Hitachi YUTAKI M-Serie Bedienungsanleitung Seite 23

DRAIN PIPING
8.2.4 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 unit is equipped with an air purger (factory supplied)
at the highest location of the 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,
• Additionally, in cases where water drainage is difficult, an
anti freeze mixture of glycol (ethylene or propylene) should
be used (content between 10% to 40%). The performance
of the unit working with glycol may decrease in proportion to
the percentage of glycol used, since the density of glycol is
higher than that of the water.
• 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 (6 litres/minute for 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 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.
- 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.
13 PMML0342B rev.1 - 03/2016
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"Optional functions" chapter).
- 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.
• When necessary, put insulation on the pipes in order to
avoid heat losses.
• Whenever possible, sluice valves should be installed for
water piping, in order to minimize flow resistance and to
maintain sufficient water flow.
• 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.