The Caleffi 251003A is a solar air separator with 3/4" female NPT main connections with 1/2" female NPT bottom connection connections. It is used in solar thermal systems.
Best for continuous removal of entrained microbubbles that a point air vent alone will not capture.
Specifications sourced from Caleffi North America technical literature. Last reviewed July 2026.
Key Features
Separates and Vents Entrained Air
An internal element coalesces microbubbles out of the flow stream and routes them to an integral vent, removing air that a plain vent would miss.
Technical Specifications
| Product Type | Solar Air Separator |
| Application | Solar Thermal |
| Series | DISCAL |
| Connections | 3/4" female NPT main connections with 1/2" female NPT bottom connection |
| 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) |
Documentation
Related Products
- Caleffi 253040 : Solar Safety Relief Valve 150 psi
- Caleffi 253042 : Solar Safety Relief Valve 36 psi
- Caleffi 253043 : Solar Safety Relief Valve 45 psi
- Caleffi 253044 : Solar Safety Relief Valve 60 psi
Frequently Asked Questions
What does Caleffi 251003A do?
Caleffi 251003A continuously separates and discharges entrained air from a solar thermal circuit during normal operation. Air trapped in a collector loop blocks circulation and reduces heat transfer.
Should Caleffi 251003A be left open in service?
Yes. The Caleffi 251003A DISCAL is designed to continuously separate and discharge entrained air during system operation, not only during filling.
Is Caleffi 251003A 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 251003A?
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 Separator
- Series:
- DISCAL
- Connection Type:
- NPT
- Connections:
- 3/4 inch female NPT main connections with 1/2 inch female NPT bottom connection
- Max Operating Pressure:
- 150 psi
- Medium Temperature Range:
- -20 to 320 deg F (-30 to 160 deg C)
