15
Installation
■
Calculations of Water System Inventory
CAUTION
During unit operation, the actual operating capacity of the water system is less than the minimum water
capacity required, resulting in frequent alarm and shutdown of the unit.
Model of unit
Preset return water temperature (
℃
) Minimum effective water capacity Vmin. (I)
CA0035EAND
12
155
CA0070EAND
12
310
CA0100EAND
12
620
CAUTION
The effective water capacity of the running water system includes the total capacity of the water main,
water tank, 2-way valve normally-open end which are involved in water circulation in the water system.
The actual effective water capacity (V) of the running water system must be more than or equal to Vmin.,
otherwise the unit may be subject to frequent alarm or shutdown!
Calculation example of water system capacity
Assume that one wr system is paterovided with two sets of CA0070EAND units, and the preset return
water temperature is 12
℃
. The diameter of water main is DN65, and the total length of water inlet &
outlet pipelines is 80m. Eight end fan coils are normally open. The internal capacity is 2L.
Calculations:
Capacity of inlet & outlet water mains = 3.14 X {(65/2)/1000}
2
X 80 X 10
3
= 265L
Water capacity of end fan coil = 10 X 2 = 20L
The above table indicates that the required minimum capacity of the water system Vmin.=310L
To avoid frequent startup, shutdown and alarm of the unit, the capacity of water tank must be more than
or equal to Vmin.=310-265-20=25L
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Type Selection of Auxiliary Electric Heater
According to engineering requirements, it is recommended that one set of auxiliary electric heater be
used as standby system, which is started to keep water temperature of the unit in case of defrosting or
temporary fault of such equipment.
Considerations on type selection of auxiliary electric heater mainly include the minimum average outdoor
ambient temperature in winter and the capacity of standby system. Based upon the local minimum
average ambient temperature in winter and the water outlet temperature of the unit, the unit capacity
attenuation Q2 can be obtained via comparison between the capacity Q1 from the "Performance
Correction Curves" and the nominal capacity Q of the unit.
Q2 = Q - Q1
The capacity of auxiliary electric heater generally selected, W
W = a* Q2 = a*(Q - Q1)
。
In which, a refers to margin coefficient, taking between 1.0 and 1.5, and it is larger in northern area, e.g.
taking 1.5 in Hubei province and its northern area.
CAUTION
In heating mode, the unit capacity may drop with the decreasing ambient temperature, thus users shall
add the auxiliary electric heater at the hot water side for the areas under the low average outdoor
ambient temperature in winter, otherwise the unit performance may be affected.
CA0130EAND
465
12
