Vertiv Liebert CRV User guide

Liebert® CRV™
Air-Cooled, Water/Glycol-Cooled andChilledWater,
50&60Hz
Application Guide

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TABLE OF CONTENTS
1 What is the Liebert CRV? 5
1.1 Liebert CRV Intended Application 5
2 Liebert CRV Controls 7
2.1 Liebert CRV Sensor Location Guidelines 8
3 General Liebert CRV Guidelines 9
4 Site Application and Unit Placement 11
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1 WHAT IS THE LIEBERT CRV?
The Liebert CRV is a Precision Cooling unit intended to be located within a row of heat-generating IT
equipment racks. The Liebert CRV provides all the necessary functions of a precision air conditioner
including cooling, humidification, dehumidification, air filtration and condensate management. Air enters
the Liebert CRV unit from the hot aisle. The air, filtered, cooled and conditioned, is discharged into the
cold aisle through an adjustable supply air baffle. The supply air baffle allows the air leaving the cooling
unit to be directed to the racks the Liebert CRV is conditioning; maximizing its effectiveness, reducing the
chance for hot spots and improving the overall system efficiency.
The Liebert CRV is optimized for maximum cooling capacity in a minimal footprint. The extremely energy
efficient components of the system are managed by the Liebert iCOM control system. The environment is
monitored in real time by the Liebert iCOM control through sensors positioned in a variety of locations.
Sensors located in the return air, supply air and rack inlets allow the unit to optimize its operations for
both performance and energy efficiency. All unit operations and sensor data can be reported remotely via
a variety of communication protocols, providing end users with a built-in mini-monitoring system.
1.1 Liebert CRV Intended Application
The Liebert CRV can be utilized in a variety of applications. Since the Liebert CRV provides complete
temperature and humidity control along with filtration, it can be deployed as the only cooling unit in small
data centers and network closets. Larger data centers are able to benefit from its standard rack-sized
footprint, deploying it as a supplemental spot cooler to address both hot spots and high-density racks.
The small footprint and variable cooling and airflow allow the Liebert CRV to be initially oversized in
anticipation of future IT expansion without any footprint or energy consumption penalties. The Liebert
CRV can be applied on both raised and non-raised floors, allowing it work with existing under floor and
overhead cooling systems. The Liebert CRV can operate in conjunction with an existing Liebert XD
installation, or provide an excellent alternative for sites that are unable to support a Liebert XD system.
The Liebert CRV is compatible with all types of aisle containment designs; however the Liebert CRV
control algorithms have been optimized for cold-aisle containment.
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Figure 1.1 Liebert CRV—front and rear views
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2 LIEBERT CRV CONTROLS
The Liebert CRV is equipped with the latest in Liebert iCOM controls. Available in every Liebert CRV is a
return temperature and humidity sensor, a supply temperature sensor and three remote rack sensors
with the option to add an additional seven remote rack sensors. Each rack sensor takes two temperature
readings and can be configured to report either the average or the higher of the two sensors.
The Liebert iCOM controller on the Liebert CRV leaves the factory with the fan speed and cooling
capacity controlled by the supply air sensor. This control mode is extremely robust and will ensure
delivery of precise cooling to the cold aisle. To unlock the full capability of the Liebert CRV, remote rack
sensors can be installed, which will allow the fan speed and the cooling capacity to be “decoupled.”
Decoupling means that the fan speed can now be controlled from the remote rack sensors and the
cooling capacity controlled from the supply air sensor. In this advanced configuration, the Liebert CRV
can now control the discharge temperature of the unit by modulating cooling capacity based on the
supply sensor and use the remote rack sensors to ensure that the cool air is being delivered to the inlet of
the racks. Using the supply and remote rack sensors in this decoupled mode is the preferred method for
controlling the Liebert CRV in a hot-aisle/cold-aisle configuration. In addition to this configuration the
Liebert CRV has additional flexibility for other applications that can be understood in Table 2.1 below.
