature and an adequate quantity of
air to the load. As temperature goes, the American
Society of Heating, Refrigerating, and
Air-Conditioning Engineers (ASHRAE) standard is to
deliver air between the temperatures of 68 °F and 75
°F to the inlet of the IT infrastructure. Although
electronics performs better at colder temperatures
it is not wise to deliver lower air temperatures due
to the threat of reaching the condensate point on
equipment surfaces. Regarding air volume, a load
component requires 160 cubic feet per minute (CFM)
per 1 kW of electrical load. Therefore, a 5,000-watt
1U server cabinet requires 800 CFM.
Perform Computational Fluid Dynamic (CFD)
Modeling. CFD modeling can be performed for the
under floor air area as well as the area above the
floor. CFD modeling the airflow in a computer room
provides information to make informed decisions
about where to place CRAC equipment, IT-equipment,
perforated tiles, high density RLUs, etc. Much of
the software available today also allows mapping of
both under floor and overhead airflow obstructions
to more accurately represent the environment.
Determine the Room Power Distribution Strategy.
The two (2) main decisions in developing a room
power distribution strategy are: (1) Where to place
the power distribution units (PDUs)?, (2) Whether to
run power cables overhead or under the floor?
Determine the Cabinet Power Distribution Strategy.
In deciding how power will be distributed
through the cabinet, use of dual power supplies, and
cabling approach, it is important to understand the
impact of power distribution on cooling,
particularly as it is related to air flow within the
Determine the Room & Cabinet Data Cabling
Distribution Impact. Typically, there are three
(3) choices in delivering network connectivity to an
RLU. They are: (1) Home run every data port from a
network core switch, (2) Provide matching
port-density patch panels at both the RLU and the
core switch with pre-cabled cross-connections
between them, such that server connections can be
made with only patch cables at both ends, (3)
Provide an edge switch at every rack, row, or pod
depending on bandwidth requirements. This approach
is referred to as zone switching.
- Establish a Cooling Zone Strategy.
effective computer room cooling is as much about
removing heat as it is about adding cold. Generally
speaking, the three (3) equipment cooling methods
along with their typical cooling potential can be
determined from the following table:
It is also critical to consider high-density cooling
and zone cooling requirements.
||~2 kW per RLU
||~8 kW per RLU
||~20 kW per RLU
Determine the Cooling Methodology.
determining what cooling zone will be required, the
decision of what types of air conditioners will be
needed, must be made. There are four (4) air
conditioner types: (1) air cooled, (2) glycol
cooled, (3) condenser water cooled, (4) chilled
In addition, it is also important to determine
how heat will be rejected within the system and what
type of cooling redundancy is required and available
for a particular methodology.
the Cooling Delivery Methodology. Different
architectural attributes affect cooling performance
in different ways. For instance, designs should
consider the location of the computer room within
the facility (I.e. onside versus inside rooms),
height of the raised floor, height of suspended
Determine the Floor Plan.
The ‘hot aisle / cold
aisle’ approach is the accepted layout standard for
RLUs for good reason. It works. It was developed by,
Dr. Robert Sullivan, while working for IBM and it
should be adapted for both new and retrofit
projects. After determining the hot/cold
aisles it is critical to place the CRAC units for
peak performance. This may include room, row, or
rack based cooling approaches. Each works well
depending upon the IT infrastructure, power
densities, CFM requirements, and other attributes
Establish Cooling Performance Monitoring.
vital to develop and deploy an environmental
monitoring system capable of monitoring each room,
row, and cabinet cooling zone. A given is that once
effective cooling performance is established for a
particular load profile, it will change rapidly. It
is important to compile trending data for all
environmental parameters for the site such that
moves, adds, and changes can be executed quickly.
To learn more about PTS consulting services to support Air Conditioning Equipment & Systems deployments and support, contact us or visit:
To learn more about PTS recommended Air Conditioning Equipment & Systems, contact us or visit:
Back to the Top