23
After the unit has been commissioned, the power supply
must only be disconnected for quick maintenance operations
(one day maximum). For longer maintenance operations or
when the unit is taken out of service and stored (e.g. during
the winter or if the unit does not need to generate cooling)
the power supply must be maintained to ensure supply to
the compressor oil crankcase heaters.
For dimensions and position of the water inlet and outlet
connections refer to the certified dimensional drawings
supplied with the unit. The water pipes must not transmit any
radial or axial force to the heat exchangers nor any vibration.
The water supply must be analysed and appropriate filtering,
treatment, control devices, isolation and bleed valves and
circuits built in, to prevent corrosion (example: tube surface
protection damage in case of impurities in the fluid), fouling
and deterioration of the pump fittings.
Before any start-up verify that the heat exchange fluid is
compatible with the materials and the water circuit coating.
Where additives or other fluids than those recommended by
Carrier are used, ensure that these are not considered as a gas,
and that they are class 2, as defined in directive 97/23/EC.
Carrier recommendations on heat exchange fluids:
• 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.
• Cl
-
Chloride ions are also detrimental for copper with
a risk of perforations by corrosion by puncture. Keep
at a level below 10 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 with non negligible levels of
dissolved oxygen must be 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 1.0 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. It is as detrimental to deoxyge-
nate the water by mixing it with inert gas as it is to over-
oxygenate it by mixing it with pure oxygen. The distur-
bance of oxygenation conditions encourages destabilisa-
tion of copper hydroxides and enlargement of particles.
• Specific resistance – electric conductivity: the higher the
specific resistance, the slower the corrosion tendency.
Values above 30 Ω·m are desirable. A neutral
environment favours maximum specific resistance
values. For electric conductivity values in the order of
20-60 mS/m can be recommended.
• pH: Ideal case pH neutral at 20-25°C (7 < pH < 8)
ATTENTION: Filling, completing and draining the water
circuit charge must be done by qualified personnel, using the
air purges and materials that are suitable for the products.
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.
Before the system start-up verify that the water circuits are
connected to the appropriate heat exchangers. The water
circuit should be designed to have the least number of
elbows and horizontal pipe runs at different levels. Below
the main points to be checked for the connection:
• Observe 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 a pressure reducer to maintain pressure in the
circuit(s) and install a safety valve as well as an expan-
sion tank. Units with the hydronic module include a
safety valve and an expansion tank.
• Install thermometers in both the entering and leaving
water connections.
• 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 the pipework, after testing for leaks, to prevent
heat transmission and condensation.
• Cover the insulation with a vapour barrier. If the water
piping outside the unit passes through an area where
the ambient temperature is likely to fall below 0°C, it
must be protected against frost (defrost solution or
electric heaters).
NOTE: A screen filter must be installed in units without
hydronic module. This must be installed in the water inlet
piping upstream of the pressure gauge and close to the
unit heat exchanger. It must be located in a position that
is easily accessible for removal and cleaning. The mesh
size of the filter must be 1.2 mm.
If the filter is missing, the plate heat exchanger or the
shell-and-tube evaporator can quickly become fouled during
the first start-up, as it will perform the filter function, and
correct unit operation will be affected (reduced water flow
rate due to the increased pressure drop).
Units with hydronic module include this type of filter.
• Do not introduce any significant static or dynamic
pressure into the heat exchange circuit (with regard to
the design operating pressures).
• Any products that may be added during the water
connection stage to provide thermal insulation of the
containers must be chemically neutral towards the
materials and coatings on which they are placed. All
original materials supplied by Carrier comply with
this requirement.
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