Cooling Capacity
Supply
Air Sensor
Remote
Air Sensor
Return
Air Sensor
Fan Speed
Supply Air Sensor A (Coupled) — —
Remote Air Sensor D (Decoupled) B (Coupled) —
Return Air Sensor E (Decoupled) F (Decoupled) C (Coupled)
Table 2.1 Coupled and decoupled control schemes
Table 2.1 above shows the flexibility of the Liebert CRV and how different sensor locations can be used to
control the Liebert CRV fan speed and cooling capacity. The configurations labeled “A,” “B” and “C” are
defined as coupled control schemes. These coupled control schemes allow both the cooling and fan speed
to be controlled by the same sensor input, either from the supply air sensor, remote air sensor or return air
sensor. Schemes labeled “D,” “E” and “F” are defined as decoupled control schemes. These decoupled
control schemes use separate sensor inputs for controlling the fan speed and cooling. For instance, an
alternate to the factory default control program is “D,” where the fans are controlled by the remote rack-
mounted temperature sensors and the cooling is controlled by the discharge air temperature sensor in
the Liebert CRV.
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2.1 Liebert CRV Sensor Location Guidelines
Three rack sensors come with the Liebert CRV unit to help prevent any problem spots in the row. Rack
sensors help combat cooling problems related to recirculation of air, uneven rack loading and air
distribution. The rack sensors are intended for use in the cold aisle only. To ensure effective cooling
provided by a Liebert CRV, follow these suggestions for locating the rack sensor probes:
•Place on the top of the perforated rack door.
•In front of the highest-mounted servers in the rack.
•In front of the highest-density area of the rack.
•In the airflow path entering the rack.
•Do not place the probe directly on the metal surface of the perforated door.
Additional information about sensor location can be found in the Liebert CRV Installation, Operation and
Maintenance manual, SL-11975, which is available at www.VertivCo.com.
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3 GENERAL LIEBERT CRV GUIDELINES
The Liebert CRV is capable of supporting many varied room configurations. Following a few basic
guidelines, the Liebert CRV can provide efficient and precision cooling to the space and adjacent rack
mounted equipment. The following points are highly effective recommendations for precision
performance and efficient operation of the Liebert CRV in many room layouts:
•Distribute equipment as evenly as possible across the height of the rack.
•Use blanking panels to prevent recirculation of air through gaps in rack equipment.
•Locate racks closely together, preventing gaps between equipment racks.
•Where applicable, use dividers to prevent hot air wrap around to the cold aisle.
•Locate the Liebert CRV appropriately to effectively deliver cooling to the rack row.
The application of a Liebert CRV is meant to provide cooling to between two and six racks of equipment in
a single row. A row of equipment longer than six racks might not receive the appropriate quantity of
conditioned air from a single Liebert CRV unit. The total number of racks that can be cooled will depend
fully upon the rack loads and airflow requirements of the equipment to be cooled, as well as the type and
size of the Liebert CRV selected. In conjunction with Liebert CRV placement, maintaining a cold aisle
between three and four feet wide is highly suggested. This is beneficial because it provides a smaller
volume for conditioned air to inhabit, preventing hot aisle air intrusion. The density of the conditioned air
will help to prevent hot aisle air from recirculating through the rack equipment. Wider cold aisles can be
utilized with cold aisle containment designs, including the Liebert Cold Aisle Containment product line.
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4 SITE APPLICATION AND UNIT PLACEMENT
Scenario 1: Single Equipment Row
The Liebert CRV is intended to cool a single row of racks by providing a curtain of cold discharge air
across the face of the equipment. Ideally the Liebert CRV should be located at the end of the rack row
with a three to four foot cold aisle. Adjustment to the baffle system will allow cooling to be directed down
the row effectively delivering coverage to the rack row.
NOTE: It is not ideal to place the Liebert CRV in the middle of a single rack row. Middle placement may
create hot spots at the top of the rack equipment, due to inconsistent air coverage.
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Scenario 2: Double Equipment Row
When using a Liebert CRV with double rack rows, location of the Liebert CRV unit is similar to the single-
row placement. Locate the Liebert CRVs at opposite ends of the two rows and adjust the air baffles in the
direction of desired cooling. Placing the Liebert CRV at opposite ends of each row will allow the Liebert
CRVs to provide coverage for both rack rows by pressurizing the cold aisle. Increased pressurization in the
cold aisle helps to eliminate any hot spots from developing in the row. Double-row usage simulates a
containment approach. The opposing rack row acts as a wall or partition, helping to contain the provided
cooling in the cold aisle instead of allowing it to spread throughout the space that the equipment is
located.
