Cooling Audit for Identifying

Potential Cooling Problems in

Data Centers
White Paper 40
Revision 3

by Kevin Dunlap

> Executive summary

The compaction of information technology equipment
and simultaneous increases in processor power consumption are creating challenges for data center
managers in ensuring adequate distribution of cool air,
removal of hot air and sufficient cooling capacity. This
paper provides a checklist for assessing potential
problems that can adversely affect the cooling environment within a data center.

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Cooling Audit for Identifying Potential Cooling Problems in Data Centers

Introduction

There are significant benefits from the compaction of technical equipment and simultaneous
advances in processor power. However, this has also created potential challenges for those
responsible for delivering and maintaining proper mission-critical environments. While the
overall total power and cooling capacity designed for a data center may be adequate, the
distribution of cool air to the right areas may not. When more compact IT equipment is
housed densely within a single cabinet, or when data center managers contemplate largescale deployments with multiple racks filled with ultracompact blade servers, the increased
power required and heat dissipated must be addressed. Blade servers, as seen in Figure 1,
take up far less space than traditional rack-mounted servers and offer more processing ability
while consuming less power per server. However, they dramatically increase heat density.

Figure 1
Examples of compaction

In designing the cooling system of a data center the objective is to create an unobstructed
path from the source of the cooled air to the inlet positions of the servers. Likewise, a clear
path needs to be created from the rear exhaust of the servers to the return air duct of the airconditioning unit. A number of factors that can adversely impact this objective.
In order to ascertain that there is a problem or potential problem with the cooling infrastructure of a data center, certain checks and measurements must be carried out. This audit will
determine the health of the data center in order to avoid temperature-related electronic
equipment failure. They can also be used to evaluate the availability of adequate cooling
capacity for the future. Measurements in the described tests should be recorded and
analyzed using the template provided in the Appendix. The current status should be
assessed and a baseline established to ensure that subsequent corrective actions result in
improvements. This paper shows how to identify potential cooling problems in existing data
centers that will affect the total cooling capacity, the cooling density capacity, and the
operating efficiency of a data center. Solutions to these problems are described in White
Paper 42, Ten Cooling Solutions to Support High-Density Server Deployment.

Check capacity

Remembering that each watt of IT power requires 1 watt of cooling, the first step toward
providing adequate cooling is to verify that the capacity of the cooling system matches the
current and planned power load.
The typical cooling system is comprised of a CRAC (Computer Room Air Conditioner) to
deliver the cooled air to the room and a unit mounted externally to reject the heat to atmosphere. For more information on how air conditioners work and to learn about the different
types, please refer to White Paper 57, Fundamental Principles of Air Conditioners for

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Information Technology and White Paper 59, The Different Types of Air Conditioning
Equipment for IT Environments. Newer forms of CRAC units are appearing on the market
that can be positioned closer (or even inside) data racks in very high-density situations.
In some cases, the cooling system may have been oversized to accommodate a projected
future heat load. Over sizing the cooling system leads to undesirable energy consumption
that can be avoided. For more on problems caused by sizing refer to White Paper 25,
Calculating Total Cooling Requirements for Data Centers.
Verify the capacity of the cooling system by finding the model nomenclature on or inside each
CRAC unit. Refer to the manufacturer technical data for capacity values. CRAC unit
manufacturers rate system capacity based on the EAT (entering air temperature) and
humidity control level. The controller on each unit will display the EAT and relative humidity.
Using the technical data, note the sensible cooling capacity for each CRAC.
Likewise, the capacity of the external heat rejection equipment should be of equal or greater
capacity than all the CRACs in the room. In smaller packaged systems the internal and
external components are often acquired together from the same manufacturer. In larger
systems the heat rejection equipment may have been acquired separately from a different
manufacturer. In either case they are most likely sized appropriately, however an outside
contractor should be able to verify this. If the CRAC capacity and heat rejection equipment
capacity are different, take the lower rated component for this exercise. (If in doubt when
taking measurements, contact the manufacturer or supplier.)
This will give you the theoretical maximum cooling capacity of the data center. It will be seen
later in this paper that there are a number of factors that can considerably reduce this
maximum. The calculated maximum capacity must then be compared with the heat load
requirement of the data center. A worksheet that allows the rapid calculation of the heat load
is provided in Table 1. Using the worksheet, it is possible to determine the total heat output
of a data center quickly and reliably. The use of the worksheet is described in the procedure
below Table 1. Refer to White Paper 25, Calculating Total Cooling Requirements for Data
Centers for more information.
The heat load requirements identified from the following calculation should always be below
the theoretical maximum cooling capacity. White Paper 42, Ten Cooling Solutions to Support
High-Density Server Deployment provides some solutions when this is not the case.

