Lochinvar & A.O. Smith 100093809 Door Assembly

The Lochinvar & A.O. Smith 100093809 Door Assembly is a critical combustion chamber component engineered for natural gas water heater models, specifically designed for 40S40 and 50T50 series units. As a veteran-grade manifold door assembly, this part provides the essential seal required to maintain proper atmospheric pressure and thermal containment within the burner chamber. It features an integrated door switch that serves as a vital safety interlock, ensuring the unit disables gas flow if the combustion environment is compromised or the access point is unseated.

For field technicians, this OEM replacement part is the standard for resolving issues related to failed safety switches or warped seals in FVIR (Flammable Vapor Ignition Resistant) systems. Constructed from high-grade materials to withstand consistent thermal cycling, the 100093809 assembly ensures that the manifold burner operates within manufacturer specifications for oxygen intake and exhaust. When performing a swap, verify the integrity of the combustion chamber gasket and ensure the pilot line and thermopile leads are correctly routed through the assembly to prevent premature wear or signal interference.

• Ensures a precise airtight seal for the combustion chamber to optimize burner efficiency.
• Includes a factory-calibrated natural gas door switch for reliable safety circuit continuity.
• Directly compatible with Lochinvar and A.O. Smith residential gas units (40 and 50-gallon variants).
• Constructed with heavy-duty materials to resist corrosion and thermal warping in high-heat environments.
• Simplifies manifold assembly maintenance by providing a complete, ready-to-install door interface.

What are the signs that my door assembly switch has failed?
A failed switch typically results in the water heater failing to initiate the ignition sequence or the pilot light refusing to stay lit, as the control valve will not receive the necessary signal that the chamber is safely sealed.

Can this assembly be used on Propane (LP) units?
No, the 100093809 is specifically configured for Natural Gas (NAT) systems. Using natural gas components on LP systems creates a significant safety hazard due to different pressure and orifice requirements.

Is the gasket included with the 100093809 door assembly?
Most OEM door assemblies come with the primary seal intact, but it is standard practice for contractors to inspect the manifold flange and replace any secondary gaskets to ensure a 100% leak-proof FVIR seal.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.