Ductable air-cooled scroll
chillers and heat pumps
17
Concentration
%
0
10
20
30
40
50
Mono-ethylene glycol (MEG)
ºC
0
-3
-7
-13 -20 -29
Mono-propylene glycol (MPEG) ºC
0
-2
-5
-10 -15 -21
-25
-30
-15
-20
-5
-10
0
20
40
50
10
30
-45
-35
-40
0
3
4
1
2
Temperature °C
Volume concentration %
Warning
: the glycol concentration must keep the
fl
uid at least 6°C
below the outlet water temperature foreseen in the evaporator in order
to allow a correct adjustment of the evaporator's minimum pressure
regulation. If the concentration is below the necessary amount, there
is a risk of freezing. On the other hand, any excess of concentration
entails a decrease in performance.
Required glycol concentration
Note: The values are offered as a guide according to the standard
characteristics of the MEG. These may vary based on the MEG
manufacturer, which is why it is necessary to consult the manufacturer
data in order to guarantee protection up to the desired temperature.
Minimum freezing and usage temperature graphs
Minimum usage temperature:
- Mono-propylene glycol
- Mono-ethylene glycol
Freezing temperature:
- Mono-propylene glycol
- Mono-ethylene glycol
Corrosion behaviour
* Max. 60ºC
+ Good resistance under normal conditions.
0 There may be corrosion problems, especially if other factors intervene.
- Not advisable.
Note:
For open-circuit installations, if it is not possible to
maintain the water conditions within the values indicated
in the previous table, it will be necessary to install an
exchanger that separates the unit's circuit from the water
circuit to be treated by using materials compatible with these
characteristics, whether stainless steel or titanium.
The units' hydraulic circuits are made of copper pipes. The exchanger
plates are made of AISI-316 stainless steel, and the material used for
soldering the plates is copper.
The following table indicates corrosion behaviour for copper and the
AISI-316 stainless steel with regard to water with different compositions.
Values outside these ranges can cause corrosion problems in the
hydraulic circuit and in particular in the plate exchangers.
It is recommended that the water
fi
lling the hydraulic circuits be
fi
ltered
and treated, if necessary.
Water content
Concentration (mg/l)
AISI 316
Copper
Organic substances
+
0
Electrical
conductivity
< 500
μ
S/cm
+
+
> 500
μ
S/cm
+
-
NH
3
< 2
+
+
2 - 20
+
0
> 20
+
-
Chlorides *
< 300
+
+
> 300
0
+
Sulphites, chloride-free
< 5
0
+
> 5
0/-
0
Iron in solution
< 10
+
+
> 10
+
0
Free carbonic
acid
< 20
+
0
20 - 50
+
-
50
+
-
Manganese in
solution
< 1
+
+
> 1
+
0
pH value
< 6
0
+
6 - 9
0/+
+
> 9
+
0
Oxygen
< 2
+
+
> 2
+
+
Sulphates
< 70
+
+
70 - 300
+
0
> 300
-
-
- Check the pH obtained with pH paper strips or a pH metre.
- Place a label in a visible place that indicates:
* the presence of anti-freeze in the installation,
* the name of the product and the supplier,
* the dosage and the pH as of the time the unit is started up.
If more amount is needed, it must be exactly the same mixture as
the product initially used.
The following table and curves feature the minimum glycol percentages
required for the installation in accordance with the freezing point.
The pumps that incorporate the 30PAC/PHC units can work with any
concentration of mono-ethylene glycol, albeit with a reduction in the
available pressure due to the variation of water
fl
ow. The pump must
be changed for mono-propylene glycol (upon request).
Summary of Contents for 30PA
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