Table 1
Data center or network room heat output calculation worksheet

Item

Data required

Heat output calculation

Heat output subtotal

IT equipment

Total IT load power in watts

Same as total IT load power in watts

_____________ watts

UPS with battery

Power system rated power in watts

(0.04 x Power system rating) + (0.06 x Total IT

load power)

_____________ watts

Power distribution

Power system rated power in watts

(0.02 x Power system rating) + (0.02 x Total IT

load power)

_____________ watts

Lighting

Floor area in square feet, or

2.0 x floor area (sq ft), or

Floor area in square meters

21.53 x floor area (sq m)

People

Max # of personnel in data center

100 x Max # of personnel

_____________ watts

Total

Subtotals from above

Sum of heat output subtotals

_____________ watts

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Procedure
Obtain the information required in the Data required column. Consult the data definitions
below in case of questions. Perform the heat output calculations and put the results in the
subtotal column. Add the subtotals to obtain the total heat output.

Data definitions
Total IT load power in watts - The sum of the power inputs of all the IT equipment.
Power system rated power - The power rating of the UPS system. If a redundant system is
used, do not include the capacity of the redundant UPS.

Check CRACs

If CRAC units in a data center do not work together in a coordinated fashion they are likely to
fall short of their cooling capacity and incur a higher operating cost. CRAC units normally
operate in four modes: cooling, heating, humidification and dehumidification. While two of
these conditions may occur at the same time (i.e., cooling and dehumidification), all systems
within a defined area (4-5 units adjacent to one another) should always be operating in the
same mode. Uncoordinated CRAC units operating in opposing modes (i.e. dehumidifying
and humidifying), called demand fighting, leads to wasted operating costs and a reduction in
the cooling capacity. CRAC units should be tested to ensure that measured temperatures
(supply & return) and humidity readings are consistent with design values.
Demand fighting can have drastic effects on the efficiency of the CRAC system. If not
addressed, this problem can result in a 20-30% reduction in efficiency which in the best case
results in wasted operating costs and worst case results in downtime due to insufficient
cooling capacity.
Operation of the system within lower limits of the relative humidity design parameters should
be considered for efficiency and cost savings. A slight change in set point toward the lower
end of the range can have a dramatic effect on the heat removal capacity and reduction in
humidifier run time. As seen in Table 2, changing the relative humidity set point from 50% to
45% results in a significant operational cost savings.

The position of the CRAC units relative the aisle is important for air distribution. Depending
on the air distribution architecture, CRAC units should be placed perpendicular to the aisle on
either a cold or hot aisle as shown in Figure 2. When using a raised floor for distribution, the
CRAC units should be placed at the end of the hot aisles. The hot air return path to the
CRAC is directly down the aisle without pulling air over the tops of aisles where the opportunity for air to be re-circulated is increased. With less mixing of the hot air in the room, the
capacity of the CRAC units will be increased by warmer return air temperatures. This could
potentially lead to a requirement for fewer units in the room.

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CRAC

COLD AISLE

HOT AISLE

Hot aisle positioning of CRAC units

CRAC

COLD AISLE

COLD AISLE

Figure 2

HOT AISLE

CRAC

CRAC

When a slab floor is used, the CRAC should be placed at the end of the cold aisle. This will
distribute the supply air to the front of the cabinets. Some mixing will exist in this configuration and it should be implemented only when low power densities per rack exist.

Temperature 72F (22.2C)

Relative humidity set point

50%

45%

Total cooling capacity

48.6 (166,000)

49.9 (170,000)

Table 2

Temperature change (total sensible capacity)

45.3 (155,000)

49.9 (170,000)

Humidification cost
savings example at
lower set point

Humidification requirement
Moisture removed (total latent capacity) (Btu / hr)

3.3 (11,000)

0.0 (0,000)

Lbs / hr (kg / hr) humidification required (Btu /

1074 or kW / 0.3148)

10.24 (4.6]

100.0%

0.0%

3.2

$2,242.56

$0.00

Cooling capacities kW (Btu / hr)

Humidifier runtime
kW required for humidification
Annual cost of humidification (cost per kW x 8760 x
kW required)

Note: Assumptions and specifications for the example above can be found in the Appendix.

