no there is no formula that really works well. I always use much shorter cap tubes than others did. It depends on so many aspects. Condenser size and high pressure, the energy that the refrigerant can transport at the suction pressure, volumetric flow rate of the compressor. I use for 350 watt load singlestages with small 12ccm or 13ccm rotarys 180cm to 210cm of 1,00mm captube. For larger singlestage units with 24ccm I use 210cm to 240cm. It s all about testing with the choosen components for the unit. Regards Patrick
