Series-301Configuration

Supported Applications

The Dwyer Series 301 is a top-mount liquid level control designed for pressurized or non-pressurized tanks and sumps where side mounting is not practical. The device utilizes a float connected to a magnetic armature that moves within a tube to operate hermetically sealed mercury switches or snap-action switch assemblies. These controls are configured for single-stage operation with fixed deadbands suitable for high or low alarms, shutdowns, and pump control in liquid level monitoring applications.

Operating Conditions & Performance

The Series 301 accommodates liquids with a specific gravity ranging from 0.5 to 1.0 and supports measurement depths up to 12 ft (from the top of the flange). The series offers fixed level changes between on and off states, varying by float type and liquid density; for example, single-stage operation provides a fixed change "D" as low as 1/2" or as high as 1-3/4" depending on configuration. Repeatability is specified at ± 1/4".

Process temperature ratings extend up to 500°F (260°C), with ambient operating temperatures rated to 212°F (100°C). Pressure and temperature limits are defined by the selected float assembly. For instance, a 7" 304 S.S. float is rated for 300 PSI @ 500°F MAX., while a 4-1/2" Copper float supports up to 150 PSI @ 300°F MAX. Specific gravity performance tables detail minimum high-level operating points and maximum low-level operating points, with tank depth requirements below the low operating point ranging from approximately 5-3/4" to 8-1/4" depending on the specific float and liquid density.

Configuration Options

The series is configurable across multiple dimensions including enclosure type, electrical circuitry, wetted materials, and process connections. Key selection parameters include:

• Enclosures: Available in General Purpose NEMA 1 (letter 'G'), Watertight NEMA 4 (letter 'WT'), Explosion-Proof NEMA 7/9 (letters 'E' or 'EV'). The EV enclosure combines weatherproof, vapor-proof, and explosion-proof construction.
• Electrical Circuits: Options include SPST (SPDT), DPDT, and DPST configurations. Switch types feature mercury contacts for high current/voltage requirements or hermetically sealed snap-action switches. Electrical ratings vary by circuit code; for example, the -4820 circuit offers 10 Amps at 120V AC, while the -7810 snap switch provides up to 12 Amps at 120V AC.
• Float Assemblies: Float sizes include 3-1/2" x 6", 4-1/2", and 7" diameters. Materials are available in Copper, 304 Stainless Steel (SS), or combinations with 316 SS stops.
• Process Connections: Standard installation uses a 3/4" NPT conduit connection which is rotatable 360°. Optional flanges include Cast Iron and Forged Steel in sizes ranging from 4" to 8", rated for pressures up to 150# or higher depending on the specific gravity and float selection.
• Special Options: Configurations may include support extensions with rod guides, semi-automatic (manual reset) operation, wide differential settings (single stage only), and 440 Volt service availability.

Key Product Differences

Variations within the Series 301 are distinguished by enclosure rating, switch technology, float material/size, and flange specifications. The model number structure follows the format: Series-Enclosure-Circuit-Float-Operating Point-Specific Gravity-Flange. For example, a unit with code -4820 utilizes an SP-ST Open on level RISE action with mercury contacts, whereas code -7810 indicates a snap-action switch. Float selection codes (e.g., 'A', 'AS', 'B') dictate the specific pressure and temperature ratings; for instance, float type 'AS' denotes a 3-1/2" x 6" 304SS assembly with galvanized steel support extension rated at 300 psi @ 500°F. Enclosure codes differentiate between general purpose ('G'), watertight ('WT'), and explosion-proof ('E', 'EV') housings, which also influence the electrical connection method (terminal board versus leads).