Check set points

Set points for temperature and humidity should be consistent on all CRAC units in the data
center. Unequal set points will lead to demand fighting and fluctuations in the room. Heat
loads and moisture content are relatively constant in an area and CRAC unit operation should
be set in groups by locking out competing modes through either a building management
system (BMS) or a communications cable between the CRACs in the group. No two units
should be operating in competing modes during a recorded interval, unless part of a separate

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group. When grouped, all units in a specific group will be operating together for a distinct
zone
Set point parameters should be within the following ranges:

Temperature 68-77F (20-25C)

Humidity 40-55% Relative Humidity
To test the performance of the system, both return and supply temperatures must be
measured. Three monitoring points should be used on the supply and return at the geometric
center as shown in Figure 3.

oints
itor p )
n
o
M
rn
(Retu

Figure 3

oints
itor p )
n
o
M
ply
(Sup

Supply and return temperature

monitoring points
nts
r poi
o
t
i
n
Mo
ply)
(Sup

oints
tor p
Moni turn)
(Re

In ideal conditions the supply air temperature should be set to the inlet temperature required
at the server inlet. This will be checked later by taking temperature readings at the server
inlets. The return air temperature measured should be greater than or equal to the temperature readings from racks and aisles. A lower return air temperature than the temperature in
racks and aisles indicates short cycling inefficiencies. Short cycling occurs when the cool
supply air from the CRAC unit bypasses the IT equipment and flows directly into the CRAC
unit air return duct. See White Paper 49, Avoidable Mistakes that Compromise Cooling
Performance in Data Centers and Network Rooms for information on preventing short cycling.
The bypass of cool air is the biggest cause of overheating and can be caused by a number of
factors.
Also, verify that the filters are clean. Impeded airflow through the CRAC will cause the
system to shutdown on loss of airflow alarm. Filters should be changed quarterly as a
preventative maintenance procedure.

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Test main
cooling circuit

This section requires an understanding of basic air condition equipment. For more information on this read White Paper 59, The Different Types of Air Conditioning Equipment for IT
Environments. Get your maintenance company or an independent HVAC consultant to check
the condition of the chillers (where applicable), pumping systems and primary cooling loops.
Ensure that all valves are operating correctly.

Chilled water cooling circuit

The condition of the chilled water loop supply to the CRACs will directly affect the ability of
the CRAC to supply proper conditioned air to the room or raised floor plenum. To check the
supply temperature, contact your maintenance company or an independent HVAC consultant.
As a quick check, the temperature of the piping supply to the CRAC can be used. Using a
laser thermometer, measure the supply pipe surface temperature to the CRAC unit. In some
cases, gauges may be installed inline with the piping, displaying temperature of the water
supply.
Chilled water piping will be insulated from the air stream in order to prevent condensation on
the pipe surface. For the most accurate measurement, peel back a section of the insulation
and take the measurement directly on the surface of the pipe. If this is not possible, a small
section of piping is likely exposed inside the CRAC unit at the inlet to the cooling coil on the
left or right side of the coil.

Condenser water circuit (water and glycol cooled)

Water and glycol cooled systems utilized a condenser in the CRAC for transferring heat from
the CRAC to the water circuit. Condenser water piping will likely not be insulated due to the
warmer temperatures of the supply water. Measure the supply pipe surface temperature at
the entry point to the CRAC unit. Direct expansion (DX) systems should be checked to
ensure that they are fully charged with the proper amount of refrigerant.

Air cooled refrigerant piping

As with water and glycol cooled CRACs, refrigerant charge should be checked for the proper
levels. Contact your maintenance company or an independent HVAC consultant to check the
condition of refrigerant piping, outdoor heat exchangers and refrigerant charge.
Compare temperatures to those in Table 3. Temperatures that fall outside the guidelines
may indicate a problem with the supply loop.

Chilled water

Condenser water
(water cooled)

Condenser water
(glycol cooled)

45F (+/- 3F)

Max 90F

Max 110F

7.2C (+/- 1.7C)

Max 32.2C

Max 43.3C

Table 3
Supply loop temperature
tolerances

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Record rack
and aisle
temperatures

By recording the temperature at various locations between rows of racks, a temperature

profile is created which helps diagnose potential cooling problems and ensures that cool air is
supplied to critical areas. If the aisles of racks are not properly positioned hot spots can
occur in various locations and may cause multiple equipment failures. The section on aisle
and floor tile arrangement describes and illustrates a best practice for rack layouts. Take
room temperatures at strategic positions within the aisles of the data center. 1 These
measuring positions should generally be centered between equipment rows and spaced at
approximately one point at every fourth rack position as shown in Figure 4.

