Honeywell, 121371A/U, Copper Well Assembly

Honeywell 121371A/U – 1/2" NPT x 3" Copper Aquastat Well with Mounting Clip

The Honeywell 121371A/U is a 3-inch immersion well designed for use with Aquastat temperature controllers in hydronic heating systems. It provides a thermally conductive housing for the sensor bulb, allowing accurate temperature measurement while isolating the sensing element from direct exposure to pressurized system fluids.

Constructed from copper for corrosion resistance and efficient heat transfer, this well features 1/2" NPT male threads for threaded boiler tapping installation and includes a clip to secure the sensing bulb inside the well.

Product Features

• Material: Copper construction for high thermal conductivity and resistance to corrosion
• Thread Type: 1/2 inch NPT male thread for compatibility with standard boiler tappings
• Insertion Depth: 3 inches – accommodates standard 3/8 in x 2-7/8 in temperature sensing bulbs
• Mounting Hardware: Includes bulb retaining clip to hold sensor securely in place
• System Isolation: Allows bulb removal without draining the system

Technical Specifications

• Model: 121371A/U
• Insertion Length: 3 inches
• Thread Size: 1/2" NPT
• Bulb Compatibility: 3/8" diameter x 2-7/8" long immersion bulbs
• Includes: Retaining clip for sensor bulb

Installation Notes

This well should be installed by qualified plumbing or HVAC professionals. Ensure that sealing compounds or thread tape are used to prevent leaks at the boiler tapping. The sensing bulb must be fully inserted and secured using the supplied clip to maintain accurate temperature control. Verify compatibility with the Aquastat model being used.

Common Applications

• Hot water boilers using immersion-type Aquastat controllers
• Hydronic systems requiring remote temperature sensing via well insertion
• Service and retrofit installations in residential and light commercial heating systems