DIGI
All apartments should be fitted with a Heat Interface Unit (HIU). Each HIU should take its primary heat source from a district heating system, and must be capable of exchanging heat via direct connection to the apartment heating system and indirect connection to the Domestic Hot Water.
The HIU should be fitted with a double wall plate heat exchanger to minimise any cross contamination water paths in a plate perforation situation. The plate heat exchanger should be sized to fulfil the hot water loads of the property up to 26 l/min at 10-55°C. It should be possible for hot water temperature to be pre-set on the unit during commissioning, however all temperature controls should be inaccessible to the occupant.
The DHW mode should be activated by a flow turbine at 0.6 l/min, and the HIU should have a primary boost function to accelerate the primary flow to the plate heat exchanger, enabling the HIU to achieve DHW setpoint stability within 60 seconds from cold.
Each HIU should be fitted with an EPP casing to reduce heat loss. The casing should be fitted with tamper-proof security screws to restrict access to internal components. Overall dimensions of the HIU must not exceed 570mm Wide x 390mm High x 170mm Deep.
Each HIU should be fitted with an ultrasonic energy meter. The energy meter should enable wired connection to an M-Bus network but also have 3 pulse inputs to make possible the connection of additional hot and cold water meters and an electricity meter. The energy meter must be accessible to the occupant without the need to remove the HIU casing. The heat meter must also be powered by the M-Bus network with battery back-up should the M-Bus network fail.
Each HIU shall include the following features:-
- Commissioning settings accessible locally via a laptop or handheld device.
- Self learning and adjusting to fluctuations in primary system pressure.
- Option for remote connectivity for data logging, fault finding, and adjustment of operating parameters.
- Stepper Motor control over both the heating and hot water circuits with full primary closure within 5 seconds of tap closure.
- DHW Set-point between 45°C and 60°C.
- Return temperature limitation.
- DHW plate heat exchanger, Anti-legionella cycle every 24 hours.
- Intelligent Domestic Hot Water pre-heat function with the ability to turn the pre-heat off after 1 hour of inactivity and the ability to set the pre-heat temperature independently of the DHW temperature.
- Differential pressure control valve across the Heating circuit primaries.
- Pre-plumbing bracket with isolation valves and option for flushing bypass and underfloor heating interface.
- Qp1.5 Heat Meter with M-Bus output and 3 Pulse Inputs
Heating Performance
- Maximum - 21kW at 70-40°C
Hot Water Performance
- Minimum - 1 ltr / Min
- Maximum - 81kW - 26 ltr / Min @ 10-55°C (based on 80°C Primary flow temperature)