The Caleffi 251004A is a solar air vent with 1/2" female NPT inlet x 3/4" male NPT outlet connections. It is used in solar thermal systems.
Best for automatic air removal at the high point of a solar collector circuit.
Specifications sourced from Caleffi North America technical literature. Last reviewed July 2026.
Key Features
Vents Air During Filling and Start-Up
A float-operated mechanism releases air as the collector loop is filled and commissioned. Caleffi instructions call for it to be installed with a shut-off valve and isolated once filling is complete.
High-Temperature Solar Duty
Built for the temperature extremes of a solar collector circuit, including stagnation, rather than standard hydronic service.
Technical Specifications
| Product Type | Solar Air Vent |
| Application | Solar Thermal |
| Series | DISCALAIR |
| Connections | 1/2" female NPT inlet x 3/4" male NPT outlet |
| Connection Type | NPT |
| Maximum operating pressure | 150 psi |
| Maximum air discharge pressure | 150 psi |
| Medium temperature range | -20 to 320 deg F (-30 to 160 deg C) |
| Shipping Weight | 1.3 lb |
Documentation
Related Products
- Caleffi 250041A : Solar Air Vent 1/2" MNPT
- Caleffi 253040 : Solar Safety Relief Valve 150 psi
- Caleffi 253042 : Solar Safety Relief Valve 36 psi
- Caleffi 253043 : Solar Safety Relief Valve 45 psi
Frequently Asked Questions
What does Caleffi 251004A do?
Caleffi 251004A vents air from a solar thermal circuit during filling and start-up. Air trapped in a collector loop blocks circulation and reduces heat transfer. Caleffi instructions call for it to be installed with a shut-off valve and isolated once the loop is filled.
Should Caleffi 251004A be left open in service?
No. Caleffi instructions call for the vent to be installed with a shut-off valve and isolated after the system is filled. Leaving it open in normal operation is not the intended use. Caleffi NA29284 is the matching shut-off valve.
Is Caleffi 251004A rated for solar stagnation temperatures?
It is built for solar thermal duty with a medium temperature range of -20 to 320 deg F (-30 to 160 deg C). Standard hydronic air vents are not rated for the temperatures a stagnating collector can reach.
What is the warranty on Caleffi 251004A?
Caleffi covers this product under its standard two-year limited warranty against defects in material and workmanship from the date of shipment. ZOT Supply is an authorized Caleffi distributor.
- Application:
- Solar Thermal
- Product Type:
- Solar Air Vent
- Series:
- DISCALAIR
- Connection Type:
- NPT
- Connections:
- 1/2 inch female NPT inlet x 3/4 inch male NPT outlet
- Max Operating Pressure:
- 150 psi
- Medium Temperature Range:
- -20 to 320 deg F (-30 to 160 deg C)
