Mitsubishi Electric City Multi VRF (variable refrigerant flow) is the cutting edge in commercial air-conditioning technology – the only two-pipe simultaneous heating and cooling system in the world. Proven in the field under rigorous conditions, two-pipe technology is not only cheaper to install, but is durable, reliable, energy efficient and provides superior levels of control accuracy.
On a City Multi R2 Series VRF with four indoor unit system, there are 20 refrigerant joints, compared to an equivalent three-pipe system with 58 connections. Each extra joint requires extra labour, materials and time. Copper prices have risen significantly and less copper pipe means much less capital cost for equivalent projects. This makes City Multi R2 a significantly cheaper product to install. There are also no expensive proprietary branch fittings required. Fewer pipe connection sites also mean less potential leak sites.
Two-pipe architecture allows for quick, individual changeover of indoor units from heating to cooling. Due to the unique engineering of the BC (branch control) box, +/- 1°C of set point is possible with +/- 1.5°C dictating changeover mode.
Two-pipe architecture makes future proofing and servicing of the VRF system simpler, reducing through-life costing. Alterations and additions to individual branches are made easy by installing branch ball valves at the time of installation. This allows individual branches to be worked on while the rest of the system is still in service. All BC connections are brazed, reducing further possible leakage sites. Future additions to the system can be engineered and added while the system is still in operation.
Unlike three-pipe systems, R2 systems do not require regular oil recovery cycles. With less refrigerant volumes and velocities during mode change over, oil recovery is minimized. This prevents zone-temperature drift during recovery cycles and improves energy efficiency and control accuracy.
Heat recovery between indoor units is carried out in the BC boxes. This allows pinch technology (heat integration) energy recovery to be diverted, reducing pipe transmission losses. Heat is redirected in the valve blocks, directly to the branch that requires it, reducing overall running costs and lifting operational COP’s.
Two-pipe VRF has significantly less electrical termination points than equivalent three-pipe systems. This reduces complexity of the initial wiring process and simplifies fault finding; reducing installation cost, time and materials. Fewer components in the system mean less plant to potentially fail in the future.
The secret of City Multi Heat Recovery Systems lies in the BC Controller. The BC Controller houses a liquid/gas separator, allowing the outdoor unit to deliver a mixture (2 phase) of hot gas for heating and liquid for cooling, all through the same pipe. Three-pipe systems allocate a pipe to each of these phases. When this mixture arrives at the BC Controller, it is separated and the correct phase delivered to each indoor unit depending on the individual requirement of either heating or cooling.