Hi guys first post ( and probably the last) so if this sounds silly be kind.

I'm quite new to the industry only have hands on experience. Ive installed a few VRV and VRF systems and I was wondering why Mitsi use 2 pipes but Daikin use 3. Anyone point me in the direction of where I can find more info. What is the 3rd pipe for? and is it better than a 2 pipe system. Clearly both systems work as required through a switch box ( BS BOX ) so I'm a little confused.