Trap failures due to freeze up drying out breakage blockage and or improper installation can compromise the seal against air ingestion through the condensate drain line.
P trap condensate drain.
If fan is located before the coil in the system the fan will push small amount of air and water down condensate drain.
What is a p trap.
There is a major difference between using p traps on sanitary applications and condensate removal from an ac unit and that is.
See below for an image of a sink p trap which works the same way.
Air conditioning units are shipped from the factory to the job site without a condensate drain trap.
If fan is located upstream of coil fan will pull water up drain line counter to water flowing down drain.
It s similar to the trap under your kitchen or bathroom sink.
Condensate comes from evaporator coil.
Traps with insufficient height between the inlet and outlet design deficiency on draw through systems can cause the drain to back up when the fan is on possibly causing.
Air was coming in from the outside and creating a dam which was preventing the con.
See water won t flow up hill so the 180 degree turn in the drain causes water to get trapped in the bottom of.
A p trap is needed to block air and allow condensate to drain properly.
P traps have to be installed on a suction system so a p trap was added.