24
7.2 - Water connections
The diagrams on the following page illustrate a typical
hydronic installation. When the hydronic circuit is filled, use
the air vents to evacuate any residual air pockets.
7.3 - Frost protection
The units are designed to be installed under cover at outside
temperatures b5°C and +40°C. Therefore they do not
include anti-freeze protection, as standard.
If the water piping is in an area where the ambient tempera-ture
can fall below 0°C it is recommended to install a trace heater
on the piping and to add an antifreeze solution to protect the
unit and the water piping to a temperature of 10 K below the
lowest temperature likely to be reached at the installation site.
Use only antifreeze solutions, approved for heat exchanger
duty. If the system is not protected by an antifreeze solution and
will not be used during the freezing weather conditions,
draining of the cooler and outdoor piping is mandatory.
Damage due to freezing is not covered by the warranty.
IMPORTANT: Depending on the climatic conditions in your
area you must:
•
Add ethylene glycol with an adequate concentration to
protect the installation up to a temperature of 10 K below
the lowest temperature likely to occur at the installation
site.
•
If the unit is not used for an extended period, it is
recommended to drain it, and as a safety precaution add
ethylene glycol to the heat exchanger, using the heat
exchanger water entering purge valve connection.
•
At the start of the next season, refill the unit with water
and add an inhibitor.
•
For the installation of auxiliary equipment, the installer
must comply with basic regulations, especially for
minimum and maximum flow rates, which must be
between the values listed in the operating limit table
(application data).
•
To avoid corrosion by differential aeration, the complete
heat exchange circuit must be charged with nitrogen, if
it is drained for longer than one month. If the heat
exchange fluid does not comply with Danfoss
recommendations, the circuit must immediately be filled
with nitrogen.
7.4 - Flow switch (units without hydronic module)
IMPORTANT: On BW10 units, the unit water flow switch
must be energised, and the chilled water pump interlock must
be connected. Failure to follow this instruc-tion will void the
Danfoss guarantee.
The flow switch is supplied, installed on the evaporator leaving
water pipe and preset at the factory to cut out when there is
insufficient water flow.
Terminals 34 and 35 are provided for field installation of the
chilled water pump interlock (auxiliary contact for pump
operation to be wired on site).
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
Danfoss 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.
Danfoss 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 con-tent
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 10 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
dis-solved 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 < 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.
•
Specific resistance – electric conductivity: the higher the
specific resistance, the slower the corrosion tendency.
Values above 30 Ohm·m are desirable. A neutral
environment favours maximum specific resistance values.
For electric conductivity values in the order of 20-60
mS/m can be recommended.
•
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.
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