How it connects
The female controller case aperture slides over the immersion well neck; a clamping collar or screw bracket engages the annular neck groove/shoulder and tightens with a screw to retain the controller without creating a fluid seal.
Male and female halves
Female opening/clamp assembly on the Aquastat controller case; mates over the male spud neck of the immersion well.
Usually connects to
- Immersion Well Neck Male
- Aquastat immersion well spud neck (Honeywell / Resideo 121371 / 123869 / 123870 series)
Common sizes
- Typically sized for standard ~3/4-inch to 1-inch (~28 mm) OD boiler immersion well necks with 3/8-inch internal bulb bore.
Where it is used
hydronic heatingboiler control systemsHVAC temperature regulation
Variations
- Resideo / Honeywell 121371AA clamp assembly
- integrated rear case clamp tab
How to recognise it
Recognized as a ~28 mm circular opening on the backplate or chassis of an Aquastat controller, fitted with a slotted clamp bracket and tightening screw that grips a grooved immersion well spud.
Often confused with
| Confused with | How to tell them apart |
|---|---|
| NPT threaded thermowell connection | The clamp connects the controller enclosure to the dry neck of the well mechanically, whereas NPT threads screw the well body into pressurized boiler piping. |
Also called
Aquastat well clampimmersion well mounting clampwell clamp assembly
Good to know
This is a dry mechanical enclosure mounting interface designed solely to hold the thermostat/controller body firmly against the immersion well so the sensor bulb remains seated inside the well.
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