The A-22P-A38 is a Belimo 6" (150 mm) thermowell for protecting 6 mm probe-style temperature sensors during liquid immersion. The well isolates the sensor from the process fluid, allows sensor removal and replacement without draining the system, and provides the burst-pressure barrier that prevents leakage if the probe ever fails. This well is machined from solid bar stock — drilled and turned in one piece for the highest burst-pressure rating and smoothest probe bore in stainless steel for corrosive media, glycol systems, steam, deionized water, or any installation where brass would degrade. Standard 1/2" NPT threaded process connection with a 3/4" hex (SW = 3/4") for installation wrench grip.
Designed for all Belimo cable or immersion temperature sensors with a 6 mm (0.24") probe diameter and a probe length matching the well insertion depth — the 01CT family is the most common pairing for this 6" length. Match the well length to the sensor probe length: the 01CT-5..H sensors (2" probe) pair with 2" wells; 01CT-5..L sensors (4" probe) pair with 4" wells; 01CT-5..P sensors (8" probe) pair with 8" wells. For best thermal response, fill the well with thermal paste (Belimo A-22P-A44 syringe) before inserting the probe.
Key Features
Drilled and turned from a single piece of solid stainless bar stock. No welds, no joints — eliminates the weld-zone failure mode that limits fabricated wells in high-pressure or thermally-cycled service. Use for high-pressure hydronic systems, glycol systems with frequent freeze-thaw cycling, or any application where well integrity is critical.
Standard 1/2" NPT threaded process connection — fits into the matching 1/2" NPT threadolet, tee, or weld coupling already common in HVAC piping. Use thread sealant (PTFE tape or pipe dope) rated for your process fluid and temperature on installation.
3/4" hex shoulder (SW = 3/4") above the NPT threads — accept a standard wrench for installation torque. Always tighten with a wrench on the hex, never twist by the sensor or capillary.
The well stays installed in the pipe; the sensor probe inserts into the well bore from above. To service or replace the sensor, simply withdraw the probe — no system drain-down, no isolation valves, no piping breaks. Critical for production systems where downtime is expensive.
Technical Specifications
| Specification | Detail |
|---|---|
| Type | Thermowell (machined) |
| Insertion Length | 6" (150 mm) |
| Material | Stainless Steel |
| Construction | Machined from solid bar stock |
| Process Connection | 1/2" NPT (male) |
| Wrench Hex | 3/4" (SW = 3/4") |
| Probe Bore Diameter | 6 mm (0.24") to match Belimo 6 mm probe sensors |
| Recommended Pairing | Belimo A-22P-A44 thermal paste syringe (fill well bore for best thermal response) |
| Recommended Accessory | A-22P-A51 cold barrier (50 mm plastic, for thermowells in cold piping) |
| Manufacturer | Belimo |
| Manufacturer Part Number | A-22P-A38 |
| Warranty | 5-year factory warranty |
Documentation
Frequently Asked Questions
What sensors fit in the A-22P-A38?
Any Belimo cable or immersion temperature sensor with a 6 mm (0.24") probe — the 01CT family is the most common pairing. Match the well length to the probe length: this is a 6" well, so use a 6" probe sensor (01CT-5..?). For wells longer than 8", custom or special-order probe lengths are required.
Why choose a machined thermowell?
Machined wells (this SKU at $203 for the 4" version) are drilled and turned from solid bar stock — no welds to fail, highest burst-pressure rating, smoothest probe bore. Use for high-pressure systems, glycol with freeze-thaw cycling, or any installation where well integrity is critical. Fabricated wells (less expensive) are sufficient for standard HVAC chilled/hot water and condenser water.
Why stainless steel vs brass?
Stainless steel handles corrosive media that would degrade brass: glycol systems, steam, deionized water, untreated cooling tower water, or any installation where the brass would slowly leach or pit. Brass costs less and is fine for standard treated water systems — choose by media compatibility and budget.
Do I need thermal paste in the well?
Strongly recommended. The air gap between the probe and the well's inner bore is a thermal insulator — without paste, sensor response is slower and there's a small temperature offset (the probe equilibrates against air, not the well). Belimo's A-22P-A44 syringe of thermal paste is the standard pairing. Fill the well bore with paste before inserting the probe; excess paste extrudes around the probe shoulder during insertion.
- Sensor Type:
- Thermowell
- Insertion Length:
- 6 (150 mm)"
- Material:
- Stainless Steel
- Construction:
- Machined
- Process Connection:
- 1/2 NPT"
- Wrench Hex:
- 3/4";Compatible Probe=6 mm (0.24")"
- Compatible Sensors:
- 01CT / immersion temperature sensors (6mm probe)