Hitachi YUTAKI M RASM-3WF2E Installation And Operation Manual page 34

◆ Additional DHW Circuit recommendation
In places where possible hard water areas, to prevent and minims scale situations, it is
recommended to reduce stored water temperature to a maximum of 131 °F (55 °C), as huge scale
quantity could damage the water tank and the electrical heater.
Flush the domestic water circuit with at least 10 times its volume of water. The life of the water
tank will be shorter if groundwater (spring water, well water, etc..) is used without treatment which
can lead to the corrosion of the tank. The water must not be aggressive or encrusting at any time.
The result of calculating the Langelier Index should be between +/- 0.5.
In installation locations where the result of Langelier Index calculation are out of the expected
value with a tendency to corrosive water, it is recommended to install the active anode accessory).
In the regions where the water is very hard (or out of requirements values) or where the result
of Langelier Index calculation are out of expected value with a tendency to hard water, it is
recommended fitting a softener system. Please ensure that softener system will be capable of
providing effective protection against corrosion. It is recommended to install the active anode
accessory.
As DHW Tank water is being used for storing drinking water, this water has to be in accordance
with national regulations and Hitachi's quality minimum requirements. The use of softeners, active
anodes or other protective systems will not bring a derogation from Hitachi's provided warranty.
5.4 Minimum water volume description
5
The following part shows how to calculate the minimum water volume in the system for product
protection (anti-hunting) and temperature drop at defrosting.
MODEL 3 RT 4 RT
Minimum Volume * gal (L) 14.5 (55) 14.5 (55)

NOTE
(*) Minimum volume is applicable for usual working conditions. If T temperature during normal
wi
operation is below 77 °F (25 °C), the following steps must be applied to consider the defrost effect.
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PMEN0657 rev.0 - 02/2024