[abakker]

Because flare fittings are a concession to make install cheaper, not better. R410a and other similar refrigerants are very high pressure, and the fittings undergo significant thermal cycles. Flared copper tube is a bad design choice. IMO, going back to brazed tubing connections is the most rational choice.

[bluGill]

brazed tubes can leak as well. I had that happen in my last house. Little leaks are hard to find, the first time I had the system refilled the tech couldn't find anything and put some sealer in. The next time the tech did the same and was disconnecting the fill lines when he saw a dark spot, then he emptied the lines and did the proper fix.

[abakker]

Sure, anything can leak. Brazed fittings when executed properly and tested are much less likely to _start leaking_. the issue is that the flares have a tendency to work harden during the constant vibration and thermal cycling and eventually give up.

[lordswork]

FWIW, I just had a heat pump installed, and the installer brazed all copper fittings. Are flared fittings often used for these installs?

[abakker]

Most mini splits use flairs, and in the context of heat pumps in the US, I see Minisplits most commonly discussed. The whole house condensers still use brazed connections.