NRM Blog A Quick Crash Course in Suction P-Traps for HVACR

The HVAC/R industry has frequently quarreled about the topic of suction p-traps in risers - when are they necessary, where to place them, how large and how deep should the trap be? Of course, there is no one-size-fits-all answer. Each facility and each installation will have its own considerations and concerns. It's a great idea to be careful in this area by consulting ASHRAE and/or other trusted resources for guidance, and thinking through the dynamics of oil return, suction gas velocity, and unnecessary trapping.