NOTE: It is not suggested to locate two Liebert CRV units directly across from one another or by
locating two units adjacent to one another in a row. Both situations have potential to reduce the
effective cooling of both Liebert CRV units in the row. If more than one Liebert CRV unit needs to be
placed within a row, separation of at least one rack is recommended.
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Scenario 3: Redundancy
Single-Row Redundancy
Single-row redundancy can be achieved by locating two Liebert CRV units at opposite ends of a row, as
shown. Directing the air baffles toward one another and down the face of the rack row will allow the Liebert
CRV units to operate at partial load while providing the required cooling. If a unit failure should occur, the
remaining unit will ramp up airflow, respond to the higher return air temperature and provide the required
cooling based on input from sensor data. This scenario can also work in a lead/lag operation or duty cycle
scenario, by running a single Liebert CRV to match the load with the secondary unit in standby. Two or
more Liebert CRVs can be networked together for teamwork, lead/lag or cascade operation.
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Dual-Row Redundancy
Dual-row redundancy can be achieved in a similar manner to a single row redundancy plan. In this
scenario, two single rows are facing one another, sharing a cold aisle. Liebert CRV units may be networked
together to provide shared informed coverage of the row equipment demands. Redundancy can be
accomplished by locating Liebert CRVs at the ends of the rows and directing their airflow inward towards
the equipment row, as shown. Operating all four Liebert CRV units at partial load or two units at full load
with two in standby is recommended for unit redundancy. Furthermore, it is suggested that when utilizing
this configuration, Liebert CRVs at opposite ends of the rows should be in operation, to deliver the most
effective coverage to the equipment. Aligning two Liebert CRVs across the row from one another is an
acceptable design, assuming that each Liebert CRV will be operating at partial capacity or operating
together at full capacity only in an emergency situation.
NOTE: Equipment loads that require a greater amount of cooling can utilize additional Liebert CRVs
located in-between the row of equipment. The discharge of the in-between Liebert CRVs should be
directed both to the left and right, adding supplemental cooling to the effect of the Liebert CRVs
located at the end of the row.
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Scenario 4: Partial Containment
The Liebert CRV is most effective when the cold aisle can be contained by a natural or manufactured
obstruction opposite to the face of the unit. As can be seen in this layout, a single Liebert CRV is
positioned at the end of a rack row that is parallel to a room wall. The wall opposing the row equipment
acts as a containment barrier supporting pressurization of the cold aisle. Additionally, the end of the
equipment row being located on a room wall acts as an end panel preventing wraparound of cool mixing
with the hot aisle air. In conjunction with this effect, the Liebert CRV discharge is positioned to provide a
curtain of cooling that encapsulates the cold aisle, acting as an end cap to the cold aisle.
NOTE: To achieve a level of redundancy in this scenario, it is suggested to locate an additional Liebert
CRV in one of two locations. Locate an additional operating Liebert CRV at the end of the equipment
row adjacent to the wall (to the far left in the illustration above). The two units will operate at a reduced
capacity each, while still providing the required cooling. Should a failure of a unit occur, the remaining
Liebert CRV unit will be able to provide cooling and airflow requirements from an acceptable position.
Alternatively, locate a standby, non-operating Liebert CRV adjacent to the operating Liebert CRV. This
allows for the same basic positioning of the unit while maintaining the intent of this scenario.
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Scenario 5: Cold-Aisle Containment
The Liebert CRV is ideal for use with a cold-aisle containment approach, with the Liebert Cold Aisle
Containment solution or similar products. Utilizing the Liebert CRV in conjunction with cold-aisle
containment products does not limit the location of the Liebert CRV with respect to the rack row. The
Liebert CRV can be located anywhere within the equipment row, with the unit’s discharge air baffle
directed as the equipment airflow needs demand. The cold aisle containment completely encapsulates
the available cooling in the aisle maximizing cooling efficiency while preventing hot air intrusion through,
around or over the row of equipment.
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omissions. Specifications are subject to change without notice.
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