Requirements And Recommendations For The Hydraulic Circuit; Water Flow Control - Hitachi YUTAKI RWM-2R1E Installation & Operation Manual

REFRIGERANT AND WATER PIPING

6.5.4 Requirements and recommendations for the hydraulic circuit

• The maximum piping length depends on the maximum pressure availability in the water outlet pipe. Please check the pump
curves.
• The indoor unit is equipped with an air purger (factory supplied) at the highest location of the Indoor Unit. If this location is not the
highest of the water installation, air might be trapped inside the water pipes, which could cause system malfunction. In that case
additional air purgers (field supplied) should be installed to ensure no air enters the water circuit.
• For heating floor system, the air should be purged by means of an external pump and an open circuit to avoid air bags.
• When the unit is stopped during shut-off periods and the ambient temperature is very low, the water inside the pipes and the
circulating pump may freeze, thus damaging the pipes and the water pump. In these cases, the installer shall ensure that the
water temperature inside the pipes does not fall below the freezing point. In order to prevent this, the unit has a self-protection
mechanism which should be activated (refer to the Service manual,
• Check that the water pump of the space heating circuit works within the pump operating range and that the water flow is over the
pump's minimum. If the water flow is below 12 litres/minute for 4.0-10.0HP unit (6 litres/minute for 2.0/2.5/3.0HP unit),alarm is
displayed on the unit.
• An additional special water filter is highly recommended to be installed on the space heating (field installation), in order to
remove possible particles remaining from brazing which cannot be removed by the indoor unit water strainer.
• When selecting a tank for DHW operation, take into consideration the following points:
The storage capacity of the tank has to meet with the daily consumption in order to avoid stagnation of water.
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- Fresh water must circulate inside the DHW tank water circuit at least one time per day during the first days after the
installation has been performed. Additionally, flush the system with fresh water when there is no consumption of DHW during
long periods of time.
- Try to avoid long runs of water piping between the tank and the DHW installation in order to decrease possible temperature
losses.
- lf the domestic cold water entry pressure is higher than the equipment's design pressure (6 bar), a pressure reducer must be
fitted with a nominal value of 7 bar.
• Ensure that the installation complies with applicable legislation in terms of piping connection and materials, hygienic measures,
testing and the possible required use of some specific components like thermostatic mixing valves, Differential pressure overflow
valve, etc.
• The maximum water pressure is 3 bar (nominal opening pressure of the safety valve). Provide adequate reduction pressure
device in the water circuit to ensure that the maximum pressure is NOT exceeded.
• Ensure that the drain pipes connected to the safety valve and to the air purger are properly driven to avoid water being in contact
with unit components.
• Make sure that all field supplied components installed in the piping circuit can withstand the water pressure and the water
temperature range in which the unit can operate.
• YUTAKI units are conceived for exclusive use in a closed water circuit.
• The internal air pressure of the expansion vessel tank will be adapted to the water volume of the final installation (factory
supplied with 0.1 MPa of internal air pressure).
• Do not add any type of glycol to the water circuit.
• Drain taps must be provided at all low points of the installation to permit complete drainage of the circuit during servicing.

6.5.5 Water flow control

YUTAKI pumps can estimate the water flow by electronic calculation. Therefore, there is no need to install a water flow switch with
the new YUTAKI pumps.
However, if a secondary pump is installed or glycol is used (in the case of YUTAKI M), it is necessary to install a water flow control,
as the electronic calculation may be affected.
61 PMML0575 rev.2 - 03/2022
"Optional functions" chapter).