The A-22P-A27 is a Belimo 18" (450 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 fabricated by welding the closed end to a hex-flange body — the standard construction for HVAC and light-industrial hydronic applications in brass for cost-sensitive water applications (chilled water, hot water heating, condenser water) where corrosion resistance against typical treated water is sufficient. 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 18" 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
Standard HVAC-grade fabricated thermowell — brass body with welded closed-end tip. Suitable for the operating pressures and temperatures of typical chilled water, hot water, condenser water, and light-industrial hydronic installations. Lower cost than machined alternatives.
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 (fabricated) |
| Insertion Length | 18" (450 mm) |
| Material | Brass |
| Construction | Fabricated with welded closed end |
| 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-A27 |
| Warranty | 5-year factory warranty |
Documentation
Frequently Asked Questions
What sensors fit in the A-22P-A27?
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 18" well, so use a 18" probe sensor (01CT-5..?). For wells longer than 8", custom or special-order probe lengths are required.
Why choose a fabricated thermowell?
Fabricated wells are the standard HVAC-grade choice — lower cost than machined wells, with a welded closed end. Suitable for typical chilled water, hot water, condenser water, and light-industrial hydronic applications at their normal operating pressures and temperatures. For high-pressure, glycol, or critical applications, see the machined SS alternatives in this length.
Why brass vs stainless steel?
Brass (this SKU at $105) is the lower-cost choice for typical treated water — chilled water with corrosion inhibitor, hot water heating systems, condenser water with biocide. Use stainless steel when the process fluid is corrosive (untreated water, glycol, steam, deionized water) or when galvanic compatibility with the surrounding piping matters.
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:
- 18 (450 mm)"
- Material:
- Brass
- Construction:
- Fabricated
- Process Connection:
- 1/2 NPT"
- Wrench Hex:
- 3/4";Compatible Probe=6 mm (0.24")"
- Compatible Sensors:
- 01CT / immersion temperature sensors (6mm probe)