Mitsubishi Electric PUHY-P250YJM-A Data Book page 48

Example-3 Combination of closed type cooling tower and boiler
T1 : Proportional type, insertion system thermostat
T2 : Proportional type, insertion system thermostat
T3 : Proportional type, insertion system thermostat
V1 : Proportional type, motor-driven 3-way valve
S : Selector switch
R : Relay
XS : Auxiliary switch (Duplex switch type)
Pump interlock
In the summer, as the circulation water temperature rises exceeding the set temperature of T1, the bypass port of V1
will close to lower the circulation water temperature. In the winter, if the circulation water temperature drops below
25°C[77°F], V2 will conduct water temperature control to keep the circulation water temperature constant.
During the stopping of the heat source water pump, the bypass port of V2 will be closed fully by interlocking.
The start/stop control of the fan and pump of the closed type cooling tower is applied with the step control following
the command of the auxiliary switch XS of V1, thus controlling water temperature and saving motor power.
Heat
source
unit
Heat source
water pump
R
- 39 -
Closed type
cooling tower
XS
V1
T1
Boiler
V2
T2
Relay board