Properly sizing and installing the suction line of a refrigeration system is very important to its overall operation. An incorrectly sized and/or installed suction line can lead to some major system problems.
The suction line needs to be sized for a minimum pressure drop through the line while maintaining an adequate refrigerant velocity to ensure good oil return to the compressor. It should be sized so its pressure drop does not exceed an equivalent of a 2°F change in saturation temperature and a minimum refrigerant velocity of 700 fpm through the horizontal sections and 1,500 fpm through the vertical sections.