Instruction Manual for Hitachi DHWT Domestic Hot Water Tank

Quick guide from the manual

This manual provides installation and operation instructions for the Hitachi DHWT-200S-3.0H2E and DHWT-300S-3.0H2E domestic hot water tanks. These units are designed to be used with external heat sources such as heat pumps (e.g., YUTAKI S, YUTAKI S80, or YUTAKI M). Key installation steps include ensuring the unit is installed upright on a level surface, connecting the hydraulic circuits, and performing electrical wiring according to the provided diagrams.

Safety Precautions

DANGER: Do not connect the power supply to the indoor unit and DHW tank before filling both circuits with water and checking for leaks. Do not pour water over electrical parts. In case of fire, turn off the main switch and contact your service contractor.

CAUTION: Do not use flammable sprays (insecticide, lacquer, hair spray) within one meter of the system. Maintenance must be performed by qualified personnel. Ensure children do not play with the appliance.

Installation

The DHWT unit must be installed in an indoor location with sufficient clearance for operation and maintenance. The unit must be installed vertically on a flat, even surface capable of supporting its full weight when filled with water. Use the built-in adjustable feet to ensure the unit is level. The unit must be securely fastened to the wall.

Hydraulic Circuit

When performing piping connections:

• Connect pipes as close to the unit as possible to facilitate future disconnection.
• Use flexible joints for water inlet and outlet to prevent vibration transmission.
• Install sluice valves to minimize flow resistance.
• Install ball valves on both water pipe connections to simplify maintenance.
• Ensure the system is fully air-purged before operation to prevent damage to heating elements.
• Apply thermal insulation to hydraulic pipes to prevent heat loss and accidental burns.

Electrical Wiring

Electrical connections must be performed by a professional installer. Ensure the power supply voltage is within +/- 10% of the rated voltage. The earth wire must be securely connected. Use a fuse of the specified capacity. Ensure all terminal block screws are tightly fastened.

Maintenance

To replace the thermostat or heating element:

1. Turn off the power supply and water supply, then drain the unit.
2. Remove the electric central cover.
3. Unscrew the wires from the thermostat and element.
4. Remove the thermostat by pulling it straight out.
5. Use an element tool to remove/replace the heating element, ensuring the O-ring seal is in place and undamaged.
6. Fill the unit with water and check for leaks before reconnecting power.
7. Tighten all wire connections and re-tighten after 3 months.

Troubleshooting

If the system does not operate, check the YUTAKI set temperature, electrical connections (fuse/circuit breaker), water temperature/thermostat cut-out, and water pressure (min 0.1 MPa). If the unit is not heating well, check for water flow obstructions and ensure water pressure is within the operating range.

Technical Specifications

The DHWT-200S-3.0H2E has a capacity of 194L, while the DHWT-300S-3.0H2E has a capacity of 284L. Both units operate on 1~ 230V 50Hz power. The safety valve for the secondary circuit should be set to 7 bar, and the primary circuit safety valve to 3 bar.