The Caleffi 250041A is a solar automatic air vent with a 1/2 in. male NPT connection, used in closed solar thermal circuits to release air from the fluid automatically during filling and start-up. It is rated -20 to 360 deg F (-30 to 180 deg C), 150 psi maximum working pressure and 75 psi maximum discharge pressure.
Specifications sourced from Caleffi technical brochure 01133 NA and installation instructions 28062.02. Last reviewed August 2026.
Key Features
Automatic Float-Operated Venting
A float in contact with the system fluid opens the vent as air accumulates in the body, releasing air automatically while the collector loop is filled and commissioned.
Rated to 360 deg F for Solar Duty
Caleffi states the materials allow the vent function with glycol-water temperatures up to 360 deg F (180 deg C), with a working range of -20 to 360 deg F (-30 to 180 deg C).
75 psi Maximum Discharge Pressure
The valve vents correctly as long as system pressure stays below 75 psi (5 bar). Above that the float cannot open the discharge, which is why Caleffi specifies venting during the fill phase.
Chrome-Plated Brass Body and Cover
Caleffi builds this code with a brass body and cover, both chrome plated, a high-resistance polymer float and EPDM seals.
Serviceable Without Removal
The top cover lifts off for inspection of the float mechanism, so the vent can be checked or cleaned without breaking the pipe connection.
Requires a Shut-Off Valve
Caleffi specifies pairing this vent with a shut-off valve so it can be isolated after filling. Caleffi catalog 03288 lists this code without a cock; NA29284 is the separately ordered solar-rated shut-off valve.
Technical Specifications
| Product Type | Solar Air Vent |
| Application | Closed solar thermal systems |
| Connections | 1/2 in. male NPT |
| Connection type | NPT |
| Medium | water, glycol solutions |
| Max. percentage of glycol | 50 % |
| Working temperature range | -20 to 360 deg F (-30 to 180 deg C) |
| Max. working pressure | 150 psi (10 bar) |
| Max. discharge pressure | 75 psi (5 bar) |
| Dimensions | A 1/2 in.; B 4 in.; C 2-1/8 in. dia.; D 1/2 in. (letters per dimension drawing in brochure 01133 NA) |
| Supplied with shut-off cock | no - catalog 03288 lists this code without a cock |
| Body material | brass, chrome plated |
| Cover | brass, chrome plated |
| Float | high-resistance polymer |
| Seals | EPDM |
| Manufacturer-listed weight | 0.7 lb |
Documentation
Related Products
- Caleffi NA29284 : Solar Air Vent Shut-Off Valve 1/2" FNPT x 1/2" MNPT
- Caleffi 251004A : DISCALAIR Solar Air Vent 3/4" MNPT x 1/2" FNPT
- Caleffi 251003A : DISCAL Solar Air Separator 3/4"
- Caleffi 253040 : Solar Safety Relief Valve 150 psi
Frequently Asked Questions
What does Caleffi 250041A do?
It automatically releases air from a closed solar thermal circuit. A float in contact with the fluid drops as air collects in the body, opening the vent. Trapped air blocks circulation and reduces heat transfer in a collector loop.
What is the maximum discharge pressure of Caleffi 250041A?
75 psi (5 bar). The vent only functions while system pressure stays below that figure, which is why Caleffi specifies it for the filling and start-up phase. The Caleffi 251004A DISCALAIR vents at up to 150 psi if venting at working pressure is required.
Should Caleffi 250041A be left open in service?
No. Caleffi specifies that it be installed with a shut-off valve and isolated once the loop is filled and started. Caleffi catalog 03288 lists this code without a cock; NA29284 is the separately ordered solar-rated shut-off valve.
Is Caleffi 250041A rated for solar stagnation temperatures?
Caleffi publishes a working temperature range of -20 to 360 deg F (-30 to 180 deg C) with glycol solutions to 50 %, and states the materials allow the vent to function with glycol-water temperatures up to 360 deg F (180 deg C).
How is Caleffi 250041A serviced?
The top cover removes for access to the float mechanism, so the internals can be inspected without taking the vent off the pipe. Caleffi requires an upstream shut-off valve to make this practical.
What is the warranty on Caleffi 250041A?
Caleffi North America covers this product under its two-year limited warranty against defects in material and workmanship from the date of shipment. ZOT Supply is an authorized Caleffi distributor.
- Product Type:
- Solar Air Vent
- Application:
- Solar Thermal
- Connection Type:
- NPT
- Connection Size:
- 1/2 in.
- Max Operating Pressure:
- 150 psi (10 bar)
- Max Discharge Pressure:
- 75 psi (5 bar)
- Medium Temperature Range:
- -20 to 360 deg F (-30 to 180 deg C)
- Max Glycol Concentration:
- 50 %
- Body Material:
- Brass, chrome plated
