New VRVIII heat recovery
Daikin Europe N.V. (18/11/2007)
Our VRVIII heat recovery system combines the renouned VRVIII heat pump/cooling only models with the more recent mini VRVIII-S and replaces the earlier VRVII heat recovery system.
The new VRVIII system however, whilst incorporating the best features of its VRVII predecessor, represents a significant step forward in addressing both existing and forthcoming environmental regulations and in addition to its heat recovery facility, also offers consultants, contractors, service engineers and end users many design, installation and maintenance friendly refinements.
Many new features
Among its most important new features is the ability to connect up to 64 indoor units (40 for VRVII) to a single outdoor unit in increments of 2HP up to 48HP. Outdoor unit modules can be configured on a combined ‘multi’ basis between 18 and 48HP with a single heat exchanger as well as in ‘stand alone’ format from 8 to 16HP with two heat exchangers that is currently the largest single unit on the market. VRVIII HR also offers up to 200% overall increase in unit diversity ratio for a single outdoor module system and 160 to 130% on double or triple multi modules. Operating range is wide at -5°C to 43°C in cooling and -20°C to 15.5°C in heating and the system supports no less than 14 different format indoor fan coil units, including the new and much acclaimed 360° radial airflow ‘Roundflow’ ceiling cassette.
Unlike contemporary VRF systems, which cease operating during defrost and oil return, alternate defrosting of the heat exchangers on VRVIII HR multi module outdoor units or the dual outdoor coil of single modules allows continuous heating to be supplied from the indoor units throughout these cycles thereby avoiding the transmission of cold draughts of air into the room area.
Leakage prevention is ensured by the use of brazed joints in place of flanged and flared connections before the shut off valves as well as by brazed pressure sensors and electronic gauges instead of sensors and gauge ports. There is also on average, 10% less refrigerant charge compared to a similar VRVII system.
A new design BSVQ branch selector box enables the cooling/heating changeover function to be activated by pressure equalisation at the box itself rather than for the entire system. In this way the 13 minute maximum ‘no capacity’ status of VRVII during changeover, which is in any case reduced to a maximum 8 minutes on VRVIII HR, occurs only on the unit changing over and not on other units in the same condensing system.
Also important is the ‘night quiet’ mode, which can be set automatically to cut in 8 hours after peak daytime temperature and run for 10 hours before reverting to normal operating mode. During the night quiet mode, 10 hour cycle, operating sound can go down to 45dBA. Alternatively, starting and ending times can be input manually via a time clock or both automatic and manual modes can be combined as required.
Design flexibility is also enhanced by the incorporation of a powerful new inverter driven outdoor unit fan, which provides a higher ESP of 78.4Pa (58.8Pa for VRVII). Outdoor unit
footprint is less than similar capacity VRVII models and piping lengths are the highest in the industry at 1000m (total system), 165m (maximum run), 90m (maximum level difference) and 90m (longest branch).
In the event of a malfunction automatic back up is provided on outdoor models, enabling a twin compressor single module to operate on a single compressor until the fault is rectified and continuous operation for 8 hours on for example, two out of three multi modules, after the remote controller has been reset.
Automatic charging and checking
Daikin’s well known strict adherence to imminent ‘F’ Gas regulations are reflected in the unique VRVIII capacity for refrigerant containment during both charging and system operation. This important facility enables the amount of additional refrigerant charging during commissioning to be controlled automatically. Charging, initiated via a button on the outdoor unit printed circuit, ceases as soon as the correct amount of refrigerant is transferred. Refrigerant cylinder ‘empty’ status is indicated on the remote controller. An electronic containment check can also be activated manually, any changes being indicated by LEDs on the outdoor unit PCB.
Meeting legislative requirements
VRVIII HR takes full account of all legislative efficiency requirements by returning an enviable 14% average increase in efficiency and 20% increase in single unit efficiency over VRVII HR. COPS and EERs of up to 4.4 and 4.2 respectively are obtained at 100% connection. Efficiency improvements of this order stem from the application of new technology, which results in a 3 – 10% increase in airflow rates from the new aero spiral high output dual DC fan and grille assembly and low pressure loss bellmouth. Also, a new 3 wall heat exchanger increases effective coil surface. Friction losses are also reduced by virtue of its high thrust mechanism, which reduces operating noise as well as generating improved efficiency.
