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Thermowells: What Are They?

A Thermowell, sometimes also called a "pocket", is an accessory that is frequently used with thermometers to allow the HVAC installer to create a "sealed system". In simple terms, the Thermowell is installed in the line and then the corresponding thermometers - whether it be a liquid-in-glass thermometer, a remote reading thermometer, a bimetal or even an RTD/transmitter - have the probe installed into the Thermowell.

In using a Thermowell, the client is then able to easily replace an instrument without the need to shut down, and depending on the process media, have to drain and refill the system (e.g. when installed in a boiler or chiller system). This saves time, cost and shutdown times should a temperature instrument need replacing or upgrading.

Many Mechanical Contractors use thermowells as a cost savings feature for their clients. This is done during the initial installation of the HVAC system, and more Thermowells than temperature instruments are installed, allowing the client to install additional temperature instruments in the future without the hassle of shutting down or draining the entire system.

Thermowells are available in a myriad of materials such as: brass, lead-free brass, steel, 304 stainless steel, 316 stainless steel, Titanium, etc. The sizes and types of Thermowells can also vary depending on conditions such as flow rate, temperature and vibration. Thermowells can also be supplied with various connections that include threaded connections (NPT, BSP, BSPT, etc.), weld-in connections (no threads), sanitary connections (using a Tri-Clamp* connection) and more.

Shanghai QualityWell not only has a large selection of industrial thermometers that come standard with Thermowells, but we also manufacture Thermowells as a stand alone product. The next time you are installing temperature instrumentation in your HVAC system, consider using a Thermowell - they will save you and your client time, money and help prevent annoying downtimes.

For more information or to enquire about Thermowells for your application, please visit

*Tri-Clamp is a registered trademark of Alfa-Laval Corporation AB


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