Toshiba RUAGP Series Original Owner's Manual page 53

3. Pump control
The unit controller adjusts the rotation speed of a pump inside each module using an inverter, as directed by the
module controller. For details, see the section "Group of modules control" (P.47).
The following sections describe other pump controls.
(1) Preceding and succeeding pump operations
When an operation command from the module controller is received, the unit controller performs a pre-operation
of the pump before starting up the compressor. The first pump starts. For the second and subsequent pumps,
start as necessary. The minimum time guard from the start of the pump till the compressor operation is 35
seconds.
When a stop command from the module controller is received, the unit controller stops the compressor then
stops the pump operation. This is performed at the average frequency of the operating pumps. For cooling
operation, the succeeding pump operation time automatically changes based on the low-pressure conditions
after the stoppage of the compressor.
<During cooling operation>
• The unit controller stops the pump if a low-pressure condition (evaporation temperature) persists at over the
freeze prevention temperature for 15 seconds or longer.
<During heating operation>
• The pump stops after completing 15 seconds of succeeding operation at the earliest.
(2) Freeze protection operation
In order to protect the water heat exchanger from freezing, the unit controller controls the starting and stopping of
the pump, based on the entering and leaving water temperature and the evaporation temperature.
* When preventing freezing, the pump runs at 150 [L/min] (minimum flow rate) per module.
<Pump operation conditions>
○ Condition 1 (when the detected evaporation temperature is higher than the freeze prevention temperature)
• Stopping: Entering/leaving water temperature < 2°C (freeze prevention temperature)
• When the thermo is off (at an operation capacity of 0%): Entering/leaving water temperature < 3°C
*1 Freeze prevention errors are not detected for 30 seconds after the pump is started for freeze prevention
purpose.
○ Condition 2 (When the detected evaporation temperature is less than the freeze prevention temperature)
• Entering/leaving water temperature < 4°C (freeze prevention temperature + 2°C)
○ Condition 3 (Intermittent operation)
• Detected evaporation temperature is < 0°C and 30 minutes have passed since pump was last stopped
*2 Evaporation temperature and stopping time can be altered according to installation conditions.
<Pump stop conditions>
○ When pump starts as result of condition 1: Entering/leaving water temperature > 5°C (freeze prevention
temperature + 3°C)
○ When pump starts as result of condition 2: Entering/leaving water temperature > 7°C (freeze prevention
*3 The default freeze prevention temperature is 2°C.
○ When pump is started under Condition 3: When pump operation time is 30 seconds or more
*4 Operating time can be altered according to installation conditions.
Note: If you are using peripheral equipment, it may be necessary to implement measures, such as using an
external signal to run the pump to prevent it from freezing if there is a large drop in temperature in
equipment other than the heat pump. For details, contact Toshiba Carrier.
(freeze prevention temperature + 1°C)
temperature +5°C)
or when the pump has continuously run for 20 minutes or more.
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