Why multiple 4 way valves on VRF systems

[marc5180]

Something that has always puzzled me on VRV/F is why there are multiple 4 way valves on the inside of the condensor. These can range from being very big to very small. I've seen up to 3 4 way valves inside and i dont know why 3?

[Thermatech]

Alot of 3 pipe VRV / VRF heat recovery systems will have 2 reversing valves.
Each outdoor unit will have 2 outdoor coils.
At low load conditions only one is needed & then as load increases the outdoor unit at some point will use both coils.
For heat recovery mode the outdoor unit can use when nessessary one coil for cooling & one for heating.

The flow of refrigerant through the outdoor coils is controlled with the 4w reversing valves.
Cool only mode, heat only mode & heat recovery heating & cooling simultaneously.

For multiple outdoor units linked together each one will have 2 reversing valves.

For Mitsubishi City Multi R2 heat recovery there is only one 4w reversing valve to change from heat to cool mode at the outdoor unit.
But 4 seperate solenoid valves to control refrigerant flow through 4 sections of the outdoor coil + 1 section permanantly open.
Cool only, cool main, heat main, heat only modes.

The refrigerant flow diagrams in the service manuals are a bit complicated ( dont tell Gary )
but if you spend some time you can trace the refrigerant flow through the outdoor unit & system for all the modes.

When you fully understand the refrigerant flow in heat recovery mode then you see why consultants specify VRV / VRF for energy efficiency.

[marc5180]

Ah right, that makes a bit more sense now, thanks. Next time i'm at the condensor of one i'll try tracing the pipes as well.