34
8.6.4 Minimum water flow
The minimum chilled water flow is shown in the table 8-13. If the
system flow is less than the minimum unit flow rate, the evaporator
flow can be recirculated, as shown in the diagram.
Recirculation
UNIT
Fig. 8-32 For minimun water flow rate
8.6.5 Maximum water flow
The maximum chilled water flow is limited by the permitted pressure
drop in the evaporator. It is provided in the table 8-13. If the system
flow is more than the maximum unit flow rate, bypass the evaporator
as shown in the diagram to obtain a lower evaporator flow rate.
Recirculation
UNIT
Fig. 8-33 For maximum water flow
8.6.6 Minimum and Maximum water flow
Table 8-13 (unit: m
3
/h)
Item
Model
Water flow rate
Minimum
Maximum
KEM-30 DNS3
3.8
6.4
KEM-60 DNS3
8.0
13.0
KEM-90 DNS3
10.2
16.5
8.6.7 Selection and installation of the pump
8.6.7.1 Select the pump
a. Select the water-flow of the pump
The rated water-flow must no less than the unit rated water-flow; in
terms of multi-connect the units, that water-flow must no less than
total units’ rated water-flow.
b. Select the lift of the pump.
H=h1+h2+h3+h4
H: The lift of the pump.
h1: Main unit water resistance.
h2: Pump water resistance.
h3: Water resistance of the longest water-loop distance, includes:
pipe resistance, different valve’s resistance, flexible pipe resistance,
pipe elbow and three-way resistance, two-way resistance or three-
way resistance, as well as filter resistance.
H4: the longest terminal resistance.
8.6.7.2 Installation the pump
a. The pump should be installed at the water inlet pipe, both of which
sides must mount the soft connectors for vibration-proof.
b. The backup pump for the system (recommended).
c. Units must with a main unit controls (Please see Fig. 8-22 for the
controls wiring diagram).
8.6.8 Water quality control
8.6.8.1 Water quality control
When industrial water is used as chilled water, little furring may
occur; however, well water or river water, used as chilled water, may
cause much sediment, such as furring, sand, and so on. Therefore,
well water or river water must be filtered and softened in softening
water equipment before flowing into chilled water system. If sand
and clay settle in the evaporator, circulation of chilled water may be
blocked, and thus leading to freezing accidents; if hardness of chilled
water is too high, furring may occur easily, and the devices may be
corroded. Therefore, the quality of chilled water should be analyzed
before being used, such as PH value, conductivity, concentration of
chloride ion, concentration of sulfide ion, and so on.
8.6.8.2 Applicable standard of water quality for the unit
Table 8-14
PH value
6.8-8.0
Total hardness
<70ppm
Conductivity
<200μV/cm (25°C)
Sulfide ion
No
Chloride ion
<50ppm
Ammonia ion
No
Sulfate
<50ppm
Silicon
<30ppm
Iron content
<0.3ppm
Sodium ion
No requirement
Calcium ion
<50ppm
Содержание KEM-30 DNS3
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