Figure 4
ASHRAE TC9.9 hot aisle / cold
aisle measurement points

Reprinted with permission ASHRAE 2004. (c) American Society of Heating, Refrigerating and AirConditioning Engineers, Inc., www.ashrae.org.

Aisle temperature measurement points should be 5 feet (1.5 meters) above the floor. When
more sophisticated means of measuring the aisle temperatures are not available this should
be considered a minimal measurement. These temperatures should be recorded and
compared with the IT equipment manufacturers recommended inlet temperatures. When the
recommended inlet temperatures of IT equipment are not available, 68-75F (20-25C)
should be used in accordance to the ASHRAE standard. Temperatures outside this tolerance
can lead to a reduction in system performance, reduced equipment life and unexpected
downtime. Note: All the above checks and tests should be carried out quarterly. Temperature checks should be carried out over a 48-hour period during each test to record maximum
and minimum levels.

Poor air distribution to the front of a rack can cause the hot exhaust air from the equipment to
recirculate back into the intakes. This causes some equipment, typically those mounted
toward the top of the rack, to overheat and shutdown or fail. This step is to verify that the
bulk inlet temperatures in the rack are adequate for the equipment installed. Take and record
temperatures at the geometric center of the rack front at bottom, middle and top as illustrated
in Figure 5. When the rack is not fully populated with equipment, measure inlet temperatures
at the geometric center of each piece of equipment. Refer to the guidelines under check
CRACs for acceptable inlet temperatures. Temperatures not within the guidelines represent
a cooling problem for that monitoring point.
Monitoring points should be 2 inches (50 mm) off the face of the rack equipment. Monitoring
can be accomplished with thermocouples connected to a data collection device. Monitoring
1

ASHRAE Standard TC9.9 gives more details of positioning sensors for optimum testing and recommended inlet temperatures. ASHRAE (American Society of Heating, Refrigeration and Air-Conditioning
Engineers http://www.ashrae.org)

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points may also be measured by using a laser thermometer for quick verification of temperatures as a minimal method.

Monitor points
Figure 5
ASHRAE monitoring points for
equipment inlet temperatures

Reprinted with permission ASHRAE 2004. (c) American Society of Heating, Refrigerating and AirConditioning Engineers, Inc., http://www.ashrae.org.

Check airflow
from floor grilles

It is important to understand that the cooling capacity of the cabinet is directly related to the
airflow volume delivery stated in CFM (cubic feet per minute). IT equipment is designed to
raise the temperature of the supply air by 20-30F (11-17C). Using the equation for heat
removal, the amount of airflow required at a given temperature rise can be quickly computed.
CFM or m3/s = the volume of airflow required to remove the heat generated by IT equipment
Q = the amount of heat to be removed expressed in kilowatts (kW)
F or C = the exhaust air temperature of the equipment minus the intake temperature

CFM =

3,412 Q
1.085 F

m3 / s =

Q
1.21 C

For example, to calculate the airflow required to cool a 1 kW server with a 20F temperature
rise:

CFM =

3,412 1kW
= 157.23
1.085 20F

m3 / s =

1kW
= 0.0742
1.21 11C

Therefore, for every 1 kW of heat removal required at a design DeltaT (temperature rise
through IT equipment) of 20F (11C) you must supply approximately 160 cubic feet per
minute (0.076 m3/s or 75.5 L/s) of conditioned air through the equipment. When calculating
the necessary airflow requirement per rack, this can be used as an approximated design

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value. However, adherence to the manufacturer name plate requirements should be
followed.

(m 3 / s ) / kW = 0.074

CFM / kW = 157.23

( L / s ) / kW = 74.2

Using the design value and the typical tile (~ 25% open) airflow capacity shown in Figure 5
below, the max power density per cabinet should be 1.25 to 2.5 kW per cabinet. This is
applicable to installations utilizing one tile per cabinet. In instances where cabinet to floor tile
ratio is greater than one, the available cooling capacity should be divided among the cabinets
in the row.

