Welcome to MDI Inc.

At Mercury Displacement Industries we manufacture the Liquid Level Control Float Switch in Wide and Narrow angle mechanical or mercury type. A wide variety of High Temperature float switches, Twin & Vertical Float switches, and cord sets available. We supply OEM's, Plumbing Supply companies, Contractors, Municipal Sewage Treatment plants, and Control Panel Specialists. We also manufacture Mercury Contactors, Relays, Tilt Switches, Solid State Relays and Timers. We now sell a variety of Grinder Pumps & Sewage Pumps.
Please call us at (800) 634-4077 / (269) 663-8574, Fax (269) 663-2924 or E-Mail Us.

Come check out our new Catalog Z!

Mercury Relays, Contactors, SSRs, Timers or Tilt Switches.

  • Mercury Relays ratings up to 100 AMP.
  • 1 through 4 pole configurations.
  • Mercury Relays, the best relays for heater loads.
  • Coil voltages up to 600 volts.
  • Hermetically sealed contacts.
  • Suitable for resistive, capacitive and inductive loads.
  • Solid State Relays up to 70 AMP
  • Many other options available.
  • Various size and AMP rated Tilt Switches

Mechanical and Mercury Liquid Level Control Float Switches.

  • Ratings up to 2HP or 25 AMP.
  • High Impact Polystyrene, ABS or High Temperature Polycarbonate ABS rated up to 221°F.
  • Any cord length available. UL Max. 99'
  • 120VAC and 240VAC series plugs, 3 pin barrel plug, or standard skive available.
  • External weights or internally weighted float switches.
  • Vertical and Twin Floats Switches
  • Many other options available.

MDI's Featured Products

MDI's Next Generation of Solid State Relays

This product is intended to replace mechanical contactors & mercury relays especially when switching is frequent. The smallest solid state relay width in the range is 2.13" (54mm) (3xDIN) and goes up to 2.84" (72 mm).

2-pole and 3-pole solid state relays switching options are available. Switch ON occurs at the voltage zero cross and switch OFF occurs at the current zero cross. Apart from resistive and slightly inductive loads, the solid state relay is certified for motor switching with associated motor ratings. Varistors are integrated for output overvoltage protection. A green LED gives indication of control voltage presence.

Non-Mercury Damper Arm Tilt Switches


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SPDT - .50” SHAFT - 18 AWG Plenum wire
5 AMPS @ 120 VAC / 5 AMP @ 30 VDC
pdf Download SP-1347 Spec Sheet


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SPDT - 1.00” SHAFT - 18 AWG Plenum wire
5 AMPS @ 120 VAC / 5 AMP @ 30 VDC
pdf Download SP-1450 Spec Sheet

2 & 3 Pole - 3-Phase Solid State Relay


P/N: 3PSS60A75
Type: 1 & 3-Phase Solid State Relay
Input range:
24-275 VAC/24 - 50 VDC
Operational ratings:
3 Pole 50 AMP @ 480 VAC 3-Phase
2 Pole 75 AMP @ 480 VAC 1-Phase
Fan also available in 120V

Grinder Pumps

Grinder Pumps

1/2 HP Effluent Pump

Champion Pump

Item: CPE5-12 V

HP: 1/2
Volt: 115
AMPS: 8.5
Cord: 20'

See more Champion Pumps