McDonnell & Miller 304300 Snap Switch

The McDonnell & Miller 304300, also identified as the FS1-17 Snap Switch Assembly, is the critical single pole, double throw (SPDT) replacement component designed for Series FS1, FS4-3D, FS5, FS6, and AFE-1 liquid flow switches. This industrial-grade switch is engineered specifically for high sensitivity applications in hydronic heating and HVAC systems where detecting low or moderate flow rates is vital for system protection. As an OEM replacement part, it ensures the precise restoration of the electrical circuit activation required to signal flow or no-flow conditions. Its sealed switch compartment provides essential protection against moisture and environmental variables, maintaining operational reliability in professional environments. When performing field maintenance, this snap switch facilitates accurate sensing of water, fuel oil, and other process liquids without requiring a complete housing replacement.

Key Benefits

• Broad Compatibility: Drop-in SPDT switch replacement for multiple McDonnell & Miller flow switch series including FS1, FS4-3, FS5, FS6, and AFE-1.
• Precision Control: Optimized for high sensitivity sensing in low flow HVAC and boiler control circuits.
• Rugged Hardware: Robust snap action design prevents arcing and ensures clean contact breaks under standard industrial loads.
• Sealed Construction: Protection from internal environment fluctuations ensures liquid flow switch longevity.
• Simplified Field Service: Replacing only the FS1-17 internal switch reduces downtime and avoids the need to break into the main piping run.

Common Questions

Which flow switch models use the FS1-17 (304300) assembly?
This part is the direct replacement for the internal switch mechanism in McDonnell & Miller Series FS1, FS4-3D, FS5, FS6, and AFE-1 models. Always verify your specific model number on the casting or identification plate before installation.

Is the 304300 switch compatible with viscous liquids like fuel oil?
Yes, when installed in the appropriate flow switch housing, this component is designed to handle water, fuel oil, and various oils in process work, provided the temperature does not exceed 225°F (107°C).

Can I use this for both flow and no-flow signaling?
Because this is a single pole, double throw (SPDT) switch, it can be wired to either close a circuit when flow starts or open a circuit when flow stops, making it a versatile safety control for burners and pumps.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.