Description
The Caleffi 519502A is a 3/4″ NPT Differential Bypass Valve engineered for hydronic heating and cooling systems where precise pressure differential management is critical. By automatically bypassing excess flow when system demand drops, this valve protects circulating pumps, maintains balanced pressure across distribution circuits, and extends the service life of the entire hydronic system.
Key Features
- 3/4″ NPT connections for straightforward installation into standard hydronic piping
- Automatic differential pressure bypass operation — no external power required
- Protects circulators from deadhead conditions caused by zone valve closure
- Maintains consistent pressure differential across variable-flow hydronic systems
- Compact, durable construction suitable for residential and light commercial applications
- Caleffi quality engineering for long-term, reliable performance
Applications
- Hydronic heating and radiant floor systems
- Multi-zone systems with two-way zone valves
- Fan coil and chilled water distribution systems
- Any variable-flow hydronic circuit requiring pump protection
Product Specifications
- SKU: 519502A
- Brand: Caleffi
- Connection Size: 3/4″ NPT
- Valve Type: Differential Bypass







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