Tjernlund Products 950-0474 Prover Fan Kit PAI-4

The Tjernlund Products 950-0474 Fan Prover Kit PAI-4 is a replacement airflow control component used in combustion air intake systems to monitor and confirm proper fan operation during heating equipment startup in HVAC systems. It is placed in air supply assemblies used with boilers, furnaces, and other fuel-burning where controlled combustion airflow is required for operation. Within the system, the fan prover operates as an interlock tool that verifies adequate airflow before allowing burner ignition. It supports consistent combustion performance and helps maintain operating conditions in heating equipment.