The PL/L Vent Piping is a type of dual-wall pellet vent piping that lacks the ability to supply combustion air to the stove. It bears a resemblance to the Type B gas vent pipe, featuring twist-lock style ends, a 5/8" inner versus outer wall size difference, and a 1" clearance requirement to combustible materials. Its outer pipe is made of galvanized steel, and it is typically available in both unpainted or black painted. Despite sharing some features with the Type B gas vent pipe, the PL/L Vent Piping has some fundamental differences. The Type PL/L pipe replaces the aluminum inner wall of the B-vent with a stainless steel inner wall made of stainless steel or something similar, ensuring longevity against the mildly corrosive effects of pellet fuel flue gases.
The Type PL/L piping comes in 3" or 4" versions and must meet UL641 standards when chosen. The venting system is tested to meet a sustained temperature of 570 degrees and a flash temperature of 1,700 degrees to achieve this rating. This procedure ensures flame containment during a thermal chimney event, which is a chimney fire. It is critical to determine whether the appliance requires vent piping with sealed seams, which are pipe joints that will not leak flue gases from positive combustion pressure. Type L venting differs from B-Vent in that it can be routed in a variety of ways, giving you more creative freedom to place your vent termination. The vent pipe is under pressure from the combustion air fan within the pellet stove, forcing flue gases through the system and allowing for either vertical or horizontal discharge.