Testing the airflow of a vented floor tile

Figure 6
Available rack
enclosure cooling
capacity of a floor tile
as a function of pertile airflow

Cooling Capacity per Tile (kW)

Measuring the amount of available cooling capacity on a given floor tile can be accomplished
simply laying a small piece of paper on it. If the paper gets sucked into the floor tile this
means that air is being drawn back under the raised floor which indicates a problem with the
rack and CRAC positioning. If the paper is unaffected it could be that there is not air getting
to that tile. If the paper moves up off the floor tile this is an indication that air is being
distributed from that tile. However, depending on the power density of the equipment being
cooled, the amount of air from the tile may not be enough. In this case a grate or air distribution device may be required to allow more air to flow to the front of the racks.

With
Effort

Typical
Capability

Extreme

Impractical

5
4
3
2
1
0
0

100
[47.2]

200
[94.4]

300
[141.6]

400
[188.8]

500
[236.0]

600
[283.2]

700
[330.4]

800
[377.6]

900
[424.8]

1000
[471.9]

Tile Airflow (CFM) [ L/s ]

Inspect
enclosures

Unused vertical space within rack enclosures causes the hot air output from equipment to
take a short circuit back to the inlet of the equipment. This unrestricted cycling of hot air
causes the equipment to heat up unnecessarily which can lead to equipment damage or
downtime. The use of blanking panels to combat this effect is described in more detail in
White Paper 44, Improving Rack Cooling Performance Using Blanking Panels. Visually
examine each rack. Are there any gaps in the u positions? Are CRT monitors being used?
Are blanking panels installed in these racks? Is an excess of cabling impeding the airflow?
If there are visible gaps in the U space positions, blanking panels are not installed or there is
excessive cabling in the rear of the rack, then airflow within the rack will not be optimal as
illustrated in Figure 7.

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Figure 7

Side

Side

Diagrams of rack airflow showing

effect of blanking panels

7A (left)

Blanking Panel

Without blanking panels

7B (right)
With blanking panels

Check aisle, floor

tiles, and air
paths

Check sub-floors for cleanliness and / or obstructions. Any dirt and dust present below the
raised floor will be blown up through floor grills and will be drawn into the IT equipment. Floor
obstructions such as network and power cables will obstruct airflow and have a negative
effect on the cooling supply to the racks.
Subsequent addition of racks and servers will result in the installation of more power and
network cabling. Often, when servers and racks are moved or replaced, the redundant
cabling is left beneath the floor.
A visual inspection of the floor surface should be conducted when a raised floor is utilized for
air distribution. Voids, gaps and missing floor tiles have a damaging effect on the static
pressure of the floor plenum. The ability to maintain airflow rates from perforated floor tiles
will be diminished with the presence of unsealed areas on the raised flooring.
Missing floor tiles should be replaced. The floor should consist of solid or perforated floor
tiles in every section of the grid. Holes in the raised flooring tiles used for cabling access
should be sealed using brush strips or other cable access products. Measurements
conducted show that 50-80% of available cold air escapes prematurely through unsealed
cable openings.
With few exceptions, most rack-mounted servers are designed to draw air in at the front and
exhaust at the back. With all the racks facing the same way in a row, the hot air from row
one is exhausted into the aisle where it will mix with supply or room air and then enter into
the front of the racks in row two. This arrangement is shown in Figure 8. As air passes
through each consecutive row the IT equipment is subjected to hotter intake air. If all the
rows have the cabinets arranged so that the inlets of the servers face the same direction
equipment malfunction is imminent.

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Figure 8
Rack arrangement with no
separation of hot or cold aisles

Configuring the rack in a hot aisle / cold aisle configuration will separate the exhaust air from
the server inlets. This will allow the cold supply air from the floor tiles to enter into the
cabinets with less mixing as illustrated in Figure 9 below. For more on air distribution
architectures in the data center refer to White Paper 55, Air Distribution Architecture for
Mission Critical Facilities.

Figure 9
Hot aisle / cold aisle rack
arrangement

Improper location of these vents can cause CRAC air to mix with hot exhaust air before
reaching the load equipment, giving rise to the cascade of performance problems and costs
described previously. Poorly located delivery or return vents are very common and can erase
almost all of the benefit of a hot aisle / cold aisle design.

