The A-22P-A51 is a 50 mm (1.97") plastic cold barrier extension used between a Belimo thermowell and the cable sensor probe head in chilled water and refrigeration applications. The polymer extension thermally isolates the sensor's exterior housing from the cold well — preventing condensation buildup on the probe head, connector, and cable termination, and protecting the cable jacket from thermal stress at low operating temperatures. Snaps into the standard 6 mm thermowell bore with the probe inserted through it.
Use whenever a thermowell is installed in chilled water (below ~50°F / 10°C), refrigerant, or low-temperature glycol service where condensation could form on the exposed probe head outside the well. Common applications: chilled water plant supply piping (40-45°F), low-temperature process cooling, evaporator outlet temperature monitoring. Compatible with all Belimo A-22P-A.. thermowells. Not needed for hot water or warm-side condenser water applications.
Key Features
In cold-water service, the air immediately around the sensor's probe head can drop below the room dew point — moisture condenses on the metal probe shoulder, drips into the cable strain relief, and over time causes nuisance alarms or shorted readings. The cold barrier extends the thermal break between the well tip (cold) and the probe head (room ambient), keeping the probe head above dew point.
1.97" (50 mm) length is the standard for typical HVAC chilled water applications. The barrier inserts between the thermowell's hex shoulder and the sensor's mounting collar — the probe shaft passes through the barrier's central bore.
Polymer construction provides low thermal conductivity — the barrier doesn't transmit cold to the probe head the way an all-metal extension would. Suitable for ambient conditions in typical mechanical rooms and chiller plants.
Technical Specifications
| Specification | Detail |
|---|---|
| Type | Cold barrier extension for thermowell installations |
| Length | 50 mm (1.97") |
| Material | Plastic |
| Compatible With | All Belimo A-22P-A.. thermowells with 6 mm probe bore |
| Use Case | Chilled water, refrigerant, low-temp glycol — prevents probe-head condensation |
| Mounting | Between thermowell hex shoulder and sensor mounting collar |
| Manufacturer | Belimo |
| Manufacturer Part Number | A-22P-A51 |
| Warranty | 5-year factory warranty |
Documentation
Frequently Asked Questions
Do I need a cold barrier for hot water applications?
No. The cold barrier prevents condensation that forms when the probe head sits in warm humid air next to a cold thermowell. In hot water applications, the well is warmer than ambient — no condensation, no need for the barrier. Use it only when the fluid temperature is below the ambient dew point (typically 40-50°F / 4-10°C and below).
How does it install?
Slide the cold barrier over the sensor probe before inserting the probe into the thermowell. The barrier sits between the thermowell's hex shoulder and the sensor mounting collar, with the probe passing through its central bore. Use thermal paste (A-22P-A44) in the well bore as usual.
Why plastic and not stainless steel?
Plastic has much lower thermal conductivity than stainless steel. A metal extension would conduct cold from the well to the probe head, defeating the purpose. The polymer construction provides the thermal break needed to keep the probe head above dew point.
- Sensor Type:
- Cold Barrier Extension
- Length:
- 50 mm (1.97)"
- Material:
- Plastic
- Use:
- Thermal break for cold piping
- Compatible Wells:
- All A-22P-A.. thermowells