Hitachi YUTAKI M RASM-2VRE Instruction Manual page 24

DRAIN PIPING
• 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
6 litres/minute, 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.
- 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 safety valve and the air purger are properly
driven or oriented 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.
12 PMML0506 rev.1 - 09/2019
9.2.5 Water filling
1 Check that a water check valve (ATW-WCV-01 accessory)
with a shut-off valve (field supplied) is connected to the
water filling point (water inlet connection) for filling the space
heating hydraulic circuit (see
2 Make sure all the valves are open (water inlet/outlet shut-off
valves and the rest of valves of the space heating installation
components).
3 Ensure that the air purgers of the unit and installation work
correctly.
4 Connect a drain pipe to the safety valve and make sure that
it is correctly connected to the general draining system. The
safety valve is later used as an air purging device during the
water filling procedure.
5 Fill the space heating circuit with water until the pressure
displayed on the manometer reaches approximately 1.8 bar.
?
N O T E
While the system is being filled with water, it is highly recommended
to operate the safety valve manually so as to help with the air purging
procedure.
6 Remove as much air from inside the water circuit as possible
through the air purger and other air vents in the installation
(fan coils, radiators...).
7 Start the air purge procedure test. There are two modes
(Manual or Automatic) which helps in case of installations
with heating and DHW operation:
a. Manual: Start and stop the unit manually using the unit
controller (Run/Stop button) and also using the DSW4
pin 2 of the PCB1 (ON: Forced to derive to DHW coil;
OFF: Forced to derive to space heating).
b. Automatic: Select the air purge function using the user
controller. When the automatic air purge function is
running, the pump speed and the position of the 3-way
valve (space heating or DHW) are automatically changed:
Water
pump
ON
DHW
3Wv
OFF
8 If a little quantity of air is still remaining in the water circuit,
it should be removed by the manual air purger of the unit
during the first hours of operation. Once the air in the
installation has been removed, a reduction of water pressure
in the circuit is very likely to occur. Therefore, additional
water should be filled until water pressure returns to an
approximate level of 1.8 bar.
"9.2 Space heating and DHW").
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