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8.1.2 - Carrier recommendations on heat exchange fluids
The water supply must be analysed and appropriate filtering,
treatment and control devices built in to suit the application and
prevent corrosion, fouling and deterioration of the pump
fittings.
Consult either a water treatment specialist or appropriate
literature on the subject.
1. No NH
4+
ammonium ions in the water, they are very
detrimental for copper. This is one of the most important
factors for the operating life of copper piping. A content of
several tenths of mg/l will badly corrode the copper over
time. If required, use sacrificial anodes.
2. Cl
-
Chloride ions are also detrimental for copper with a
risk of perforations by corrosion by puncture. If possible
keep at a level below 10 mg/l.
3. SO
4
2-
sulphate ions can cause perforating corrosion, if
their content is above 30 mg/l.
4. No fluoride ions (<0.1 mg/l).
5. No Fe
2+
and Fe
3+
ions with non negligible levels of
dissolved oxygen must be present. Dissolved iron < 5 mg/l
with dissolved oxygen < 5 mg/l.
6. Dissolved silicon: silicon is an acid element of water and
can also lead to corrosion risks. Content < 1mg/l.
7. Water hardness: TH >5 °F. Values between 10 and 25 can
be recommended. This will facilitate scale deposit that can
limit corrosion of copper. TH values that are too high can
cause piping blockage over time. A total alkalimetric titre
(TAC) below 100 is desirable.
8. Dissolved oxygen: Any sudden change in water oxygena-
tion conditions must be avoided. It is as detrimental to
deoxygenate the water by mixing it with inert gas as it is
to over-oxygenate it by mixing it with pure oxygen. The
disturbance of the oxygenation conditions encourages
destabilisation of copper hydroxides and enlargement of
particles.
9. Specific resistance – electric conductivity: the higher the
specific resistance, the slower the corrosion tendency.
Values above 3000 Ohm/cm are desirable. A neutral
environment favours maximum specific resistance values.
For electric conductivity values in the order of 200-6000
S/cm can be recommended.
10. ph: Ideal case ph neutral at 20-25°C
7 < ph < 8
-
If the water circuit must be emptied for longer than
one month, the complete circuit must be placed under
nitrogen charge to avoid any risk of corrosion by
differential aeration.
-
Charging and removing heat exchange fluids should
be done with devices that must be included on the
water circuit by the installer. Never use the unit heat
exchangers to add heat exchange fluid.
8 - WaTER CONNECTIONs
For diameters and position of the heat exchanger water inlet
and outlet connections refer to the certified dimensional
drawings supplied with the unit.
The piping must not in any way lead to mechanical constraints
on the heat exchangers.
8.1 - Operating precautions
8.1.1 - general
The fluid to be cooled (often water) must meet the criteria
below.
The hydraulic circuit must be equipped with filters, purges,
vents and unit shut-off valves.
The essential points to verify are:
•
Comply with the water inlet and outlet connections shown
on the unit.
•
Install manual or automatic air purge valves at all high
points in the circuit.
•
Use an expansion device to maintain pressure in the
circuit.
•
Install a safety valve as well as an expansion tank
(included with the hydronic module option).
•
Install thermometers in both the entering and leaving
water connections (recommendation).
•
Install drain connections at all low points to allow the
whole circuit to be drained.
•
Install stop valves, close to the entering and leaving water
connections.
•
Use flexible connections to reduce the transmission of
vibrations.
•
Insulate all pipework, after testing for leaks to prevent
condensation.
•
A screen filter must be installed in the water circuit
(included with the hydronic module option). The mesh
size of the filter must be 1.2 mm (see ‘Typical water
circuit’ diagram on the right).
•
Before the system start-up verify that the water circuits are
connected to the appropriate heat exchangers.
•
Do not introduce any significant static or dynamic
pressure into the heat exchange circuit (with regard to the
design operating pressures).
•
Before any start-up verify that the heat exchange fluid is
compatible with the materials and the water circuit
coating.
•
In case additives or other fluids than those recommended
by Carrier are used, ensure that the fluids are not considered
as a gas, and that they belong to class 2, as defined in
directive 97/23/EC.
