20
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 deterioration 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 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(s).
-
Use a pressure reducer to maintain pressure in the circuit(s)
and install a relief valve as well as 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 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, or directly at the exchanger inlet in case the pump is
more than 20m away. The mesh size of the filter must be 1.2
mm.
-
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).
-
Before any start-up verify that the heat exchange fluid is
compatible with the materials and the water circuit coating.
-
The use of different metals on hydraulic piping could generate
eletrolytic pairs and consequently corrosion. Verify then, the
need to install sacrificial anodes.
In case additives or other fluids than those recommended by the
manufacturer are used, ensure that the fluids are not considered
as a gas, and that they belong to class 2, as defined in directive
2014/68/UE.
The manufacturer 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.
-
Cl
-
Chloride ions are detrimental for copper with a risk of
perforations by corrosion by puncture. If possible keep 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 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 and 2.5 can
be 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: Any sudden change in water oxygenation
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.
-
Electric conductivity 10-600µS/cm.
-
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.
Summary of Contents for 19PV550
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