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AISLE CONTAINMENT
So, before we go any further, it’s important to note that the
first step in maximising your containment is to understand
the utilisation of the computer room cooling infrastructure;
this is easily done by calculating your computer room’s
Cooling Capacity Factor (CCF). CCF is the ratio of the total
rated cooling capacity of running cooling units to the
estimated heat load. Armed with this knowledge, you’ll
be able to make informed decisions about maximising the
benefits of containment solutions in your facility.
In addition, it’s important to consider the effects of
containment on bypass airflow. Bypass airflow occurs when
the total flow rate of air through all cooling units exceeds
the flow rate of air through IT equipment. Implementation
of containment alone doesn’t reduce the volumetric flow
rate of bypass airflow in a computer room. Instead, if
implemented well, containment creates an environment
where cooling unit fan speeds can be reduced or cooling
units turned off to reduce bypass airflow rates. These
adjustments are necessary to realise the benefits of
reducing fan energy and increasing return temperatures,
which increase the sensible cooling capacity of cooling units
and partial economisation hours of any free cooling systems.
structures, typically abutting the ceiling where fire
suppression is installed, isn’t creating separate
volumes, but merely creating obstructions which need
to meet clearance requirements from sprinkler heads.
With a well-designed space, it’s conceivable that a
standard grid fire suppression system could be installed
around a hot aisle containment array of barriers and
meet code.
Hot aisle containment challenges:
•
Requires a contained path for air to flow from the hot
aisle all the way to cooling units. Often a drop ceiling is
used as return air plenum.
•
Generally, more expensive.
•
High temperatures in the hot aisle create
uncomfortable conditions for technicians working on
IT gear. Note that some server manufacturers are
developing and supplying front-serviceable servers,
which means that the hot aisle, whether contained or
not, would hardly ever need to be entered.
Maximising the benefits
Whether your strategy is to contain the hot or the cold
aisle, airflow containment solutions are a best practice for
managing IT intake temperatures with maximum efficiency.
However, even after containment strategies have been
implemented, many sites fail to take full advantage of the
efficiency and cost-savings containment can provide.
Other considerations
Aside from hot aisle versus cold aisle containment, data
centres have two other options to consider: full versus
partial containment and hard versus soft containment.
Full containment completely encloses the open area of
an aisle while partial containment focuses on creating a
sufficient barrier, or separation between hot and cold air
flows to enable cooling optimisation without causing the
fire suppression challenges inherent with full containment.
Partial containment has been growing in popularity in recent
years for its lower cost, flexible and non-intrusive design, as
well as an increasing awareness of airflow management
fundamentals.
Hard containment is understood as doors, baffles,
partitions, or other rigid components, while soft containment
primarily refers to aisle-end or over-cabinet curtains. For a
number of reasons such as aesthetics and effectiveness,
hard containment tends to be a preference over soft
containment. Facilities should determine which containment
options are appropriate depending on the layout of the
computer room, available budget, and long-term goals.
The best strategy
The fact of the matter is, that each and every computer
room is unique. Whether it be hot or cold aisle containment,
full or partial containment, or hard or soft containment; each
computer room may reveal conditions that will make one
strategy/option more suitable than another. The best thing
to do is to first evaluate your site and calculate the CCF of
the computer room. Then understand the unique layout and
architecture of each computer room to reveal conditions
that make certain containment options preferable. You'll
then be able to choose the best containment option for
your computer room. Once containment is installed, be sure
to consider bypass airflow as you optimise for maximum
efficiency and cooling capacity benefits. n
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