The Caleffi 553542A is an AutoFill pre-adjustable automatic filling valve with a 1/2 in npt inlet x 1/2 in npt outlet connection, a pressure-reducing valve that automatically maintains the set fill pressure in a closed hydronic heating or cooling system.
Product data compiled from Caleffi North America technical documentation. Last reviewed July 2026.
Key Features
Pre-Adjustable Fill Pressure
Set the target system pressure before installation; the valve automatically reduces and holds it as the system fills.
Automatic Make-Up Water
Restores system pressure automatically after air venting or minor losses, keeping the loop full without manual attention.
Serviceable Cartridge
The internal cartridge is removable for cleaning or replacement without unsoldering the valve body.
3 - 60 psi Adjustment Range
Downstream set-point adjustable across 3 - 60 psi.
Technical Data
| Function | Pre-adjustable automatic filling valve (pressure reducing) |
|---|---|
| Connection | 1/2 in npt inlet x 1/2 in npt outlet |
| Adjustment pressure range | 3 - 60 psi |
| Factory pressure setting | 15 psi |
| Maximum upstream pressure | 230 psi |
| Maximum working temperature | 150 °F |
| Pressure gauge scale | 0 - 60 psi |
| Material | brass |
Documentation
Technical brochureRelated Products
Frequently Asked Questions
It is a pre-adjustable automatic filling valve: a pressure-reducing valve that fills a closed hydronic system to a set pressure and automatically restores it as needed.
Adjust the set point within the 3 - 60 psi range using the adjustment knob before or after installation.
No. This is the filling valve only. For code-required backflow protection, use an AutoFill Combo, which pre-assembles the fill valve with an ASSE-listed backflow preventer.
- Type:
- Automatic Filling Valve
- Series:
- AutoFill
- Connection Type:
- NPT Threaded
- Connection Size:
- 1/2 in
