- 52 -
External chilled
(warm) water pump
Compressor
(Preparation)
20 sec.
15 sec. min
(Note 1)
(Start)
(Stop)
(Stop)
(Start)
15 sec. min
(Note 2)
(3) Group control over external pumps
When pump group control is selected, the heat pump and the external chilled (warm) water pump are
grouped together. As shown below, the external pump starts at least 15 seconds before the compressor
and continues running for at least 15 seconds after the compressor has stopped.
Note 1. The preceding operation of the external pump is automatically prolonged (to up to 180 seconds; field adjustable) until a water
flow to a module stabilizes.
Note 2. The time that the external pump continues running after the compressor has stopped depends on the low-pressure states of
each circuit. (up to 180 seconds; field adjustable)
To protect water from freezing, the external pump not only continues running for some time after the heat
pump is stopped, but also is activated automatically while the heat pump is off according to the water
and evaporation temperatures.
4. Single-module operation
The unit module mode is available to allow you check high-pressure switch during a test run or for use as an
emergency backup in the event of a failure of the module controller.
In this mode, the module is activated when the entering water temperature exceeds the capacity control enable
threshold and deactivated when it drops below the capacity control disable threshold.
Unless any other module is running in Remote Group mode, the internal pump operates at a frequency that results in a
preprogrammed flow rate. If there are any modules running in Remote Group mode, the internal pump operates at
variable speeds according to the average of the operation frequencies of the other modules.
Note: The unit controller determines the number of compressors to run (out of the four compressors) and
their operation frequencies in order to make the leaving water temperature close to the setpoint.
Temperature when
capacity control
starts
Temperature when
capacity control
ends
Set water
temperature
Inlet water
temperature
Differential
(for start)
Differential
(for end)
Temperature [°C]
During cooling operation
Outlet water
temperature
Capacity control
range
(Note)
Time
When you use the pump group control, ensure that water is present in the pipe to protect the pump
before you start it. Exercise care so that the water circuits must not be isolated by the solenoid
valve, etc.
Note
