Water Connections; Operating Precautions - Carrier AquaSnap 61WG Series Installation, Operation And Maintenance Instructions

9 - WATER CONNECTIONS

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.

9.1 - Operating precautions

Design the water circuit with the least number of elbows and
horizontal pipe runs at different levels. The main points to be
checked for the connection are:
- The use of different metals on hydraulic piping could generate
eletrolytic pairs and consequently corrosion. Verify then, the
need to install sacrificial anodes.
- 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 expan-sion tank. Units
with hydraulic module and option 293 or 293A include the
relief valve and expansion tank.
- 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 vibration transmission.
- If the insulation provided is not sufficient, insulate the cold-
water piping, after testing for leaks, both to reduce heat loss
and to prevent condensation.
- Cover the insulation with a vapour barrier.
- If the external water piping to the unit is in an area where the
ambient temperature can fall below 0 °C, insulate the piping
and install an electric heater on the piping.
NOTE: For units without option 293 or 293A, a screen filter
must be installed as close as possible to the heat exchanger
and in a position that is easily accessible for removal and
cleaning. Units with a hydraulic module include this filter.
The mesh size of the filter must be 1.2 mm. If this filter is not
installed, the plate heat exchanger can quickly become
contaminated at the first start-up, as it takes on the filter
function, and correct unit operation is affected (reduced water
flow due to increased pressure drop).
Damage due to absence of relief valve, expansion tank or
screen filter (i.e. without option 293 or 293A) is not covered
by the warranty.
ATTENTION: Use of units in an open loop is forbidden.
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.
If 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.
Recommendations on heat exchange fluids:
- No NH ammonium ions in the water, they are very
4+
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
(the plate heat exchangers used for these units have brazed
copper joints).
- Cl Chloride ions are detrimental for copper with a risk of
-
perforations by corrosion by puncture. If possible keep below
125 mg/l.
- SO 2- sulphate ions can cause perforating corrosion, if their
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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 silica: silica is an acid element of water and can
also lead to corrosion risks. Content < 1mg/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 is desirable.
- Dissolved oxygen: Any sudden change in water oxygena-tion
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.
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.
9.2 - Water connections
The diagram below illustrates a typical hydraulic installation. When
the hydraulic circuit is charged, use the air vents to evacuate any
residual air pockets.
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