VRV stands for Variable Refrigerant Volume or VRF Variable Refrigerant Flow and can deliver either heating or cooling at any one time. This type of system consists of a single outdoor unit connected to several outdoor units. The VRV system has a large selection of different style indoor units that can be customer selected and matched with the appropriately sized outdoor unit and are extremely flexible in design. The indoor units are all branched off a common set of refrigeration pipes. The outdoor unit increases in compressor speed depending on how many indoor units are on (as little as one) and their heat load, matching the required capacity. The refrigerant flow is controlled to each indoor unit via an electronic metering device that varies or stops the refrigerant flow through the indoor unit’s coil. All the indoor units are on a serial control loop which allows for ease of installation of a centralised controller and interfacing with a Building Management System. With this type of system one indoor unit is selected as the master indoor unit and whatever mode is selected on its controller, will dictate what modes are selectable from the slave indoor unit’s controller. These systems have primarily been installed in buildings but are becoming more common in domestic house construction due to the vast selection of indoor units to match the low set roofs of new homes today, due to the reduced over shadowing to neighbouring properties.
These systems have a large range of indoor unit styles and capacities including cassette, compact cassette, one way cassette, two-way flow cassette, ceiling suspended cassette, slim compact bulkhead, bulkhead, low static ducted, mid static ducted, high static ducted, ceiling suspended, wall mounted, floor standing, concealed floor standing, heat reclaim ventilator and heat reclaim ventilators with DX coils that can dehumidify the air as well.
VRV HEAT RECOVERY
A VRV Heat Recovery is basically the same as a VRV heat pump however the difference being that this system can provide heating and cooling simultaneously to different indoor units at the same time. There is no master controller and all indoor units’ controllers have the choice to operate in any mode. This is achieved by having a three-pipe system – liquid pipe, discharge pipe and suction pipe. From these three pipes the indoor unit can either heat or cool. The branch selection box is an additional part within the system where the three pipes enter from the outdoor unit and then two pipes exit running to the indoor unit. The branch selection box sends the required refrigerant to the indoor unit to provide either heating or cooling.
HEAT RECLAIM VENTILATOR
The heat reclaim ventilator is used to introduce outside air into a conditioned space while reducing the heat load on the system, providing heating and cooling. The Daikin HRV systems are up to 84% efficient in temperature exchange efficiency. They also exchange the enthalpy of the air being processed (transfer of moisture) and are up to 77% efficient in heating and 70% efficient in cooling. This type of system is a must in passive homes, where the air leakage of the house is very minimal, causing problems with moisture. It’s also a good option to have in any home providing air changes. The HRV draws air in from outside and exhaust air from inside. The exhausted and outside air both pass each other in the heat exchanger, and this is where the heat energy is exchanged from the outgoing and to the incoming air. The enthalpy of the air is exchanged as well. The HRV can be set up on its own controller or piggyback onto the Daikin air conditioning controller and work in conjunction with the air conditioning system. There is also an option to connect the system to a CO2 sensor that varies the amount of air required to meet the CO2 set point. There is also a bypass option that can ventilate the house and provide cooling at night when the air outside is cooler than inside. The exhausted air could be drawn from the bathroom toilets etc and delivered back into the supply air from the air conditioning system. The HRV systems are designed to be run for extended periods, providing a small amount of air flow over a long period of time. A boost option can be wired in that sets the system to full speed when the bathroom is in use, then dropping back to low speed.
