To ensure the accurate tightness of fittings, it is important to use a torque wrench when installing mini-splits. In heat pump applications, the expansion and contraction of the suction and liquid lines tends to weaken the flare connections. To make sure you have a strong connection, flare connections should be made as follows.
First, set the flare in place and then add the fitting that will hold the flare.
Then, tighten the fitting by hand to set it in place.
Finally, tighten the fitting with the torque wrench in one hand while holding the fitting with a wrench in the other hand. Be sure to hold the torque wrench by the handle at the end of the wrench. This will allow for proper leverage to tighten the wrench and you will feel and hear a click when the flare is tightened completely.
By following these steps you will be able to tighten your flare connections properly to prevent leakage.