Safety Devices (Fig. 5) - Arneg MPM 2 Manuel D'installation Et De Service

The control unit is provided with a display that makes it possible to control all the operational and safety
parameters for the unit.
In the case of electronic malfunction, a back-up pressure switch system is available as an OPTION, that
allows the unit to continue operation until technical assistance arrives.
Instructions for programming the electronic unit can be found in the manual for installation and use of the
electronic control device.

16.Safety devices (Fig. 5)

A cartridge pressure switch with fixed calibration of 28 bar with manual reset is installed on each compressor
on the discharge.
MPM2 units are provided with a pressure switch panel, including high and low pressure safety switches and
high and low pressure transducers necessary for adjustment.
Pressure Switches Panel (Rif. 6)
1 - General LOW pressure switch
2 - General HIGH pressure switch (SRMCR) (Calibration ARNEG:Ps=25.2bar)
3 - Low pressure transducer
4 - High pressure transducer
Operation of back-up pressure switch (Rif. 7):
The system begins to operate at the moment in which, due to malfunction of the electronic unit, the
compressors are turned off leading to an increase of the low pressure. When the value of this pressure
exceeds the limits set for the number "5" pressure switch for more than 20 minutes (default setting on the
delay device located inside the control panel), all the output relays on the electronic board are disabled,
causing switchover to electromechanical operation.
A red "EMERGENCY OPERATION" indicator light is located on the control panel, which will light up to
indicate the intervention of the back-up system. Using a relay (with no power on its contacts) located on the
control panel, it is possible to transmit this alarm at a distance.
Hence, compressors are turned on and/or turned off based on the calibration values of the pressure switches
identified by the numbers 6, 7, 8, and 9 (in the case of 4-compressor units) or by the pressure switches with
the numbers 6, 7, and 8 (in the case of 3-compressor units).
Calibration parameters:
- Field of adjustment:
- Differential
- Reset
- Contacts action
The calibration parameters found in the tables below are calculated taking into account:
- Pressure switch no. 6, compressor I
- Pressure switch no. 7, compressor II
- Pressure switch no. 8, compressor III (if present)
- Pressure switch no. 9, compressor IV (if present)
Pressure
Compressor
switch
No.
6
7
8
9
Pressure
Compressor
switch
No.
6
7
8
9
In order to avoid overloading the electric line, delay times are set by default as follows:
- Pressure switch no. 5 delay for switch over to stand-by = 30 minutes
- Pressure switch no. 6 delay for start up of compressor no. I after switch over = 30 mn.
05060107 00 03/02/2010
T.N. Units
Stop
No. bar
I 2,1
II 2,3
III 2,5
IV 2,7
B.T. Units
Stop
No. bar
I 0.3
II 0.4
III 0.5
IV 0.6
MPM2 - Medium Power Multisystem
Adjustable -0.2 → 7.0 bar
Adjustable 0.7 → 4.0 bar
Automatic
SPDT
Start Diff.
bar Bar Stop °C
2,8 0,7 -19
3,0 0,7 -18
3,2 0,7 -16
3,4 0,7 -14
Start Diff.
bar Bar Stop °C
1.0 0,7 -40
1.1 0,7 -39
1.2 0,7 -38
1.3 0,7 -37
R404A
Start °C
-13
-12
-11
-9
R404A
Stop °C
-30
-29
-27
-26
English
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