Mercoid Displacer Level Switches
Top mount displacer type level controls for tanks and sumps. Not affected by turbulence or pressure — excellent for viscous or dirty liquids. Single stage (Series 190) and two stage (Series 195) available.
How Displacer Level Controls Work
Mercoid® Displacer Controls use displacers that do not float on the surface of liquids, but are suspended on a coil spring inside the tank. They work on Archimedes’ principle: a submerged object weighs less in liquid than in air. As the liquid level rises around the displacer, buoyancy increases and the apparent weight of the displacer decreases, reducing spring tension. This change in tension actuates the switch.
Turbulence Resistant
Spring suspension isolates the displacer from surface turbulence that would cause false trips in float-type controls.
Pressure Independent
Operates on buoyancy, not surface position — unaffected by tank pressure changes up to 125 psig (higher ratings available).
Viscous & Dirty Liquids
Ideal for applications where floats would become coated, stuck, or give false readings due to liquid properties.
Series 190
Single Stage Top Mount Displacer Type Level Control
- Single setpoint for pump or alarm service
- Fixed or adjustable deadband
- NEMA 4X standard; explosion-proof optional
- Cable up to 100 ft (30.5 m)
- UL approved (snap switch)
- Popular model: B190-WT-7810-1.0
Series 195
Two Stage Top Mount Displacer Type Level Control
- Dual setpoints — pump AND alarm in one unit
- Fixed or adjustable deadband
- General purpose, watertight, or explosion-proof
- NPT or flange process connections
- UL approved (snap switch)
- Specific gravity 0.5 to 1.2
Common Features (Both Series)
Series Comparison
| Feature | Series 190 | Series 195 |
|---|---|---|
| Stages | Single stage | Two stage |
| Setpoints | 1 setpoint | 2 setpoints (pump + alarm) |
| Standard Enclosure | NEMA 4X watertight | General purpose, watertight, or explosion-proof |
| Process Connection | 4″ 125# cast iron flange | NPT or flange |
| Cable Length | 10 ft std, up to 100 ft | Up to 50 ft |
| Temperature Limit | 32–200°F (higher avail.) | 32–200°F (higher avail.) |
| Pressure Limit | 125 psig (higher avail.) | 125 psig (higher avail.) |
| Specific Gravity Range | 0.5 to 1.2 | 0.5 to 1.2 |
| Agency Approvals | UL (snap switch) | UL (snap switch) |
Common Specifications (Both Series)
Need help selecting the right displacer level switch?
Our team can help match the right series and configuration to your application, media, and installation requirements.