Mitsubishi Electric PLFY-WP VBM-E, Data Book

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3. SYSTEM DESIGN GUIDE
WR2
MEE15K052
5) Practical System Examples and Circulation Water Control
Example-1 Combination of closed type cooling tower and hot water heat storage tank (using underground hollow slab)
Since the water heat source HYBRID CITY MULTI is of water heat source system, versatile systems can be consti-
tuted by combining it with various heat sources.
The practical system examples are given below.
Either cooling or heating operation can be performed if the circulation water temperature of the water heat source
HYBRID CITY MULTI stays within a range of 15~45°C [59~113°F]. However, the circulation water temperature near
32°C [90°F] for cooling and 20°C [68°F] for heating is recommended by taking the life, power consumption and
capacity of the air conditioning units into consideration. The detail of the control is also shown below.
By detecting the circulation water temperature of the water heat source HYBRID CITY MULTI system with T1 (around
32°C [90°F]) and T2 (around 20°C [68°F]), the temperature will be controlled by opening/closing V1 in the summer
and V2 in the winter.
In the summer, as the circulation water temperature rises exceeding the set temperature of T1, the bypass port of V1
will open to lower the circulation water temperature. While in the winter, as the circulation water temperature drops,
V2 will open following the command of T2 to rise the circulation water temperature.
The water inside the heat storage tank will be heated by the auxiliary heat source by V3 being opened with timer
operation in the night-time. The electric heater of the auxiliary heat source will be controlled by T3 and the timer.
The start/stop control of the fan and pump of the closed type cooling tower is applied with the step control of the fan
and pump following the command of the auxiliary switch XS of V1, that operates only the fan at the light load while the
fan and pump at the maximum load thus controlling water temperature and saving motor power.
Heat
source
unit
Heat exchanger
Heat storage
tank pump
T1~T4 : Thermostat
V1~V2 : Proportional type
motor-driven 3-way valve
V3 : Motor-driven 3-way valve
XS : Auxiliary switch
MG : Magnetic switch
EH : Electric heater
Heat storage tank
Auxiliary
heat source
T2
V2
EH
T4
MG
V3
T3
Cooling water pump
Closed type
cooling tower
Expansion tank
Circulation
water pump
V1
T1
XS
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