Lochinvar & A.O. Smith 100108421 Lower Thermostat

For professional contractors servicing Lochinvar or A.O. Smith residential electric units, the 100108421 Lower Thermostat is the critical OEM replacement part required to maintain precise thermal regulation. This WH9 lower thermostat is the officially authorized update for the legacy 9000507005 and 9000507015 models. Engineered with a patented bimetal sensor, this component ensures maximum temperature sensitivity and responsiveness to tank conditions. It operates within a standard 240V circuit and features a high-limit safety cut-off to prevent overheating in dual-element water heaters. The unit includes a durable plastic terminal cover to protect electrical connections from dust and debris, ensuring a long-lasting, secure installation in high-demand residential environments.

Technical Specifications:

• OEM Compatibility: Replaces obsolete part numbers 9000507005 and 9000507015.
• Voltage Rating: Designed for 208V, 240V, 277V, and 480V applications.
• Temperature Range: Adjustable dial from 90°F to 150°F for custom calibration.
• Application: Specifically for the lower position in Lochinvar LTA and A.O. Smith residential electric series.
• Terminal Construction: Heavy-duty wiring terminals for positive electrical contact and reduced resistance.

Common Questions:

Is this thermostat compatible with single-element heaters?
While typically used as a lower thermostat in double-element systems, it can be used in single-element units that require a WH9 style control without an upper ECO reset.

How do I set the temperature on this model?
With the power disconnected, use a flat-head screwdriver to rotate the adjustment dial. It is professionally recommended to match the setting of the upper thermostat to ensure balanced element cycling.

Does this include the external cover?
Yes, this 100108421 thermostat comes complete with the WH9 protective cover and personnel protector as a single assembly.

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.