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Conclusion

Routine checks of a data centers cooling system can identify potential cooling problems early
on to help prevent downtime. Changes in power consumption, IT refreshes and growth can
change the amount of heat produced in the data center. Regular health checks will most
likely identify the impact of these changes before they become a major issue. Achieving the
proper environment for a given power density can be accomplished by addressing the
problems identified through the health checks provided in this white paper. For more
information on cooling solutions for higher power densities refer to White Paper 42, Ten
Cooling Solutions to Support High-Density Server Deployment.

About the author

Kevin Dunlap is the Product Line Manager for modular / high density cooling solutions at
Schneider Electric. Schneider Electric is a global leader in the development of precision power
system technologies and one of the world's largest providers of equipment that serves the
network-critical physical infrastructure. Involved with the power management industry since
1994, Kevin previously worked for Systems Enhancement Corp., a provider of power management hardware and software, which APC acquired in 1997. Following the acquisition, Kevin
joined APC as a Product Manager for management cards and then precision cooling solutions
following the acquisition of Airflow Company in 2000.
Kevin has participated on numerous power management and cooling panels, as well as on
industry consortiums and ASHRAE committees for thermal management and energy efficient
economizers.

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Resources
Ten Cooling Solutions to Support High-Density
Server Deployment
White Paper 42

Fundamental Principles of Air Conditioners for

Information Technology
White Paper 57

The Different Types of Air Conditioning Equipment

for IT Environments
White Paper 59

Calculating Total Cooling Requirements for Data Centers

White Paper 25

Avoidable Mistakes that Compromise Cooling Performance

in Data Centers and Network Rooms
White Paper 49

Air Distribution Architecture for Mission Critical Facilities

White Paper 55

Comparing UPS System Design Configurations

White Paper 44

Browse all
white papers
whitepapers.apc.com

Browse all
TradeOff Tools

2014 Schneider Electric. All rights reserved.

tools.apc.com

Contact us
For feedback and comments about the content of this white paper:
Data Center Science Center
dcsc@schneider-electric.com
If you are a customer and have questions specific to your data center project:
Contact your Schneider Electric representative at
www.apc.com/support/contact/index.cfm

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Appendix

Assumptions and specifications for Table 2

Both scenarios in the humidification cost savings example in Table 2 are based on the
following assumptions:

50 kW of electrical IT loads which results in approximately 50 kW of heat dissipation

Air temperature returning to CRAC inlet is 72F (22.2C)
Based on 1 year operation (7x24) which equates to 8,760 hours
CRAC unit volumetric flow of 9,000 CFM (4.245 m3/s)
Ventilation is required but for simplification it was assumed that the data center is completely sealed - no infiltration / ventilation

Cost per kW / hr was assumed to be $0.08 (U.S.)

CRAC unit specifications based on an APC FM50:
- Standard downflow
- Glycol cooled unit (no multi-cool or economizer)
- Electrode steam generating humidifier (Plastic canister type with automatic water level
adjustment based on water conductivity)
- Humidifier capacity is 10 lbs/hr (4.5 kg / hr)
- Humidifier electrical consumption is 3.2 kW
- Voltage is 208 VAC

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Figure A1
Audit checklist

Cooling Audit Checklist

Capacity Check
CRAC

Model

Unit 1
Unit 2
Unit 3
Unit 4
Unit 5
Unit 6
Unit 7
Unit 8
Unit 9
Unit 10

Total Capacity

Sensible Capacity

Quantity

Total Usable Capacity = SUM (Sensible Capacity x Quantity)

Heat Load Requirement

IT Equipment

Total IT load power in watts

UPS with Battery

Power system rated power in watts

Power Distribution

Power system rated power in watts

Lighting
People
Total

Floor area in square feet, or floor area in square

meters
Max # of personnel in data center
Subtotals from above

Same as total IT load power in watts

(0.04 x Power system rating) + (0.06 x

Total IT load power)
(0.02 x Power system rating) + (0.02 x
Total IT load power)
2.0 x floor area (sq ft), or
21.53 x floor area (sq m)
100 x Max # of personnel
Sum of heat output subtotals
Capacity is equal to or greater than heat output?

Yes

No

CRAC Monitoring Points

Supply (average of three monitoring points for each)
CRAC 1 ________
CRAC 6 ________
CRAC 2 ________
CRAC 7 ________
CRAC 8 ________
CRAC 3 ________
CRAC 9 ________
CRAC 4 ________
CRAC 10________
CRAC 5 ________
Return (average of three monitoring points for each)
CRAC 1 ________
CRAC 6 ________
CRAC 2 ________
CRAC 7 ________
CRAC 8 ________
CRAC 3 ________
CRAC 9 ________
CRAC 4 ________
CRAC 10________
CRAC 5 ________

Acceptable
Meets Tolerance (check one)
Averages: Temp. 68All within range
75F (20-25C),
Humidity 40-55% 1-2 out of range
>2 out of range
R.H.

