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Mercury Relay - 30 AMP - 3 Pole - 120 VAC Coil - Normally Open

SKU: 330NO-120A


Mercury Displacement Relays are all designed and built to meet the most exacting demands of industry. They have won their high place in the electrical field by doing the tough and tricky jobs that ordinary equipment could at best do in an uncertain manner. They have proved their ability to stand up under the most adverse conditions of temperature, dust and moisture, in all types of applications.

The 30-AMP model is designed to save space and simplify mounting methods. The standard mounting bracket on the three pole model allows the unit to be mounted in standard 3” snap track channel. If you do not use snap track mounting, the standard three pole bracket has key hole slots for easy mounting in any panel arrangement. The 30-AMP series is a more compact line with a well proven switch which is the heart of mercury relays. It is the same switch design that is in our 35 and 60-AMP encapsulated MDR’s, which have withstood the test of time and millions of cycles in many different applications.

330NO-120A (Resistive) SpecSheet

330NO-120AH (Gen Purpose) SpecSheet

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  • Coil Data
    • 210 Ω
    • 163 mA
    • 19.6 VA
    • 5.6 Watts
    Coil: 120V 50/60 Hz
  • Contacts:
    • 30 AMP @ 600 VAC Resistive
      • -or-
    • 30 AMP @ 480 VAC General Purpose
    Torque Specifications
    • Coil Screws: 7 in-lb
  • Coil Terminals: #6 Binding Head Screws
  • Load Terminals: #8 Binding Head Screws
  • Operate Time: 50 milliseconds
  • Release Time: 80 milliseconds
  • Contact Resistance: .003 ohm
    • After Cycling Under Load
  • Dielectric Withstand: 2500 VAC RMS
  • Longevity: Millions of Cycles
  • Temperature Range: -35°C to 85°C
  • Ratings
    • AC Resistive
      • 240 VAC @ 30 AMPS
      • 480 VAC @ 30 AMPS
      • 600 VAC @ 30 AMPS
    • Tungsten Lamp
      • 120 VAC @ 30 AMPS
    • Motor Loads
      • Not Recommended

Made in the USA

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Since 1975, MDI
Quality - Durability - Reliability

Call Us Toll Free: (800) 634-4077

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IMERC State Restrictions'

Due to mercury-added products being banned or phased out in some states, MDI cannot ship Mercury added products (Relays, Switches and Floats) to the following IMERC states:
Connecticut (CT), Minnesota (MN), Maine (ME), Massachusetts (MA), New Hampshire (NH), New York (NY), Rhode Island (RI), or Vermont (VT)

These states belong to the Interstate Mercury Education and Reduction Clearinghouse (IMERC) group, which have these restrictions.

Exemptions are currently being applied for in cases where Mercury Relays and Switches are being used to replace relays and switches in equipment originally manufactured with Mercury Relays and Switches. But, currently, MDI cannot ship into these states.

Non-Mercury Alternatives

GENERAL INFORMATION
All the care required for the manufacture of high-grade instruments is used in the manufacture of the switches. All switch parts are specially cleaned, and contamination is avoided by use of tweezers, gloves, etc., when making assemblies.
Contactors are hermetically sealed with high quality glass to metal seals.
The stainless steel tube is totally encapsulated in high grade UL approved epoxy to prevent moisture damage and voltage breakdown through the protective coating.
The coils are wound on compact nylon bobbins and molded onto the metal tube to provide minimum power loss. This allows for low coil power required to actuate the contactor. This also enables the units to handle high loads with minimum derating due to higher ambient temperatures.
Inert gases internally prevent excessive arcing between the mercury and the electrodes which enables the unit to function for millions of cycles with very low contact resistance, and minimum deterioration of the internal parts.
Available in all standard coil voltages, in single, two and three pole arrangements. Other coil voltages available upon request.
In multiple pole units each tube is actuated by its own coil. This eliminates pull-in variation between contact tubes, assuring consistent switching.

MERCURY TO METAL CONTACTOR
The load terminals are isolated from each other by the glass in the hermetic seal. "The plunger assembly", which includes the ceramic insulator, the magnetic sleeve and related parts, floats on the mercury pool. When the coil is powered causing a magnetic field, the plunger assembly is pulled down into the mercury pool which is in turn displaced and moved up to make contact with the electrode, closing the circuit between the top and bottom load terminal, which is connected to the stainless steel can. For constant duty applications, a return spring is used in place of the buffer spring.

Mercury to Metal Contactor Illustration

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PROPER FUSING IS REQUIRED
While MDIs contactors handle high inrush, such as lamp loads, very well, mercury contactors are susceptible to damage by short circuit currents, and should be fused to minimize short circuit fault currents. Fast acting UL class RK-1 and class J fuses and semiconductor I²t fuses more effectively protect relays than other fuses. These are low-peak fuses designed to limit short circuit currents. Regardless, when there is a short circuit, relay operations should be closely monitored afterward because of the possibility of concealed damage that could cause the relays to behave inconsistently.

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