26
HYDRAULIC CONNECTIONS
Water component for corrosion limit
Precautions for the Winter
The water could freeze and damage the exchanger of the unit and other parts of the system during the winter period, if the system
was to remain at a standstill. This problem can be obviated in 3 different ways:
1 .
Drain the system completely, taking care to drain the plate exchanger (in order to drain the unit’s piping system completely, open
the water drain ball valves and the air vent valves, open any valves closed).
2 .
Operate with glycol water taking account, depending on the % of glycol, of the factor of correction of the refrigerating capacity,
power input, water flow rate and losses of head (see table on following page)
3 .
If it is certain that the unit will always be powered throughout the winter, the unit is able to protect itself from freezing, down to a
temperature of -20°C: this is possible thanks to an antifreeze electric heating element installed on the plate exchanger and intelligent
control of the water pump that must be governed by the microprocessor board (see the “Electric Connections” section).
If the unit is fitted with a Storage tank, solution no. 3 requires installing the tank antifreeze heating element accessor.
pH
7.5 ÷ 9.0
-
SO4 --
< 100
ppm
HCO3 -/ SO4 --
>1.0
Total hardness
8.0 ÷ 15.2
°F
Cl-
< 50
ppm
PO4 3-
< 2.0
ppm
NH3
< 0.5
ppm
Air vent and water drain
On the plumbing circuit feeding the unit, the installer must fit an appropriate number of valves (manual or automatic) at the top of the
circuit in order to vent any air in the plumbing system. In the same way, he must install a water drain valve in order, when necessary,
to drain the unit’s plate exchanger completely (especially during the winter in order to prevent freezing that would seriously jeopardize
the operation of the unit).
Free Chlorine
< 0.5
ppm
Fe3+
< 0.5
ppm
Mn++
< 0.05
ppm
CO2
< 50
ppm
H2S
< 50
ppb
Temperature
< 65
°C
Oxygen content
< 0.1
ppm
To avoid corrosion problems in water exchangers make sure that the water used in the plant meets the requirements listed in the table.
Expansion vessel volume (liters)
10
Safety valve set (bar)
3
Thermal expansion of water (10-40°C)
0.0074
Thermal expansion of water (10-60°C)
0.0167
H (metri)
Expansion vessel
pressure (bar)
IR
IP
Case A
H <0
1
667
299
Case B
0 < H < 17
1
667
299
12
1,5
500
225
15
1,8
400
180
20
2,3
233
105
Maximum volume of water in the system with wet module
Before filling the water system, it is advisable to consider the type of installation in question, i.e. check the difference in level between the wet
module and user. The following table gives the maximum water content of the water supply system in liters, depending on the capacity of the
standard expansion vessel supplied and the pressure at which it should be charged. The expansion vessel setting must be regulated to suit
the maximum positive difference in level of the user.
Maximum setting value 600 kPa.
With a positive H of more than 12.25 meters, calculate the expansion vessel precharge value in kPa using the formula below:
Expansion vessel precharge= [H/10 .2+0 .3] x100 = [kPa]
NOTE. In case A, make sure that the user’s lowest point is able to withstand the global pressure.
Tab.1
NOTE:
If the unit operates with brine, calculate the real volume of the system by taking into account the corrective factors for the volume of
the system given in the table below.
Corrective factors per total maximum volume of the system with brine
% of brine
0%
10%
20%
30%
40%
Cooling Mode
1,000
0,738
0,693
0,652
0,615
Heating Mode
1,000
0,855
0,811
0,769
0,731
U
CASE B
CASE A
U= User
U
D
1453
202
E
288
220
53
614
576
150
1038
60
53
167
131
215