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7 - WaTER CONNECTIONs
ATTENTION: Before carrying out any water connections
install the water box purge plugs (one plug per water box
in the lower section - supplied in the control box).
For size and position of the heat exchanger 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, fouling and deteriora-
tion of the pump fittings. Consult either a water treatment
specialist or appropriate literature on the subject.
7.1 - Operating precautions
The water circuit should be designed to have the least num-
ber of elbows and horizontal pipe runs at different levels.
Below the main points to be checked for the connection:
•
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(s).
•
Use an expansion device to maintain pressure in the
circuit(s) and install a safety valve as well as an expan-
sion 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 all pipework, after testing for leaks, both to
reduce heat gains and to prevent condensation.
•
Cover the insulation with a vapour barrier.
•
Where there are particles in the fluid that could foul
the heat exchanger, a screen filter should be installed
ahead of the pump. 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 (e.g.
no reversal between evaporator and condenser).
•
Do not introduce any significant static or dynamic pres-
sure 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 recommen-
ded 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.
26
Carrier recommendations on heat exchange fluids:
1.
No NH
ammonium ions in the water, they are very
4+
detrimental for copper. This is one of the most impor-
tant factors for the operating life of copper piping. A
content of several tenths of mg/l will badly corrode the
copper over time.
2.
Cl
Chloride ions are detrimental for copper with a risk
-
of perforations by corrosion by puncture. If possible
keep below 10 mg/l.
3.
SO
sulphate ions can cause perforating corrosion, if
2-
4
their content is above 30 mg/l.
4.
No fluoride ions (<0.1 mg/l).
5.
No Fe
and Fe
ions with non negligible levels of dis-
2+
3+
solved 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 < 1 mg/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 oxy-
genation conditions must be avoided. It is as detrimen-
tal 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.
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