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19 - BRINE OPTION (OPTION 5B & OPTION 6B)
This option allows production of brine down to 0°C (option 5B) /
-15°C (option 6B). The unit is equipped with suction pipe insulation
(option 6B only) and a fan frequency converter.
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).
Example: For operation with ethylene glycol at 45% and a brine
temperature of -15°C (entering temperature -10°C), the maximum
outside operating temperature will be around 33°C.
Operating range with 45% ethylene glycol
55
45
35
25
15
5
-5
-15
-25
-20
-15
Evaporator leaving water temperature, °C
Option 5B
Option 6B
19.1 - Frost protection
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.
This value will allow the definition of the following limits:
1. Evaporator frost protection
2. Low pressure protection
It is recommended that the commissioning of a brine system is
done by Carrier.
For information: The protection values given by our supplier, based
on the antifreeze solutions used in the Carrier Montluel laboratory,
are as follows: (these values can change for different suppliers).
52
-10
-5
0
5
10
% by weight,
Freeze point, °C
glycol
ethylene glycol
10
15
20
25
30
35
40
45
Based on the table above, if the ethylene glycol concentration by
weight in the water loop is 35% the value of -19.1°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.
Minimum frost protection temperature
0
-5
-10
-15
-20
-25
-30
-16
-14
-12
-10
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
(options 116) is 45%.
• The temperature of -15°C brine can only be obtained
with ethylene glycol at 45%.
• 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:
• every 40 000 hours for applications with water,
• every 15 000 hours for applications with glycol
concentrations above 30%.
To facilitate maintenance operations, it is recommended to
install shut-off valves upstream and downstream of the unit.
Freeze point, °C
propylene glycol
-3.8
-2.6
-6.1
-4.3
-8.8
-6.6
-11.8
-9.6
-15.2
-13
-19.1
-16.7
-23.6
-20.7
-29
-25.3
-8
-6
-4
-2
0
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