16
9 - WATER CONNECTIONS
For size and position of the unit water inlet and outlet connec-
tions 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, shutoff and bleed valves and circuits
built in, to prevent corrosion (example: damage to the protection
of the tube surface if the fluid is polluted), fouling and deter-
ioration of the pump fittings.
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 s.a 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.
Carrier s.a. recommendations on heat exchange fluids:
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.
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
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 >2.8 K. 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 oxygen-
ation 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).
ATTENTION: Charging, adding or draining fluid from the
water circuit must be done by qualified personnel, using air
vents and materials suitable for the products. The water
circuit charging devices are field-supplied.
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.
9.1 - Operating precautions and recommendations
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:
•
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
system and install a safety valve as well as an expansion
tank.
Units with a hydronic module include the safety valve and
the 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 all pipework, after testing for leaks, both to
reduce thermal leaks and to prevent condensation.
•
If the external unit water pipes are in an area, where the
ambient temperature is likely to fall below 0°C, insulate the
piping and add an electric heater. The internal unit piping
is protected down to -20°C.
NOTE: For units not equipped with a hydronic module a
screen filter must be installed as close to the heat exchanger
as possible, in a position that is easily accessible for removal
and cleaning. Units with hydronic module are equipped with
this type of filter.
The mesh size of the filter must be 1.2 mm.
The plate heat exchanger can foul up quickly at the initial
unit start-up, as it complements the filter function, and the
unit operation will be impaired (reduced water flow rate due
to increased pressure drop).
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 pressure
into the heat exchange circuit (with regard to the design
operating pressures).
The products that may be added for thermal insulation of the
containers during the water piping connection procedure
must be chemically neutral in relation to the materials and
coatings to which they are applied. This is also the case for
the products originally supplied by Carrier s.a.
