Unit Protection Devices, Operating Limits And Operating Range - CIAT EREBA ACCESS T 017 Manual De Instrucciones

11 - UNIT PROTECTION DEVICES, OPERATING LIMITS AND OPERATING RANGE

The water content is necessary to ensure the stability of plant operation
and accurate temperature control.
It is often necessary to add a buffer water tank to the circuit in order to
achieve the required volume.
NOTE:
For industrial process cooling applications, where high stability of
water temperature levels must be achieved, the values above must
be increased.
We recommend consulting the factory for these particular
applications.
Brine operation
For EREBA ACCESS HT units, it is possible to produce brine down to 0°C.
For EREBA ACCESS T units, it is possible to produce brine down to -8°C.
The unit is equipped with suction pipe insulation.
The operating range is a function of the suction pressure, which in turn
is a function of:
- the brine type,
- the brine concentration,
- the flow rate,
- the brine temperature,
- the condensing pressure (ambient temperature).
The evaporator low pressure and frost protection depends on the amount
of antifreeze added to the water circuit. The evaporator approach (LWT -
SST) as well as frost protection are based on this amount.
It is therefore essential to control the amount of antifreeze in the
water loop at the first start-up (circulate for 30 minutes to ensure
good homogeneity of the mixture before taking the sample). Refer to
the manufacturer's data to define the frost protection, based on the
concentration rate measured.
The frost protection temperature must be used in the unit software
parameters.
It is recommended that the commissioning of a brine system is done
by manufacturer.
For information: The protection values given by our supplier, based on
the antifreeze solutions used in our laboratory, are as follows: (these
values can change for different suppliers).
% by weight, glycol
10
15
20
25
30
Based on the table above, if the ethylene glycol concentration by weight
in the water loop is 30% the value of -15.2°C must be used in the software.
It is essential to carry out an annual check (minimum) of the amount of
glycol, and adjust the frost protection value in the software based on the
rate measured. This procedure must be systematic, if water or antifreeze
solution is added.
The curve below shows the minimum frost protection temperature that
must be observed, based on the leaving water temperature.
Freeze point, °C ethylene glycol
-3,8
-6,1
-8,8
-11,8
-15,2
EN - 17
Minimum frost protec on temperature
0
-2
-4
-6
-8
-10
-12
-14
-16
-18
-20
-9 -7 -5 -3
Evaporator leaving water temperature, °C
NOTES:
• For unit frost protection at low air temperature, the brine percentage
must be evaluated.
• The maximum glycol rate for units with hydraulic kit is 30 %.
• The maximum recommended temperature difference is 5 K.
IMPORTANT: For glycol concentrations below 20% a corrosion inhibitor
suitable for the application must be used to avoid corrosion due to the
agressive nature of brine.
The presence of glycol reduces the life of the pump fittings.
It is recommended to change the fittings or the pump regularly.
To facilitate maintenance operations, it is recommended to install
shut-off valves upstream and downstream of the unit.
Maximum water content of hydraulic circuit
The units provided with hydraulic module are supplied with an expansion
vessel (in option) to limit the water content of the hydraulic circuit. The
table below shows the maximum content of water and a mix of water/
ethylene glycol of the hydraulic circuit.
EREBA ACCESS
017 - 021
T/HT
Static pressure bar 1.5
L
Water 200
L
GE 10% 150
L
GE 20% 110
L
GE 30% 90
GE: ethylene glycol
-1 1 3 5
026 - 040
3 1.5 3
50 350 140
38 263 105
28 193 77
23 158 63
EREBA ACCESS 17 - 40 T/HT
EN