35VERTIV™ - Liebert
®
EFC - UM - 10040805MAN_ENG - 30.03.2023
Unit operation is completely automatic. The below sequence
explains how unit operates:
• The data center air, pushed in by the fans, enters the unit.
•
passes through the heat exchanger.
•
of delivery air and relays this information to the con trol system.
The control system compares this temperature with the unit
set point and, as a function of that, the EC fans speed is
modulated to reach the unit set point.
exchanger side, does not permit the heat transfer from data
center air, the evaporative system and/or the backup cooling
it enters the unit.
• The treated and cooled data center air is then dispersed in the
data center.
• The outdoor air, after it absorbs heat from the data center air
through the heat exchanger is dispersed in the atmosphere.
The unit is not designed to provide humidity
If the outdoor air condition is favorable, the unit works on air-to-air
cooling mode (Dry mode): the outdoor air absorbs heat from the
data center air.
heat exchanger can generate a vertical temperature gradient on
the air supplied to the data center by the EFC unit.
When this occurs, the temperature setpoint is still ensured as it is
measured considering the average between the readings of three
temperature probes positioned respectively at the top, center and
bottom of the data center delivery section of the EFC.
If the air is not mixed in the adjacent ductwork, or there is no plenum
that provides an air mixing, the gradient could be maintained. This
mixing system in the ductwork after the EFC units.
In dry mode, in case the outdoor temperature is below 10°C, the
deviation from the average value can be up to 7K; this value is
primary and secondary sides.
When the outdoor air is too hot and the air-to-air exchange is not
enough, the evaporative system is turned on and the outdoor
air is cooled down. A conductivity sensor keeps under control
the recirculated water conductivity: when the water conductivity
exceeds the maximum admitted value, the water is discharged and
new water is supplied to the unit.
The water discharge is controlled by a motorized ball valve,
normally opened, with spring return; water feed is controlled a
motorized ball valve, that it is normally closed and with spring return.
The correct water level is kept on the drain panel by two level
switches (min level or max level reading).
The unit control discharges the water when there is risk of water
freezing, when the water level is too high on the drain panel or
when there is risk of scaling and when the unit shut down.
Due to the chemical and thermo-mechanical
characteristics of the composite heat exchanger, it is expected that,
after the initial start-up, a conditioning period is required in order to
reach the nominal performances of the unit in evaporative cooling
mode.
During this period no actions are required and the unit can work
in evaporative cooling mode without any restriction, but the
performance provided by the unit could result slightly lower than
the one reported in the rating software datasheet. This occurrence
startup of the unit.
Data sheets from the rating software report the unit performance
after a running-in period of hours in wet mode, even if it is
expected it increases furthermore.
In extreme outdoor conditions, when there is the need of partial or
full backup, the digital scroll compressor (with modulating capacity)
thus cooling the air passing over it.
Check oil level inside compressor after min. of compressor
running at maximum capacity: oil level must be between 1/2 and
3/4 of sight glass. In tandem compressors the oil level must be
checked with both compressors running at maximum capacity
(note: when only one compressor is running, the oil level inside the
compressor that is not currently running could be at the minimum
and the compressor, that is running, at the maximum capacity;
when one compressor is running at maximum capacity and one
compressor is running in modulating capacity, the oil level in the
latter one could be between 1/2 and the minimum).
In extreme outdoor conditions, when there is the need of partial
or full backup, the control system opens the valve which permits
the cold water to enter the coil, thus cooling the air passing over it.
All maintenance operations must be strictly carried out by observing
the European and National accident prevention regulations.
We refer especially to the accident prevention regulations
concerning electrical systems, refrigerators, and manufacturing
resources.
Maintenance may be done to air conditioning equipment only by
In order to keep all warranties valid, the maintenance must adhere
to the manufacturer’s regulations.
: The work must be done in the system only
when it is at standstill. Do this by switching the air
conditioner at the controller and the main switch. Post a
warning sign saying: “”.
Electrical components of device have to be switched and be
checked that they are .
Ignoring the safety instructions can be dangerous to people as well
as to the environment.
Soiled parts always cause a loss of performance while switches or
control devices can lead to the break-down of a plant.
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