Tjernlund Products, Inc. 950-1030 Proving Switch fan accessory

Proving Switch for HSJ Models

The Tjernlund 950-1030 Proving Switch is an accessory designed for integration with specific ventilation equipment. It is intended for installers and facility managers who require a safety interlock for compatible fan systems. This component verifies operational status before allowing connected equipment to run. It serves a precise role in air-handling installations that demand proof of airflow.

Compatibility Limited to Listed Models

Practical use is restricted to the Grainger item 4KA72 and the manufacturer model HSJ as stated in the specifications. The switch fits Tjernlund-branded units matching those references only. Installers must confirm the exact model number before purchase because no cross-reference or broader compatibility is documented. Using this switch with unlisted hardware will not provide the intended safety function.

Closed-Base Construction with HAWA Material

The unit weighs .5 units and features a closed-base design built from HAWA material. This construction protects internal contacts from dust and debris common in ventilation pathways. The enclosed housing supports reliable switching action day to day without exposure to moving air streams. Mounting provisions align with the specified HSJ series for a direct fit.