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3.6 Calculation of water system holdings
Unit Type
CA0065EANR
The effective water capacity of the water system during operation includes the total capacity of the water
system, such as the main water pipe, the water storage tank, and the normally open end of the two-way
valve.
The actual effective capacity V of the water system during operation must be greater than or equal to
Vmin, otherwise the unit will frequently alarm and stop!
◆ Water system volume calculation example
Assume that two CA0065EANR module units are installed in a water system, and the return water
temperature is set to 12 degrees. The main pipe diameter is DN65. The total length of the inlet and outlet
pipes is 80m. Eight of the end wind disks remain normally open. The internal volume is 2L.
Calculation: inlet and outlet water volume = 3.14*{(65/2)/1000}2*80*103=265L
End wind disk water capacity = 10 * 2 = 20L
According to the above table can be found. Minimum capacity required by the water system Vmin.=310L
In order to avoid frequent shutdown and alarm of the unit, the capacity of the water tank must be greater
than or equal to Vmin.=310-265-20=25L
3.7 Expansion tank volume calculation
The air conditioning water system must be installed with a certain volume of expansion water tank to
adapt to the change of system water volume caused by water temperature changes (thermal expansion
and contraction), to prevent the freezing of winter water system and the instability of pump suction
pressure; at the same time, as system hydration and exhaust use.
Volume calculation of the expansion tank:
V_p=α*△t*V_S
V_p----The effective volume of the expansion tank (the volume of water from the height difference
between the signal tube and the overflow tube), m3
α----The volume expansion coefficient of water, α=0.0006/°C
△t----Maximum water temperature change value, °C
V_S----Water flow in the system (including the sum of water in the pipeline and equipment in the system),
m3
3.8 Circulating pump selection principle
Circulating pump water flow ≥ unit rated water flow × 1.1
Closed circulating water system: circulating pump head ≥ (water system along the path resistance +
water system local resistance + unit water pressure drop) × 1.1
Open circulating water system: circulating pump head ≥ (water system hydrostatic pressure + water
system local resistance + water system resistance + unit water pressure drop) × 1.1
When multiple units are equipped with a pump, the circuit with the highest resistance is generally the
farthest unit circuit.
Set the return water temperature
12
WARNING
18
Minimum effective water
capacity Vmin.(I)
310
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