Ao Smith 100110039 Water Heater Lower Thermostat

Product Description

The AO SMITH 100110039 is a single-pole, 3-wire lower thermostat designed as a direct replacement for electric residential water heaters. It mounts in the lower element position and controls the heating element to maintain set water temperature during standby and recovery cycles. Licensed plumbers and HVAC technicians typically install this component during routine maintenance or when diagnosing inconsistent hot water output caused by thermostat failure. The single-pole configuration and 3-wire hookup keep the replacement process straightforward for qualified tradespeople familiar with electric water heater servicing.

This thermostat is intended for the lower thermostat position in electric water heaters. It is used in residential settings where the existing lower thermostat has failed or is out of calibration, resulting in reduced hot water capacity or complete loss of hot water. It ships as a direct OEM-style replacement part, making it a standard stocking item for service technicians who regularly work on electric storage water heaters.

Key Features

• Single-pole design for lower element thermostat position
• 3-wire configuration matches common electric water heater wiring layouts
• Direct replacement part for electric water heater service and repair
• Designed for lower thermostat mounting location in dual-element systems

Compatibility

Designed as an OEM-style replacement lower thermostat for electric storage water heaters requiring a single-pole, 3-wire thermostat.

Installation Notes

Installation should be performed by a licensed plumber or qualified service technician. Before beginning work, disconnect electrical power to the water heater at the breaker panel and verify the circuit is de-energized with a non-contact voltage tester. Drain pressure from the tank if required by access panel removal, and follow all applicable local electrical codes. Do not restore power until all wiring connections are secure and the access panel cover is reinstalled.

Technical Specifications

• Type: Thermostat
• Application: Electric Water Heater Lower Thermostat Replacement
• Poles: 1 (Single Pole)
• Wiring: 3 Wire

Standard Information

• Brand: AO SMITH
• Manufacturer Part Number: 100110039