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7 - WATER CONNECTIONS
When connecting units to the water distribution pipe work, refer
to the certified dimensional drawings supplied with the unit for
the dimensions and position of the water inlet and outlet
connections.
The pipes and tubes should not transmit any axial or radial forces
to the exchangers or any vibrations.
The water must be analysed and the circuit must include
provision of any necessary water treatment: filters, additives,
intermediate exchangers, bleed valves, vents, shut-off valves, etc.
depending on the results, in order to prevent corrosion (e.g.
damage to the surface of the tubes due to impurities in the fluid),
fouling and deterioration of the pump lining.
Before any start-up, check that the heat transfer fluid is
compatible with the hydraulic circuit materials. Where additives
or other fluids than those recommended by Carrier are used,
ensure that these are not considered gases, and that they are
class 2, as defined in directive 2014/68/EU.
Carrier's recommendations concerning heat transfer fluids:
•
No NH
4
+
ammonium ions in the water - these are very harmful
to 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.
•
Cl
-
Chloride ions are also harmful to copper with a risk of
perforating corrosion. Keep at a level below 125 mg/l.
•
SO
4
2-
sulphate ions can cause perforating corrosion if their
content is above 30 mg/l.
•
No fluoride ions (<0.1 mg/l).
•
No Fe
2+
and Fe
3+
ions if non-negligible levels of dissolved
oxygen are present. Dissolved iron < 5 mg/l with dissolved
oxygen < 5 mg/l.
•
Dissolved silicon: Silicon is an acid element of water and
can also lead to corrosion risks. Content < 1 mg/l.
•
Water hardness: >0.5 mmol/l. Values between 1 and 2.5
mmol/l are recommended. This will facilitate scale deposit
that can limit corrosion of copper. Values that are too high
can cause piping blockage over time. A total alkalimetric
titre (TAC) below 100 mg/l is desirable.
•
Dissolved oxygen: Avoid any sudden change in water
oxygenation conditions. Deoxygenating the water by mixing
it with inert gas and over-oxygenating it by mixing it with
pure oxygen are both equally harmful. The disturbance of
oxygenation conditions encourages destabilisation of copper
hydroxides and precipitation of particles.
•
Electric conductivity 10-600 µS/cm.
•
pH: Ideal case pH neutral at 20-25°C (7.5 < pH < 9).
CAUTION: Filling, topping up or emptying the water circuit
must be carried out by qualified personnel using tools and
equipment suitable for the products. The heat transfer fluid
should be filled using devices fitted to the hydraulic circuit by
the installer.
7.1 - Operating precautions and recommendations
Before any system start-up, verify that the hydraulic circuits are
connected to the appropriate heat exchangers. The water circuit
should be designed to have the least number of elbows and and
changes in elevation; the main points to be checked for the
connection are listed below.
•
Ensure the water outlet and inlet connections match those
marked on the unit.
•
Install manual or automatic air purge valves at all high
points in the circuit.
•
Maintain the pressure of the circuit(s) with pressure
reducers and install a safety relief valve and an expansion
tank. Units supplied with a hydraulic module include a valve.
Units supplied with option 293 include an expansion tank.
•
Install thermometers in both the water inlet and outlet
pipes.
•
Install drain connections at all low points to allow the whole
circuit to be drained.
•
Install shut-off valves close to the water inlet and outlet
connections.
•
Use flexible connections to reduce the transmission of
vibrations.
•
Insulate the pipework, after testing for leaks, to prevent
heat transmission and condensation.
•
Cover the insulation with a vapour barrier. If the water
pipes outside the unit pass through an area where the
ambient temperature is likely to fall below 0°C, it must be
protected against frost (anti-freeze solution or electric
heaters).
•
The use of different metals in the hydraulic system may
create galvanic couples and lead to corrosion. Verify then
the need to install sacrificial anodes.
•
Do not introduce significant static or dynamic pressure, as
compared to the stated operating pressures, into the heat
transfer fluid circuit.
•
Products used for thermal insulation must be chemically
neutral to the surfaces on which they are applied. All
original materials supplied by Carrier comply with this
requirement.
NOTE: A screen filter must be installed for units supplied without
a hydraulic module. This must be installed on the unit's water
inlet pipe, upstream of the pressure differential gauge and close
to the unit heat exchanger. It must be located somewhere easily
accessible to enable disassembly and cleaning. The mesh size of
the filter must be no more than 1.2 mm. If the filter is missing, the
plate heat exchanger can quickly become fouled during the first
start-up, as it will trap any debris in the system, and correct unit
operation will be affected (reduced water flow rate due to the
increased pressure drop).
Units with a hydraulic module are equipped with this type of
filter.