36
9 - 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.
9.1 - 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 an expansion device to maintain pressure in the circuit(s)
and install a safety 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. The mesh size of the filter must be 1.2 mm (see ‘Typical
water circuit’ diagram).
•
The use of different metals on hydraulic piping could generate
eletrolytic pairs and consequently corrosion. It could be
needed to add sacrificial anodes.
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.
In case additives or other fluids than those recommended 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.
Carrier 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
125 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 < 1 mg/l.
7. 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 is desirable.
8. 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.
9. Electric conductivity: 10-600µS/cm
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.
9.2 - Water connections
This diagram shows a typical water installation.
Typical water circuit diagram
Legend
1 Control valve
2 Air vent
3 Flow switch for the evaporator
4 Flexible connection
5 Heat exchanger
6 Pressure tap
1
2
3
4
5
6
7
8
9
10
11
12
7 Thermostat sleeve
8 Drain
9 Buffer tank
10 Filter (mesh size: 1.2 mm = 20 mesh)
11 Expansion tank
12 Fill valve
Summary of Contents for 30HXC Series
Page 49: ......
