This cooling system is designed to evacuate 120 kW from the racks of electronics in the counting rooms of COMPASS.
The unit is a closed liquid circuit working according to the LCS2 principle and connected to a primary circuit through an heat exchanger. A small Programmable Logical Controller controls the operation.

• The primary circuit is the SPS chilled water circuit supplying temperature of 6°C inlet and 12°C outlet.

• The secondary is a closed liquid circuit connected to the water/air exchangers installed in the racks. A circulator pump moves the fluid from a pressurized storage tank to the exchangers through a brazed plates heat exchanger connected to the primary circuit via an electrical 3 ways valve.

• Vacuum pump : KNF N026ANE - max. flow : 20 [l/mn] - min.pressure : 100 [mbar.a]
• Vacuum switch: HUBA 625.64301121 - Range -50/-600 [mbar]

• GRUNDFOS CRNE32-1-1 - Flow max : 15 [m3/h] at head max 150[m].
• Pressure sensor: HUBA 691.904207183 - -1/+3 [bar] - Ouput 4-20[mA].

• Temperature controller : CAL 9900 - PID autotuning - LCD display - Output 0-10 [V] - Alarm ouput
• 3 ways valve: SAUTER B6R40F310 - DN40 - kvs 16 [m3/h] - exponential characteristic - Servomotor AVR32W32s - 2-10 [V].
• Heat exchanger: SWEP B35 X 80 AISI 316 brased plates - Designed for 120 [kW] with 6/12 and 14/20 °C.

• SIEMENS LOGO! 24[V] - 1 terminal LCD display - 12 digital inputs - 8 output relay.

• 1 manometer on the control box for the vacuum in the storage tank.
• 1 manometer at the outlet of the pump.
• 1 manifold in the false floor equiped with manometers on inlet and outlet.
• 1 show glass on each return line before the main manifold.
• Liquid temperature displayed by the controller on the control box.
• Visual liquid level in the tank.

• Switch float level on the tank.
• High pressure switch on the tank.
• Auto-protection on the circulating pump.
• Protection on the vacuum pump.

• High temperature on the temperature controller
• Circulator OFF
• Vacuum pump ON: it give the possibility to record the pumping time and their frequency, therefore the evolution of the leaks with the time for the whole system.

• Relief valve on the storage tank – 1mbara.

The liquid is held in the storage tank below atmospheric and this pressure is controlled by the vacuum pump via a pressure switch.

A second switch fixs a maximum pressure point to stop the circulator (case of main leak).

The whole system is stopped and needs to be resetted if the vacuum pump works for more than 20 minutes.

If the pressure value is contained between the operating setting point and the upper point (switching difference) the circulator and the temperature regulation (controller and valve) run. The vacuum pump and the electrovalve are off. This is the running mode.

If the pressure goes higher than the upper point of the vacuum switch the vacuum pump starts,the 3 ways electrovalve is actuated after 2 sec. and the pressure goes down to the lowest setting point pressure (the minimum admissible pressure). The circulator and the temperature regulation are still running.

A manual vaccum pump switch lets the operator to active it in order to gas out the circuit or to fill the storage tank with fluid (3 positions switch on PPV).

The outlet pressure of the circulator is controlled by a pressure sensor via the PID 3 phase frequency converter. The set point can be adjusted by a manual potentiometer (Pump setpoint).

The alarm will flash if:

• The pressure in the storage tank is too high.
• the water level in the storage tank is not correct.
• The vacuum pumps has worked more than 20mn.

• Switch on the main power (I) on the control box.
• Switch the 3 positions switch on ON; the vacuum pump starts; the circulator will start after the pressure in the tank reachs [700mbar.a]. If starting from the atmospheric pressure it will take about 30 [mn].
• The pumping time of the vacuum pump is limited to 20 [mn]. If it stops and the fault lamp flashs press the RESET button.
• Adjust the outlet pressure of the circulator with the potentiometer PUMP SETPOINT.
• To adjust the set point on the temperature controller press and hold * to display the set point and pressñ or ò to increase or decrease.
• To stop the circulation switch the 3 positions switch on PPV; the system stays under pressure control and the 3 ways valve is closed.
• To stop the system switch the 3 positions switch on STOP; the pressure will rise to the atmospheric one depending of the leak rate of the system. One can break the vacuum with the switch valve PURGE on the control box.

• Heat exchangers: 32 connected in the racks.
• Demineralized water: 350 [l] filled in the storage tank.
• Lower pressure point in the storage tank: 700 [mbar.a].
• Upper pressure point in the storage tank: 750 [mbar.a].
• Vacuum pumping speed: 5 [mn] for 50 [mbar].
• Alarm pressure point in the storage tank: 800 [mbar.a].
• Outlet pressure of the pump: 1200 [mbar.a].
• Pressure in the inlet manifolds (in the false floor): 950 [mbar.a].
• Pressure in the return manifolds (in the false floor): 600 [mbar.a].
• Flow through one heat exchanger in the racks: 460 [l/h].
• Temperature setting point: 16 [°C]