Acceptable
Averages: Temp. 5865F (14-18C)

Meets Tolerance (check one)

All within range
1-2 out of range
>2 out of range

Cooling Circuits
Chilled Water
Condenser Water - Water Cooled
Condenser Water - Glycol Cooled
Air Cooled

45F (+/- 3F), 7.2C (+/- 1.7C)

Meets Tolerance
Max 90F (32.2C)
(check one)
Max 110F (43.3C)
Should be checked by qualified HVAC contractor

Yes

No

Yes

No

Yes

No

Aisle Temperatures
Measurement points at 5 feet (1.5 meters) above the floor at every 4th rack (averaged for aisle)
Aisle 1 ________
Aisle 6 ________
Acceptable
Aisle 2 ________
Aisle 7 ________
Averages: Temp. 68Aisle 8 ________
Aisle 3 ________
75F (20-25C)
Aisle 9 ________
Aisle 4 ________
Aisle 10________
Aisle 5 ________

Schneider Electric Data Center Science Center

Meets Tolerance (check one)

All within range
1-2 out of range
>2 out of range

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Cooling Audit for Identifying Potential Cooling Problems in Data Centers

Figure A2
Audit checklist (cont.)
Rack Temperatures
Measurement points at 5 feet (1.5 meters) above the floor at every 4th rack (averaged for aisle)
R1 ____ R2 ____ R3 ____
R46 ____ R47____ R48 ____
R4 ____ R5 ____ R6 ____
R49 ____ R50____ R51 ____
R7 ____ R8 ____ R9 ____
R52 ____ R53____ R54 ____
R10 ____ R11____ R12 ____
R55 ____ R56____ R57 ____
Acceptable
R13 ____ R14____ R15 ____
R58 ____ R59____ R60 ____
Averages: Temp. 68R16 ____ R17____ R18 ____
R61 ____ R62____ R63 ____
75F (20-25C), Top
R19 ____ R20____ R21 ____
R64 ____ R65____ R66 ____
to bottom
R22 ____ R23____ R24 ____
R67 ____ R68____ R69 ____
temperatures in
R25 ____ R26____ R27 ____
R70 ____ R71____ R72 ____
each rack should not
R28 ____ R29____ R30 ____
R73 ____ R74____ R75 ____
differ more than 5F
R31 ____ R32____ R33 ____
R76 ____ R77____ R78 ____
(2.8C)
R34 ____ R35____ R36 ____
R79 ____ R80____ R81 ____
R37 ____ R38____ R39 ____
R82 ____ R83____ R84 ____
R40 ____ R41____ R42 ____
R85 ____ R86____ R87 ____
R88 ____ R89____ R90 ____
R43 ____ R44____ R45 ____

Meets Tolerance (check one)

All within range

1-2 out of range

>2 out of range

Airflow
Check all perforated tiles (where applicable), compare to tolerances
Airflow measurement (positive airflow check),
volume tests should be carried out by a qualified
HVAC contractor

Perforated floor tiles

Acceptable
Averages: => 160
cfm/kW
(75.5 L/s) / kW

Meets Tolerance (check one)

All within range
1-2 out of range
>2 out of range

Inspecting the Rack

Are blanking panels installed in all rack spaces where IT equipment is not
installed?

Blanking Panels

Meets Tolerance
(check one)

Yes

No

Yes

No

Yes

No

Yes

No

Yes

No

Yes

No

Air Path Below the Floor (where applicable)

Visible obstructions

Are blanking panels installed in all rack spaces where IT equipment is not
installed?

Missing tiles, gaps and voids

Are all floor tiles in place? Are cable access openings adequately sealed?

Meets Tolerance
(check one)

Aisle and floor tile arrangement

Perforated floor tile positions
CRAC positioning

Are blanking panels installed in all rack spaces where IT equipment is not
Do the CRACs line up with the hot aisles?

Hot aisle, cold aisle layout

Is there separation between hot and cold aisles (racks not facing the same
direction)?

Schneider Electric Data Center Science Center

Meets Tolerance
(check one)

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